Patent Publication Number: US-2023146985-A1

Title: Compositions and Methods for Analyte Detection

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application which claims priority to U.S. patent application Ser. No. 17/664,095, filed on May 19, 2022, which is a continuation application which claims priority to U.S. patent application Ser. No. 17/498,829, filed on Oct. 12, 2021, which is a continuation application which claims priority to U.S. patent application Ser. No. 16/393,215, filed on Apr. 24, 2019, which is a continuation application which claims priority to U.S. patent application Ser. No. 16/255,920, filed on Jan. 24, 2019, which is a continuation application which claims priority to U.S. patent application Ser. No. 14/366,486, filed on Jun. 18, 2014, which is a National Stage Application under 35 U.S.C. 371 of co-pending PCT Application No. PCT/US12/71398 designating the United States and filed Dec. 21, 2012; which claims the benefit of U.S. Provisional Application No. 61/579,265 and filed Dec. 22, 2011 each of which are hereby incorporated by reference in their entireties. 
    
    
     GOVERNMENT SUPPORT 
     This invention was made with government support under HG005550 awarded by the National Institutes of Health. The government has certain rights in the invention. 
    
    
     SEQUENCE LISTING 
     The instant application contains a Sequence Listing which has been submitted electronically in XML format and is hereby incorporated by reference in its entirety. Said XML copy, created on Dec. 19, 2022, is named “Sequence_Listing_010498_01490_ST26” and is 113 KB in size. 
     TECHNICAL FIELD OF THE DISCLOSURE 
     The inventions provided herein relate to detection molecules or detection reagents, compositions, methods and kits for detection, identification, and/or quantification of analytes in a sample. 
     BACKGROUND 
     The need for multiplexing techniques in biology is often driven by the fact that test samples are precious and those analyzing them either do not know in advance precisely what to look for or must extract the most information from any single sample. Hence, it is desirable for clinicians and researcher to subject each sample to a large set of probes. 
     Optical readout is common in biology and can be very effective. However, it is typically limited to a relatively small number of available fluorophores or chromophores (which are referred to collectively as colors). In practice, multiplexing by fluorescence is often limited to 4 or 5 colors, which by traditional methods implies that at most 4 or 5 probes can be detected in a single sample. 
     The common approach to improving multiplexing in optical methods is to increase the number of available colors. To this end, quantum dots have been developed to provide a larger range of colors. However, in reality, it is difficult to use more than 6 quantum dot colors simultaneously. Another approach is to use mixtures or ratio of fluorophores as new colors. Such methods have extended multiplexing to hundreds of analytes, but due to the size of the labels (e.g., microbeads), the technology has thus far been limited to flow-cytometry based analyses. Yet another approach involves nanostrings, which are essentially short strings of strung-up fluorophores creating visible colorful barcodes. Unfortunately, nanostring readout requires very high-resolution imaging and a special flow apparatus. Further, the nanostrings can only be used in a sample where the probes&#39; targets are sparse, or the barcodes will overlap and create a blur. 
     A simple workaround for the limited number of colors (e.g., 4 or 5 colors) in optical readouts is to repeat the probing of the same sample with multiple small sets of different probes. For example, the assay can involve probing the sample with 4 different antibodies at a time and imaging after every assay. If the test requires probing the sample with a total of 64 antibodies, the 4-probe procedure would have to be repeated 16 times using the sample. As such, the order of detecting different target analytes in a single sample may need to be prioritized, because some target analytes in the sample can degrade during successive probings. Accordingly, there is still a strong need for accurate and sensitive methods with a high throughput for detection, identification, and/or quantification of target molecules in a sample, e.g., complex mixtures. 
     SUMMARY 
     Embodiments provided herein are based on, at least in part, the development of a multiplexed biological assay and readout, in which a multitude of detection reagents comprising one or more probes and/or probe types are applied to a sample, allowing the detection reagents to bind target molecules or analytes, which can then be optically identified in a temporally-sequential manner. In some embodiments, the multitude of detection reagents comprising one or more probes and/or probe types can be applied to a sample simultaneously. Accordingly, provided herein are methods, compositions (e.g., detection reagents) and kits for detecting multiple analytes in a sample. 
     Accordingly, one aspect provided herein relates to a method for detecting a plurality of analytes in a sample. Exemplary analytes include, without limitations, antigens, receptors, proteins, peptides, nucleic acids, sugars, lipid, carbohydrates, glycans, glycoproteins, oligonucleotides, cells, viruses, and any combinations thereof. In some embodiments, the nucleic acids can include, e.g., cellular DNA or RNA, messenger RNA, microRNA, ribosomal RNA, and any combinations thereof. A sample amenable to the methods described herein can be a sample from any sources, e.g., but not limited to biological samples, e.g., collected from organisms, animals or subjects, environmental samples, food, food byproduct, soil, archaeological samples, extraterrestrial samples, or any combinations thereof. For example, a sample can be a protein sample immobilized on a solid support including, e.g., a blotting membrane. In alternative embodiments, a sample can comprise one or more cells, one or more tissues, one or more fluids, or any combinations thereof. In some embodiments, the sample can comprise a tissue sample. In some embodiments, the sample can comprise a fluid sample. In some embodiments, a sample can comprise blood, sputum, cerebrospinal fluid, urine, saliva, sperm, sweat, mucus, nasal discharge, vaginal fluids or any combinations thereof. In some embodiments, a sample can comprise a biopsy, a surgically removed tissue, a swap, or any combinations thereof. 
     The method described herein comprises: (a) contacting the sample with a plurality of detection reagents as described herein, wherein each subpopulation of the detection reagents can target at least one different analyte; and (b) detecting in a temporally-sequential manner said plurality of the pre-determined subsequences of said detection reagents, wherein said detection of the subsequences each generates a signal signature corresponding to said subsequence, and wherein a temporal order of the signal signatures corresponding to said plurality of the subsequences of said detection reagent identifies a subpopulation of the detection reagents. In some embodiments, the temporal order of the signal signatures corresponding to said plurality of the subsequences of said detection reagent can be unique for each subpopulation of the detection reagents. 
     In some embodiments, a detection reagent described herein can target at least two distinct analytes. In some embodiments, a first subpopulation of the detection reagents can target at least one analyte different from that of a second subpopulation of the detection reagents. Accordingly, in some embodiments, the readout of the detection reagents can be distinct but overlapping. 
     In some embodiments, the method can further comprise processing the sample before contacting with the plurality of detection reagents described herein. 
     In some embodiments, the method can further comprise removing any unbound detection reagents before detection of the pre-determined subsequences in a temporally-sequential manner. 
     In some embodiments, the method can further comprise comparing the temporal order of the signal signatures with different identifiers of said at least one probe reagent, wherein an agreement between the temporal order of the signal signatures and a particular identifier of said at least one probe reagent identifies the analyte in the sample. In some embodiments, the method can further comprise measuring the intensity of the signal signatures generated from each subpopulation of the detection reagents. In some embodiments, the intensity of the signal signatures generated from each subpopulation of the detection reagents can indicate an amount of the analyte. In some embodiments, the relative intensity of the signal signatures can be used in identification of each subpopulation of the detection reagents. Thus, the intensity of the signal signatures can be used as part of a coding scheme of the detection reagents described herein. The comparing and intensity measuring steps can be performed by a computer-implemented software or algorithm. 
     Each signal signature corresponding to individual pre-determined subsequences of the detection reagent are detected in a temporally-sequential manner. In some embodiments, the detection method can include sequencing, e.g., which can be performed via any methods known in the art, including but not limited to, ligation, hybridization, synthesis, amplification, single-base extension, or any methods known in the art. In certain embodiments, the detection method can include hybridizing a decoder probe with the corresponding subsequence, wherein the decoder probe can comprise a detectable label. 
     In particular embodiments, the detection method can comprise: (a) hybridizing a set of decoder probes with a subsequence of the detection reagents, wherein each subpopulation of the decoder probes can comprise a detectable label, each detectable label producing a signal signature; (b) detecting said different signal signature produced by the hybridization of said set of decoder probes; (c) optionally removing said different signal signature produced by the hybridization of said set of decoder probes; and (d) repeating steps (a) through (c) for other subsequences of said detection reagents, thereby producing a temporal order of the signal signatures corresponding to said each detection reagent. In some embodiments, removal of the different signal signature produced by the hybridization can be performed by washing, heating, photo-bleaching, displacement (e.g., displacement of decoder probes with another reagent or nucleic acid sequence), cleavage, enzymatic digestion, quenching, chemical degradation, bleaching, oxidation, or any combinations thereof. 
     In some embodiments, each decoder probe in the set can independently have a subsequence of the detection reagents. 
     In some embodiments, each subpopulation of the decoder probes can comprise a different detectable label, each different detectable label producing a different signal signature. 
     In some embodiments, each subpopulation of the decoder probes can be complementary (e.g., partially complementary or completely complementary) to the subsequence of the detection reagents. In some embodiments, a first subpopulation and a second subpopulation of the decoder probes can be complementary (e.g., partially complementary or completely complementary) to the same subsequence of the detection reagents. In some embodiments, a first subpopulation and a second subpopulation of the decoder probes can be complementary (e.g., partially complementary or completely complementary) to distinct subsequences of the detection reagents. 
     In some embodiments involving decoder probes for detection purposes, the detectable label associated with each subpopulation of the decoder probes can comprise an optical label selected from the group consisting of a small-molecule dye, a fluorescent molecule or protein, a quantum dot, a colorimetric reagent, a chromogenic molecule or protein, a Raman label, a chromophore, and any combinations thereof. In some embodiments, the detectable label or optical label can be a fluorescent molecule or protein. 
     Types of signal signature(s) can vary upon different embodiments of detection reagents and/or decoder probes described herein. By way of example, the detection reagents and/or decoder probes can comprise an optical molecule or label, thus producing optical signatures. Examples of optical signatures can include, without limitations, signatures of fluorescent color (e.g., emission spectra under one or more excitation spectra), visible light, no-color or no-light, color (e.g., color defined by a visible light wavelength), Raman signatures, and any combinations thereof. In some embodiments, an optical signature can comprise signatures of one or more fluorescent colors, one or more visible lights, one or more no-colors or no-lights, one or more colors, one or more Raman signatures, or any combinations thereof. For example, in one embodiment, an optical signature can comprise a plurality (e.g., at least 2 or more) of fluorescent colors (e.g., fluorescent dyes). In these embodiments, the optical signatures can be detected by optical imaging or spectroscopy. 
     The spatial movement limit of an analyte in a sample allowed for a temporal detection of the detection reagents to occur can vary depending on a number of factors, including, but not limited to, presence of any distinguishable features within a field of detection, magnification used in detection (e.g., magnification of the microscope lens), density of the analytes in a sample, and any combinations thereof. In some embodiments, there can be no limit in the spatial movement of an analyte in a sample during a temporal detection of the detection reagents, for example, provided that the analyte stay within the field of detection and there is at least one same distinguishable feature in each image taken during a temporal detection so that the images can be aligned to each other based on the same distinguishable feature. In some embodiments where there is no such distinguishable feature, the spatial movement of an analyte in a sample can be less than 100 μm, including less than 50 μm, less than 25 μm, less than 10 μm, less than 1 μm or smaller, over a time period, during which a temporal detection of the detection reagents occurs. In some embodiments, the spatial movement of an analyte in a sample can be less than 1000 nm, including less than 500 nm, less than 250 nm, less than 100 nm, less than 50 nm, less than 10 nm or smaller, over a time period, during which a temporal detection of the detection reagents occurs. More importantly, the spatial movement limit of an analyte in a sample during a temporal detection is determined by the ability of matching distinguishable features between images taken during a temporal detection, which can be affected by imaging conditions. In some embodiments, the analyte can be fixed on a solid substrate or support. 
     In one aspect, embodiments provided herein relate to a detection reagent, which can be used in a multiplexing assay. The detection reagent comprises at least one probe reagent and at least one nucleic acid label, wherein said at least one nucleic acid label comprises at least one pre-determined subsequence to be detected in a temporally-sequential manner; wherein said at least one pre-determined subsequence forms an identifier of said at least one probe reagent; and wherein said at least one probe reagent and said at least one nucleic acid label are conjugated together. 
     In some embodiments, the probe reagent and the nucleic acid label can be conjugated together by at least one linker. The linker can be monovalent or multivalent. Exemplary linkers include, but are not limited to, a bond, a linker molecule, and/or a particle, for example, selected from a group consisting of a gold nanoparticle, a magnetic bead or nanoparticle, a polystyrene bead, a nanotube, a nanowire, a microparticle, and any combinations thereof. In some embodiments, the linker can be a nanoparticle. Examples of linker molecules can include, but are not limited to, a polymer, sugar, nucleic acid, peptide, protein, hydrocarbon, lipid, polyethelyne glycol, crosslinker, or combination thereof. 
     When the linker is a particle, in some embodiments, the particle can be modified by any methods known in the art. For example, the particle can be coated with streptavidin or a derivative thereof. In some embodiments, the particles can be modified or functionalized with at least one functional group. Examples of the functional groups can include, but are not limited to, amine, carboxyl, hydroxyl, aldehyde, ketone, tosyl, silanol, chlorine, hydrazine, hydrazide, photoreactive groups and any combination thereof. 
     The probe reagent of the detection reagent can be any targeting molecule of interest. Examples of the probe reagent can include, but are not limited to, a nucleic acid, an antibody or a portion thereof, an antibody-like molecule, an enzyme, a cell, a virus, an antigen, a small molecule, a protein, a peptide, a peptidomimetic, a sugar, a lipid, a glycoprotein, a peptidoglycan, an aptamer, and any combinations thereof. In some embodiments, the probe reagent can be modified by any means known to one of ordinary skill in the art. By way of example, the probe reagent can be genetically modified, or it can be biotinylated. 
     The nucleic acid label of the detection reagent can have any configuration and/or any sequence length. In some embodiments, the nucleic acid label can be single-stranded, double-stranded, partially double-stranded, a hairpin, linear, circular, branched, a concatemer (e.g., a concatemer with a 3D structure such as a rolony, i.e., rolling-circle colony, or a DNA nanoball), or any combinations thereof. In various embodiments, the nucleic acid label can be designed for minimal cross-hybridization of bases with each other. 
     In some embodiments, the nucleic acid label can be a modified nucleic acid label. An exemplary modification of the nucleic acid label includes, without limitations, conjugation of the nucleic acid label to one or more detectable molecules. The detectable molecule can include any optical molecule, including, but not limited to, a small-molecule dye, a fluorescent protein, a quantum dot, or any combinations thereof. 
     In some embodiments, the nucleic acid label can comprise at least a partially double-stranded region. For example, the nucleic acid label can be pre-hybridized with at least one optically-labeled decoder probe, e.g., to produce at least the first signal of the temporal image stack. In such embodiments, additional decoder probes can be added during the detection method described herein to hybridize with other single-strand subsequences of the nucleic acid label. 
     In some embodiments, the nucleic acid label can comprise a plurality of pre-determined subsequences. Each of the pre-determined subsequences can be independently of any length. In some embodiments, at least one of the pre-determined subsequences can comprise one or more nucleobases. In certain embodiments, at least one of the pre-determined subsequences can comprise from 1 to 100 nucleobases. 
     The pre-determined subsequences with the nucleic acid label can be conjugated together by at least one sequence linker. In some embodiments, the sequence linker can be a direct bond, e.g., a phosphoester bond, which can allow conjugation of the pre-determined subsequences to form a longer, contiguous sequence. In some embodiments, the sequence linker can be a nucleotidic linker. When the pre-determined subsequences are conjugated together by a nucleotidic linker, the nucleotidic linker can have a sequence length of at least one nucleotide. The nucleotidic linker, in some embodiments, can be single-stranded, double-stranded, partially double-stranded, a hairpin, or any combinations thereof. 
     Depending on various applications and/or assay conditions (e.g., sensitivity, sample volume/concentration), a detection signal of a probe can be amplified by conjugating the probe to a plurality of the nucleic acid labels. In such embodiments, the detection reagent can comprise one probe reagent and a plurality of nucleic acid labels. Without wishing to be limiting, in other embodiments, the detection reagent can comprise a plurality of probe reagents and a nucleic acid label. In some embodiments, the detection reagent can comprise a plurality of probe reagents and a plurality of nucleic acid labels. 
     The detection reagents and methods described herein can be used in any biological assays for detection, identification and/or quantification of target molecules or analytes in a sample. In particular embodiments, the detection reagent can be present in a soluble phase for various biological assays. By way of example only, in some embodiments, the detection reagent can be adapted for use in immunofluorescence. For example, the detection reagent adapted for use in immunofluorescence can be used to identify microbes or pathogens. In alternative embodiments, the detection reagent can be adapted for use in immunohistochemistry. For example, the detection reagent adapted for use in immunohistochemistry can be used to study tissue biopsies or cultured cells. In some embodiments, the detection reagent and the method described herein can be applied to fixed cells and/or living cells. In other embodiments, the detection reagent can be adapted for use in fluorescence in situ hybridization. In some embodiments, the detection reagent can be adapted for use in western blot. Accordingly, the detection reagent described herein can be adapted for use in various applications, e.g., but not limited to, pathogen detection and/or identification, cancer-tissue analysis and other medical pathology applications, lineage tracking of differentiating stem cells, and lineage tracking and/or identification of dendritic cells. 
     Kits for various biological assays also provided herein. In some embodiments, a kit can comprise: (a) a plurality of the detection reagents described herein or a portion thereof; and (b) at least one reagent. Examples of a reagent include, but are not limited to, a readout reagent, a wash buffer, a signal removal buffer, and any combinations thereof. 
     The kits provided herein can be used for sequencing-based readout or hybridization-based readout. In some embodiments where the kit is used for hybridization-based readout, the kit can further comprise at least one set of decoder probes complementary to at least a portion of subsequences of the detection reagents, wherein each subpopulation of the decoder probes comprises a different detectable label, each different detectable label producing a different signal signature. 
     In some embodiments, the kit can comprise a plurality of at least one component of the detection reagents, e.g., the “nucleic acid label” component of the detection reagents. In such embodiments, users can attach the provided nucleic acid labels to their probe reagents of interest to form their own detection reagents described herein. In such embodiments, the kit can further comprising at least one coupling agent that allows the user to conjugate at least one nucleic acid label to the user&#39;s probe reagents of interest. In other embodiments, the nucleic acid labels can be already attached to the pre-determined probe reagents and are thus provided to users in the form of the detection reagents that are ready to use. 
     In some embodiments, the detection reagents provided in the kit or formed by a user can be provided in a solution phase. In other embodiments, the detection reagents provided in the kit or formed by a user can be immobilized in a multi-well plate. 
     In some embodiments of any aspects described herein, the analytes or target molecules can be present in a solution phase. In some embodiments, the analytes or target molecules can be immobilized on a solid substrate or support. 
     To clarify, the compositions and methods described herein are different from the ones described in the US Patent Application No.: US 2007/0231824. The &#39;824 application discusses methods of decoding a sensor array containing immobilized microspheres, wherein the microspheres are immobilized on a solid support (e.g., an array substrate), rather than designed to be in a solution phase. As such, a sample fluid is flowed over the sensor array containing immobilized microspheres. The analytes in the sample fluid then bind to the immobilized microspheres. After binding, the sample fluid is then discarded and the immobilized microspheres are analyzed. Accordingly, the compositions and the methods described in the &#39;824 application cannot be used and detected directly on a sample (e.g., on a tissue sample) or in situ as described herein, e.g., immunofluorescence, immunohistochemistry, fluorescence in situ hybridization, or western blot. 
     Further, the assay methods described herein are also different from the general nanostring technology or other technologies as described in the U.S. Pat. No. 7,473,767, and the U.S. Patent Application No.: US 2010/0047924. The general nanostring technology and nanoreporter detection methods described in the &#39;924 application are based on determination of the “spatial location of signals” emanating from the labeled nanostrings or nanoreporters. The detection methods described in the &#39;767 patent is based on the color resulting from various ratios of different optical labels bound to the polynucleotide probes. All these previous methods will require at least a plurality of optical labels to be detected simultaneously for determination of spatial location of signals or the resultant color from various ratios of different optical labels. Accordingly, all these previous methods do not involve detection of signals in a temporally-sequential manner as described herein. Further, there are at least two disadvantages of nanostring technology based on detection of “spatial location of signals,” rather than temporal detection of signals as described herein. First, compared to the methods and detection reagents described herein, the nanostring technology generally requires very high optical magnification for spatially discerning separation of colors that are typically located very close to each other within a nanostring; thus limiting a field of view/sample size, and precision, and/or increasing instrument cost. Second, unlike the methods and detection reagents described herein, the nanostring technology generally requires a thorough control of the amount of probes used in detection, because too few probes would yield a signal that is difficult to be detected, but too many probes would increase the likelihood of probes overlapping, and thus making the readout impossible. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    shows three different embodiments of the detection reagents described herein producing distinct sequencing readout. Pathogen-specific antibodies (e.g., anti- E - Coli , anti- S. aureus , and anti- C. albicans ) are individually conjugated to a nanoparticle with at least one nucleic acid label as described herein. In accordance with one or more embodiments, the readout of the nucleic acid label can take the form of a set of optical images or spot-readings of, e.g., fluorescent or visible colors; the temporal sequence of optical images or spot-readings can then be computationally analyzed to determine the identity of the corresponding probe reagent, e.g., a pathogen-specific antibody. 
         FIG.  2    shows three different embodiments of the detection reagents described herein producing distinct sequencing readout. DNA oligonucleotides complementary to target RNA expression (e.g., OCT4, SOX2, or KLF4) are individually conjugated to a nanoparticle with at least one nucleic acid label as described herein. In accordance with one or more embodiments, the readout of the nucleic acid label can take the form of a set of optical images or spot-readings of, e.g., fluorescent or visible colors; the temporal sequence of optical images or spot-readings can then be computationally analyzed to determine the identity of the corresponding probe reagent, e.g., a DNA aptamer specific for a RNA expression. 
         FIG.  3    shows exemplary forms of a nucleic acid label of the detection reagent according to one or more embodiments described herein. 
         FIGS.  4 A and  4 B  shows two exemplary configurations of probe reagents and nucleic acid labels on particles, in accordance with one or more embodiments described herein. 
         FIG.  5    shows one embodiment of the detection reagents for an exemplary hybridization-based readout method, in accordance with one or more embodiments described herein. Pathogen-specific antibodies (e.g., anti- C. albicans ) are individually conjugated to a nanoparticle comprising at least one nucleic acid label as described herein. In accordance with one or more embodiments, the readout of the nucleic acid label can be determined by hybridizing it with a small number of, e.g., fluorescently-labeled decoder probes, imaging, and then advancing to the next set of decoder probes. In order to allow the SeqTag to be read out quickly and without the use of enzymes or chemical reactions, the DNA oligonucleotide (SeqTag) is designed to include several hybridization sites, each corresponding to a particular readout step. At each readout step, the sample is subjected to a mixture of fluorescently labeled DNA probes that could potentially bind that step&#39;s hybridization site. Each of the sites, however, is designed to bind only one of these probes, thus revealing the SeqTag&#39;s identifying code. 
         FIGS.  6 A- 6 B  show the readout images of DYNABEADS® beads (1 μm in size) localized on a sample using an exemplary hybridization-based detection method. Each bead was conjugated to one of 6 nucleic acid labels, which in turn hybridized with a different set of decoder probes conjugated to either a green, red or blank optical label during each readout stage ( FIG.  6 A : Readout stage 1;  FIG.  6 B : Readout stage 2). 
         FIG.  7    is a set of images showing that each of the detection molecule constructs (SeqTag labels) properly stained the yeast and fluorescenced in accordance with three pre-determined sets of decoder probes. SeqTag labels and oligonucleotide displacers were applied as follow:
         Step 1: Set 1 Probes only;   Step 2: Set 1 Displacement oligonucleotides and Set 2 Probes;   Step 3: Set 2 Displacement oligonucleotides and Set 3 Probes; and   Step 4: Set 3 Displacement oligonucleotides.
 
SeqTag Label and corresponding colors were as follow:
   Set 1: SeqTag 1—Green, SeqTag 2—Red, and SeqTag 3—Blue;   Set 2: SeqTag 4—Green, SeqTag 5—Red, and SeqTag 6—Blue;   Set 3: SeqTag 7—Green and SeqTag 8—Red.       

         FIG.  8    shows SeqTag readout by a displacement-hybridization experiment according to an embodiment of the method described herein. SeqTag DNA labels were incubated on a streptavidin-coated microarray. This microarray was then exposed to a sequence of fluorescently labeled detection probes and displacement oligonucleotidess, as per displacement-hybridization readout. Imaging the array after each readout step demonstrated fluorescence corresponding to the expected pattern (shown next to each image). 
         FIG.  9    is a schematic representation of displacement hybridization according to an embodiment of the method. As the readout progresses, fluorescence from prior readout steps needs to be removed so as not to obstruct the current step&#39;s signal. As illustrated in  FIG.  9   , this can be accomplished using a displacement-hybridization method: each of the SeqTag&#39;s hybridization sites can be preceded by a short “toehold” sequence. During each readout step, the sample is subjected to a mixture of “displacer” DNA oligonucleotides. One of these displacers is complementary to the preceding step&#39;s hybridization site and, with the help of the toehold, is capable of displacing the fluorescent probe that was bound there. 
         FIG.  10    is a schematic representation of a probe reagent according to an embodiment described herein. Shown is an oligonucleotide-antibody-streptavidin construct. A convenient and effective way to SeqTag-label antibodies is through a streptavidin bridge. The antibody is biotinylated and the probe DNA oligonucleotides (SeqTag) are synthesized with a 5′-biotin modification. Then, by taking advantage of streptavidin&#39;s native tetrameric form, three DNA strands are bound to each antibody. As opposed to chemical conjugation methods, which can harm the antibody, this method proves gentle enough to preserve antibody function. As shown a single streptavidin molecule (2) is bound to three of the same DNA SeqTags (1) and a single antibody (3). 
         FIG.  11    is a schematic representation of detection of an analyte by the SeqTag labeled antibody shown in  FIG.  10   . 
         FIG.  12    is a schematic representation of detection reagents for different analytes. As shown, different infectious agent (analytes) can each be assigned their own SeqTag code to enable multiplexed detection according to an embodiment described herein. 
         FIG.  13    is a schematic representation of detection reagents for SeqTagged Fluorescence in situ hybridization (FISH). FISH permits microbes to be identified based on their ribosomal RNA sequence. In the case of SeqTagged FISH, the FISH probe and its SeqTag can be synthesized as a single DNA oligonucleotides as shown. Sequences shown are, from top to bottom, SEQ ID NO: 1 (5′-CCTACACACCAGCGTGCC-3′, probe for  K. pneumonia ); SEQ ID NO: 2 (5′-CCGCACTTTCATCTTCCG-3′, probe for  H. influenza ); and SEQ ID NO: 3 (GCCAAGGCTTATACTCGC, probe for  C. albicans ). 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Described herein are methods, detection reagents (or detection molecules as used interchangeably herein) and kits for detecting a plurality of analytes in a sample. In accordance with embodiments of various aspects described herein, a probe reagent (e.g., antibody or aptamers) can be directly or indirectly labeled with a nucleic acid label. The nucleic acid information present on the nucleic acid label can then be decoded and/or detected in a temporally-sequential manner. The detection reagents and methods described herein significantly increase the number of different probes (and corresponding analytes) that can be simultaneously detected in a multiplex assay, as compared to an traditional assay where each probe is labeled with only fluorescent labels or quantum dots, and thus multiplexing is limited by the number of available and practically usable colors. Furthermore, because the detection reagents described herein are detected and/or imaged in a temporal series of steps, the number of probes (and corresponding analytes) that can be detected in a multiplex assay grows multiplicatively with the number of detection steps in a time series and the number of optical labels being used. By way of example only, 3 set of images in which 4 distinct optical labels are used can encode 4×4×4=64 distinct probe reagents (e.g., antibodies). 
     Methods of Detecting a Plurality of Analytes in a Sample 
     One aspect of the inventions provides the methods for detecting a plurality of analytes in a sample, using the detection reagents described herein. The method includes (a) contacting the sample with a composition comprising a plurality of detection reagents (which will be described in detail later), wherein each subpopulation of the detection reagents targets at least one different analyte; and (b) detecting in a temporally-sequential manner said plurality of the pre-determined subsequences of said detection reagents, wherein said detection of the subsequences each generates a signal signature corresponding to said subsequence, and wherein a temporal order of the signal signatures corresponding to said plurality of the subsequences of said detection reagent identifies a subpopulation of the detection reagents. In some embodiments, the signal signature is a temporal signature. In some embodiments, the signal signature can further comprise a spatial signature. A non-limiting example of a spatial signature includes spatial location of a signal signature. 
     In some embodiments, the temporal order of the signal signatures corresponding to the plurality of the subsequences of the detection reagent can be unique for each subpopulation of the detection reagents. In some embodiments, at least two or more signal signatures can be used to identify the same subpopulation of the detection reagents. 
     In some embodiments, a detection reagent described herein can target at least two (e.g., at least two, at least three or more) distinct analytes. In some embodiments, a first subpopulation of the detection reagents can target at least one analyte different from that of a second subpopulation of the detection reagents. By way of example only, a first subpopulation of the detection reagents can target at least analyte A and analyte B, whereas a second subpopulation of the detection reagents can target at least analyate B and analyte C. The readout of these detection reagents can be distinct but overlapping. Thus, different analytes can be identified by sampling them combinatorially and determining which one binds. 
     As used herein, the term “temporal order of the signal signatures” refers to a sequence of signal signatures determined in a temporally-sequential manner, i.e., the sequence of signal signatures is progressed through by a number of active operations performed in a temporally-sequential manner, e.g., using a different set of decoding reagents or decoder probes in each active operation. In some embodiments, using a set of decoder probes in each active operation can yield one signal signature corresponding to one subsequence of the detection reagents. 
     The composition comprising a plurality of detection reagents can exist in any format. In some embodiments, the composition comprising a plurality of detection reagents can be in a form of a solution or suspension comprising the detection reagents. In such embodiments, the composition can further comprise at least one agent. For example, without wishing to be bound, the agent can be a blocking buffer, a surfactant, unconjugated probe reagents, a stabilizer, an enzyme inhibitor, or any combinations thereof. In some embodiments where the compositions are administered in vivo, the composition can further comprise a pharmaceutically-acceptable carrier. In other embodiments, the composition comprising a plurality of detection reagents can be contained or immobilized in a device (e.g., a syringe, or a microfluidic device) or an assay or reaction vessel (e.g., solid supports such as vials, and multi-well plates). 
     As used therein, the term “contacting” refers to any suitable means for delivering, or exposing, a sample to a plurality of the detection reagents described herein. In some embodiments, the term “contacting” refers to adding the detection reagents (e.g., suspended in a solution) directly to the sample. In some embodiments, the term “contacting” can further comprise mixing the sample with the detection reagents by any means known in the art (e.g., vortexing, pipetting, and/or agitating). In some embodiments, the term “contacting” can further comprise incubating the sample together with the detection reagents for a sufficient amount of time, e.g., to allow binding of the probe reagents to the target analytes. The contact time can be of any length, depending on the binding affinities and/or concentrations of the probe reagents and/or the analytes, concentrations of the detection reagents, and/or incubation condition (e.g., temperature). For example, the contact time can be reduced if the sample and detection reagents are incubated at a higher temperature. In some embodiments, the contact time between the sample and the detection reagents can be at least about 30 seconds, at least about 1 minute, at least about 5 minutes, at least about 10 minutes, at least about 15 minutes, at least about 30 minutes, at least about 1 hour, at least about 2 hours, at least about 3 hours, at least about 4 hours, at least about 6 hours, at least about 8 hours, at least about 10 hours, at least about 12 hours, at least about 24 hours, at least about 48 hours or longer. One of skill in the art can adjust the contact time accordingly. 
     For in vivo applications, the term “contacting” can refer to administering the detection reagents to a subject, e.g., by oral administration or by injection. 
     The sample can be contacted with at least one kind of the detection reagents. In some embodiments, the sample can be contacted with at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, at least 15, at least 20, at least 30, at least 40, at least 50, at least 60, at least 70, at least 80, at least 90, at least 100 or more different kinds of the detection reagents. In some embodiments, the sample can be contacted with at least 100, at least 500, at least 1000, at least 5000, at least 10,000, at least 50,000, at least 100,000 or more different kinds of the detection reagents. Various kinds of the detection reagents described herein can differ in types of probe reagents (e.g., nucleic acids vs. antibodies), target binding domains, and/or target analytes. 
     In some embodiments, the method described herein can further comprise processing the sample before contacting with the composition comprising a plurality of detection reagents described herein. Depending on the types and/or natures of the samples and/or analytes, different sample processing techniques can be used with the methods described herein. Exemplary sample processing techniques include, but are not limited to, mechanical processing of a sample (e.g., without limitations, homogenizing, centrifuging, vortexing, sectioning and shearing), addition of at least one reagent to a sample (e.g., without limitations, lysis buffers, RNA or DNA extraction reagents, RNA or DNA digestion reagents, enzyme inhibitors, fixing agents, organic solvents, antibodies, permeabilizing agents and immunohistochemistry agents), separation of a sample (e.g., without limitations, filtering, centrifuging, electrophoresis, western blot, and Northern blot), mounting a sample on a solid support (e.g., a microscopic slide), and any combinations thereof. 
     By way of example only, if a sample is a tissue from a subject (e.g., a biopsy for immunostaining), sample processing can include, but are not limited to, tissue sectioning, mounting on a solid support, fixing the tissue, permeabilizing the tissue (if intracellular proteins are to be detected), blocking non-specific reactions with the detection reagents. In some embodiments, proteins or nucleic acids can be isolated from a tissue or fluid sample and then separated electrophoretically on a separation medium (e.g., electrophoresis gel), followed by transferring the proteins or nucleic acids to a blotting membrane. The blotting membranes containing proteins or nucleic acids can then be contacted with the detection reagents described herein. Methods of processing samples before addition of various types of probe reagents for different kinds of assays are well established in the art, and any of those methods can be performed prior to the contacting step of the methods described herein. 
     In some embodiments, the method described herein can further comprise removing any unbound detection reagents before detection of the pre-determined subsequences in a temporally-sequential manner. The term “unbound detection reagents” as used herein refers to detection reagents that have not bound to or interacted with target analytes. The unbound detection reagents can be removed from the sample by any methods known in the art, e.g., rinsing with the sample with a buffered solution at least once, at least two times, at least three times or above. 
     After the detection reagents bind to the target analytes in a sample, the nucleic acid labels of the detection reagents carrying nucleic-acid information can be decoded to allow identification of respective probe reagent(s) conjugated to them, as opposed to traditional optical labeling technologies, where an optical signature such as a fluorophore is detected in the absence of providing any nucleic acid information. In embodiments of various aspects described herein, the pre-determined subsequences within the nucleic acid labels are detected in a temporally-sequential manner. The term “temporally-sequential manner” is used in reference to detecting or decoding in a time series a plurality of the pre-determined subsequences within the nucleic acid labels of any detection reagents that are bound to target analytes in a sample. In some embodiments, one or more pre-determined subsequences within at least one nucleic acid label of each detection reagent can be detected or decoded at each time point or detection step of a time series. In some embodiments, one pre-determined subsequence within at least one nucleic acid label of each detection reagent can be detected or decoded at each time point or detection step of a time series. In some embodiments, at least one pre-determined subsequence (e.g., 1, 2, 3, 4, 5, 6, or more pre-determined subsequences) at the same corresponding location within the nucleic acid label of each detection reagent can be detected or decoded at each time point or detection step of a time series. The time period between any two time points or detection steps can be of any length, e.g., seconds, minutes and hours. For example, the time period between any two time points or detection steps can vary from about 5 seconds to about 2 hours, from about 10 seconds to about 1 hour, from about 30 seconds to about 30 mins, or from about 1 min to about 15 mins. In some embodiments, the time period between any two time points or detection steps can be less than 5 seconds. In other embodiments, the time period between any two time points or detection steps can be longer than 2 hours, longer than 4 hours, longer than 6 hours, longer than 12 hours, longer than 1 day. For example, a sample containing the detection reagents can be maintained at room temperature, at a fridge temperature (e.g., between about 0° C. and about 10° C.) or at sub-zero temperatures (e.g., between −80° C. or lower and 0° C.) during the time period between detection steps. In some embodiments, each subsequent detection step is performed substantially immediately one after another (e.g., within less than 2 seconds, less than 1 second). 
     In some embodiments, the pre-determined subsequences can be detected in any temporal orders. In some embodiments, the next pre-determined subsequence to be detected after the previous one can be located closest to the previous one. In some embodiments, the next pre-determined subsequence to be detected after the previous one can be located at least one, at least two, at least three, at least four, at least five or more pre-determined subsequences apart from the previous one. In such embodiments, any pre-determined subsequences that were bypassed in a previous detection step can be detected afterward. In some embodiments of the methods described herein, a computer-implemented software can be used to facilitate an analysis of the temporal readouts from the detection steps, e.g., re-arranging the temporal readouts in an order corresponding to their spatial locations within the nucleic acid label before further comparison and quantification analyses. 
     In some embodiments, the detection or decoding of the pre-determined subsequences can comprise nucleic acid sequencing. Methods for sequencing nucleic acids are well established to a skilled artisan, e.g., but not limited to ligation, hybridization, synthesis, amplification or single-base extension, or any combinations thereof. By way of example only, as shown in  FIG.  1    or  FIG.  2   , the nucleic acid labels each contain three pre-determined subsequences (each of one nucleotide) conjugated together by a direct bond such as a phosphodiester bond. Each sequencing step decodes or determines one nucleotide, wherein each nucleobase (A, G, C or T) generates a distinct signal signature corresponding to the nucleobase. Consequently, a temporal order or time series of the signal signatures generated from each sequencing step corresponds to the respective probe reagent, and thus identify the target analyte. Without wishing to be bound, in this embodiment, the number of sequencing steps performed is not necessarily equal to the number of the pre-determined sequences. In some embodiments, the number of sequencing steps performed can be less than the number of the pre-determined sequences. For example, as shown in  FIG.  1   , two sequencing steps could be sufficient to identify the three different probe reagents, where each base is associated with a different color. However, additional nucleic acid information can increase the accuracy of identifying different probe reagents. Further, if the sequencing of each base can yield one of 4 colors, the n-base subsequences (e.g., 3-base subsequences shown in  FIG.  1    or  FIG.  2   ) can produce 4 n  possible unique readouts, i.e., 4 n  possible distinct probe reagents can be distinguished using such detection reagents described herein. 
     While sequencing methods can convey single base difference, other detection or decoding methods that convey information by the presence or absence of entire hybridization “sites” or pre-determined subsequences on the nucleic acid label can also be used for the methods described herein. In some embodiments, the detection step can comprise hybridizing a decoder probe with a subsequence on the nucleic acid label of the detection reagent, wherein the decoder probe can comprise a detectable label. In particular embodiments, the detection method can comprise: (a) hybridizing a set of decoder probes with a subsequence of the detection reagents, wherein each subpopulation of the decoder probes can comprise a detectable label, each detectable label producing a signal signature; (b) detecting said signal signature produced by the hybridization of said set of decoder probes; and (d) repeating steps (a) and (b) for other subsequences of said detection reagents. 
     In some embodiments, each subpopulation of the decoder probes can comprise a different detectable label, each different detectable label producing a different signal signature. In these embodiments, the different signal signature produced by the hybridization of the set of decoder probes can be detected. 
     In some embodiments, each subpopulation of the decoder probes can be complementary (e.g., partially complementary or completely complementary) to the subsequence of the detection reagents. In some embodiments, a first subpopulation and a second subpopulation of the decoder probes can be complementary (e.g., partially complementary or completely complementary) to distinct subsequences of the detection reagents. In some embodiments, at least two or more subpopulations of the decoder probes can bind to the same subsequence of the detection reagents. For example, a first subpopulation and a second subpopulation of the decoder probes can be complementary (e.g., partially complementary or completely complementary) to the same subsequence of the detection reagents. 
     By way of example only,  FIG.  5    shows an exemplary detection reagent comprising anti- C. albicans  probe reagents and nucleic acid labels containing three hybridization sites or pre-determined subsequences conjugated together by sequence linkers. In the first hybridization step, a first set of decoder probes each comprising a distinct detectable label (e.g., complementary DNA readout probes shown in  FIG.  5   , each comprising a distinct optical label) is hybridized with a first pre-determined subsequence (e.g., Site 1 in  FIG.  5   ), followed by detection of a first signal signature produced by the hybridization. In the second hybridization step, a second set of decoder probes each comprising a distinct detectable label is hybridized with a second pre-determined subsequence (e.g., Site 2 in  FIG.  5   ), followed by detection of a second signal signature produced by the hybridization. The second pre-determined subsequence can be the same or different from the first pre-determined subsequence. However, in preferred embodiments, the second pre-determined subsequence is different from the first pre-determined subsequence, e.g., to minimize cross-hybridization with each other. Accordingly, the hybridization and signal detection steps are repeated for other subsequences of the detection reagents with a different set of decoder probes, thereby producing a temporal order or time series of the signal signatures corresponding to the respective probe reagent (and detection reagent). 
     As used herein, the term “decoder probe” refers an oligonucleotide with a sequence complementary to a pre-determined sequence of the nucleic acid label. By “complementary” is meant that a nucleic acid can form hydrogen bond(s) with another nucleic acid sequence by either traditional Watson-Crick or other non-traditional types. The decoder probe sequence can be completely or partially complementary to a pre-determined sequence. In some embodiments, partial complementarity is indicated by the percentage of contiguous residues in a nucleic acid molecule that can form hydrogen bonds (e.g., Watson-Crick base pairing) with a second nucleic acid sequence (e.g., 5, 6, 7, 8, 9, 10 out of 10 being 50%, 60%, 70%, 80%, 90%, and 100% complementary). “completely complementary” or 100% complementarity means that all the contiguous residues of a nucleic acid sequence will hydrogen bond with the same number of contiguous residues in a second nucleic acid sequence. Less than perfect complementarity refers to the situation in which some, but not all, nucleoside units of two strands can hydrogen bond with each other. 
     The decoder probe can have a sequence of any length. In some embodiments, the decoder probe can have a sequence length of about 1 to about 100 nucleotides, about 1 to about 50 nucleotides, about 2 to about 50 nucleotides, about 5 to about 30 nucleotides, or about 5 to about 20 nucleotides. 
     In some embodiments, the decoder probe can comprise at least one detectable label described herein. In some embodiments, the detectable label can be an optical label selected from the group consisting of a small-molecule dye, a fluorescent molecule or protein, a quantum dot, a colorimetric reagent, a chromogenic molecule or protein, a Raman label, and any combinations thereof. In some embodiments, the detectable label or optical label can be a fluorescent molecule or protein. 
     In some embodiments, the decoder probe can be modified, e.g., base modification or activated with a functional group for linkage to a detectable label. 
     The number of decoder probes in each set can vary, depending on the number of distinct subsequences in each hybridization. In some embodiments, there can be about 1 to about 100 decoder probes, about 2 to about 50 decoder probes, about 4 to about 20 decoder probes in each set. In some embodiments, there can be about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 30, 40, 50 or more decoder probes in each set. In some embodiments, while each subsequence site can hybridize with a large number of decoder probes, each set of decoder probes added in each readout step to hybridize with the subsequence site within the detection reagents can generally have as many as the number of available fluorescent colors. For example, each set of the decoder probes added in each readout step to hybridize with the subsequence site of the detection reagents can contain about 3-4 decoder probes, each of which is labeled with a distinct fluorescent color. In the case of using quantum dots or Raman labels as detection labels, there can be more than 3-4 decoder probes in each set added during each readout step. 
     Without wishing to be bound, an example of “non-overlapping nucleic acid labels” or “non-overlapping SeqTag labels” (i.e., no two decoder probes will hybridize with the same spatial site of the nucleic acid label) is shown herein for illustrative purposes. Assuming there are 12 pre-determined subsequences (e.g., nucleic acid sequences) designed for minimal cross-hybridization with each other and each others&#39; complements (e.g., A1, A2, A3, A4, B1, B2, B3, B4, C1, C2, C3, and C4). Consider a detection reagent comprising a nucleic acid label of the form: 
       5′------A[1-4]----B[1-4]----C[1-4]----3′
 
     where each position (e.g., A[1-4]) holds only one of the subsequences (e.g., A2). Now, this subsequence is decoded or detected by using decoder probes or complementary probes A1*-A4* each labeled in one of four fluorescent colors. After readout, the signal produced by the fluorophore can be removed (e.g., denaturing to undo the hybridization (and thus removing the fluorophore)) before continuing with B1*-B4*. Since each step yields one of four outcomes, this coding scheme can provide 4×4×4=64 unique readouts. These hybridization-based probes can be used to label 64 different probe reagents that can be read out in three cycles. 
     In the case where two decoder probes can overlap, a single site (e.g., A in the above nucleic acid label form), which can accept one of the different decoder probes, can be used. This single site can be read out by subjecting it to the different decoder probes, e.g., in sets of 4 using the nucleic acid label form as shown above. When the correct set is reached, the nucleic acid label, e.g., SeqTag label, should be dark (no-color). This example is not construed to be limiting and any modifications apparent to one of skill in the art is also within the scope of the inventions. 
     The advantage of readout by hybridization is that it can be quick: hybridization can take place in minutes or less. Furthermore, no chemistry or enzymes are required during the readout process, as the readout process can be performed by similar methods as used in nucleic acid sequencing, microscopy, spectroscopy, or any combinations thereof. Thus, hybridization-based readout method can reduce cost, reduce reagent storage and/or simplify the process. 
     In some embodiments of the methods described herein, there can be no limit in the spatial movement of an analyte in a sample during a temporal detection of the detection reagents, for example, provided that the analyte stay within the field of detection and there is at least one same distinguishable feature in each image taken during a temporal detection so that the images can be aligned to each other based on the same distinguishable feature. In some embodiments where there is no such distinguishable feature, the spatial movement of an analyte in a sample can be less than 100 μm, including less than 50 μm, less than 25 μm, less than 10 μm, less than 1 μm or smaller, over a time period, during which a temporal detection of the detection reagents occurs. In some embodiments, the spatial movement of an analyte in a sample can be less than 1000 nm, including less than 500 nm, less than 250 nm, less than 100 nm, less than 50 nm, less than 10 nm or smaller, over a time period, during which a temporal detection of the detection reagents occurs. More importantly, the spatial movement limit of an analyte in a sample during a temporal detection is determined by the ability of matching distinguishable features between images taken during a temporal detection, which can be affected by imaging conditions. In some embodiments, the analyte can be fixed on a solid substrate or support. In some embodiments where there is or expects to be a spatial movement of an analyte during temporal detection, the location of the analyte with respect to a sample during each detection step can be determined and registered. Such spatial shift can then be corrected afterward during signal analysis using any art-recognized computer-implemented algorithms. 
     The length of time required to perform a temporal detection of the detection reagents (e.g., the length of time it takes to obtain a temporal sequence of signal signatures for the detection reagents) can vary, depending on the number of pre-determined subsequences to be detected or read and/or the number of available detection signals (e.g., fluorescent color and/or brightfield) to be read. In some embodiments, the length of time required to perform a temporal detection of the detection reagents can be, for example, but not limited to, 5 seconds, 10 seconds, 15 seconds, 20 seconds, 30 seconds, 1 mins, 2 mins, 3 mins, 4 mins, 5 mins, 15 mins, 30 mins, 1 hour, 2 hours, 4 hours, 6 hours, or longer. 
     The detection reagents can be detected by any means available in the art that is capable of detecting the specific signals on a given detection reagent generated during sequencing- or hybridization-based methods. Where the detection reagents (e.g., hybridized with decoder probes) are fluorescently labeled, suitable consideration of appropriate excitation sources can be readily determined. Possible sources can include but are not limited to arc lamp, xenon lamp, lasers, light emitting diodes or some combination thereof. The appropriate excitation source is used in conjunction with an appropriate optical detection system, for example an inverted fluorescent microscope, an epi-fluorescent microscope or a confocal microscope. Preferably, a microscope is used that can allow for detection with enough spatial resolution to separate distinct signals from individual detection reagents. 
     Exemplary methods for detection of the detection reagents that are applicable to the methods described herein include, without limitations, the methods described in U.S. Pat. No. 7,473,767, US patent publication no. 2007/0166708, and US application number US 2010/0261026, all of which are incorporated by reference herein in its entirety. 
     Additional methods that can be used to detect optical signatures include, but are not limited to, any spectroscopic techniques, flow cytometry, or any art-recognized methods involving an optical scanner and/or a photodetector (e.g., without limitations, a charge-coupled devices, active pixel sensors, photodiode light sensors (e.g., LEDs), optical detectors, and any combinations thereof). Non-limiting examples of spectroscopic techniques can include absorption spectroscopy, emission spectroscopy, elastic scattering spectroscopy, reflection spectroscopy, impedance spectroscopy, inelastic spectroscopy, coherent or resonance spectroscopy, surface plasmon fluorescence spectroscopy, Raman spectroscopy, and any combinations thereof. Spectroscopy techniques can be used to detect light of any wavelengths, including, but not limited to, microwave, terahertz, infrared, near infrared, visible, ultraviolet, x-ray, gamma, and any combinations thereof. 
     Without wishing to be limited, in some embodiments, at least one pre-determined subsequence (e.g., individual bases or hybridization regions) can correspond to no optical signature; that is the absence of color can be considered as an additional color. In other embodiments, at least one pre-determined subsequence (e.g., individual bases or hybridization regions) can correspond to a compound optical signature, e.g., two or more simultaneous fluorescence in multiple channels during detection (e.g., by microscopy). 
     While a single area of a sample can interact with more than one probe reagents, the nucleic acid label can be designed such that any known or potential overlaps could be teased apart from the signal output. In the case where any probe may potentially overlap with all others, one can use the readout-by-hybridization variation and assign each probe a single unique hybridization sequence. Such approach can avoid multiple lengthy probe incubations and damaging stripping steps. 
     In some embodiments of the methods described herein, the signal signatures produced during any readout step (e.g., sequencing-based or hybridization-based) should be removed before advancing to the next pre-determined subsequence of the detection reagents. The removal of the signal signatures can be done by any methods known in the art, including, but not limited to, washing, heating, photo-bleaching, displacement, cleavage, enzymatic digestion, quenching, chemical degradation, bleaching, oxidation, and any combinations thereof. 
     In some embodiments, the decoder probes can be designed such that they can be simply washed out either with a plain buffer, or they can be modified by varying salt concentrations or using detergents or denaturants such as formamide or dimethyl sulfoxide (DMSO). 
     In other embodiments, the fluorescence or color signature of a readout step can be attenuated or eliminated by photo-bleaching the signal using sufficient optical exposure. In alternative embodiments, the fluorescence or color signature of a readout step can be attenuated or eliminated by subjecting the fluorescence or color signature to chemical degradation under appropriate conditions, e.g., using a reducing agent or oxidizing solution such as 0.01 M sodium periodate. 
     In some embodiments, the decoder probes can be displaced from their hybridization sites by introducing other reagents or probe displacers that have stronger binding affinities to those same sites. This can be done, for example, by using nucleic acid sequences that are longer than and/or have better complementarity than the decoder probe sequences. For example, to create “better complementarity” of the probe displacers, in some embodiments, mismatches can be seeded in the hybridization region. In other embodiments, the hybridization region can be preceded and/or post-ceded with a “toe-hold” of around 3-8 bases (e.g., 6 bases). In such embodiments, the “better complementarity” of the probe displacer can be outside of the hybridization region, which can make the design of the hybridization regions easier. 
     In some embodiments, enzymes can be used to displace, digest, cut and/or cleave the detectable labels, the decoder probe sequence, the hybridized complex (formed by the decoder probe and pre-determined subsequence), and/or the cleavable sequence linker to the hybridized complex, in order to remove the signal signatures. One example is to introduce a deoxyuridine into the decoder probe. This modified base can be cleaved using the enzyme mix known as USER, thereby cutting the decoder probe sequence into two parts. Since each part is now shorter, it is characterized by a lower melting temperature and can melt off the hybridization sites of the detection reagents. Alternatively, one of skill in the art can employ one of numerous art-recognized sequence-specific nucleases or restriction enzymes, which can cut either the decoder probe sequence, the pre-determined subsequence that has been hybridized with decoder probes, the cleavable sequence linker attached to the hybridized subsequence and/or the hybridized complex thereof, thereby removing the signal signature. 
     In some embodiments, thermal denaturing can be used to remove the signal signature from a previous readout. In some embodiments where sequencing is involved, thermal denaturing can be reduced or avoided by using a sequencing-by-ligation approach and by setting the nucleic acid label base that immediately follows the sequencing primer (in the direction of ligation) to an adenine. Correspondingly, the ligation probes should then include a (deoxy-)uracil in the primer-proximal position. Without wishing to be bound by theory, an enzyme such as USER, which cleaves DNA at uracils can be used to remove the ligation probe and ready the system for the next sequencing step. These fragments will have lower melting temperatures than their parent probes, and these temperatures can be designed to fall below the operating temperature (or require an acceptable denaturing temperature). 
     After detection of the pre-determined subsequences is completed in a temporally-sequential manner, in some embodiments, the method described herein can further comprise comparing the temporal order of the signal signatures with different identifiers of said at least one probe reagent, wherein an agreement between the temporal order of the signal signatures and a particular identifier of said at least one probe reagent identifies the analyte in the sample. In some embodiments, the method can further comprise measuring the intensity of the signal signatures generated from each subpopulation of the detection reagents. In some embodiments, the intensity of the signal signatures generated from each subpopulation of the detection reagents can indicate an amount of the analyte. In some embodiments, the relative intensity of the signal signatures can be used in identification of each subpopulation of the detection reagents. Thus, the intensity of the signal signatures can be used as part of a coding scheme of the detection reagents described herein. The comparing and intensity measuring steps can be performed, e.g., by a computer-implemented software or algorithm. 
     Types of signal signature(s) can vary upon different embodiments of detection reagents and/or decoder probes described herein. As used herein, the term “signal signature” refers to a change in, or occurrence of, a response or indicator that is detectable either by observation or instrumentally. In certain instances, the signal signature is fluorescence or a change in fluorescence, e.g., a change in fluorescence intensity, fluorescence excitation or emission wavelength distribution, fluorescence lifetime, and/or fluorescence polarization. By way of example only, the fluorescence can be produced by binding a fluorophore to a decoder probe, and/or by detecting the hybridization using a fluorescent dye, e.g., SYBR Gold, that lights up when nucleic acid sequence becomes double-stranded. In certain other instances, the signal signature can be radioactivity (i.e., radiation), including alpha particles, beta particles, nucleons, electrons, positrons, neutrinos, and gamma rays emitted by a radioactive substance such as a radionuclide. By way of example, the detection reagents and/or decoder probes can comprise an optical molecule or label, thus producing optical signatures. Examples of optical signatures can include, without limitations, signatures of fluorescent color, visible light, no-color, and any combinations thereof. In such embodiments, the optical signatures can be detected by optical imaging or spectroscopy. 
     Detection Reagents (or Detection Molecules as Used Interchangeably Herein) 
     Another aspect provided herein is a detection reagent, which can be, for example, used in the methods described herein for any multiplexing assays. The detection reagent comprises at least one probe reagent and at least one nucleic acid label, wherein said at least one nucleic acid label comprises at least one pre-determined subsequence to be detected in a temporally-sequential manner; wherein said at least one pre-determined subsequence forms an identifier of said at least one probe reagent; and wherein said at least one probe reagent and said at least one nucleic acid label are conjugated together. 
     The detection reagents described herein can exist in different forms. By way of example only, in some embodiments, the detection reagent can be a detection molecule. In some embodiments, the detection reagent can be a detection particle. In some embodiments, the detection reagent can be multi-molecular. 
     As used herein, the term “conjugated” refers to two molecules being linked to each other, e.g., attaching a probe reagent to a nucleic acid label. The conjugation process can be performed, e.g., via a chemical reaction, or via a linker, which will be described later. 
     Depending on various applications and/or assay conditions (e.g., sensitivity, sample volume/concentration), a readout signal of a detection reagent can be amplified by increasing the number of the nucleic acid labels present in the detection reagent, e.g., by conjugating at least one probe reagent to a plurality of nucleic acid labels. In such embodiments, a plurality of the nucleic acid labels present in the detection reagent can range from about 2 to about 100,000, about 2 to about 10,000, about 2 to about 1,000, or about 2 to about 100. In some embodiments where the detection reagent comprises a particle as a hub, the number of possible nucleic acid labels present in the detection reagent can depend on the size of a particle. Generally, the larger the particle it is, the more nucleic acid labels can be incorporated into the detection reagent. For example, a particle of about 1-2 μm in size can allow incorporation of about 100,000 nucleic acid labels into the detection reagent. In some embodiments, there can be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 50, 100, 500, 1000, 5000, 10000, 50000, 100000 nucleic acid labels present in the detection reagent. One of skill in the art can determine the optimum number of nucleic acid labels present the detection reagent without any undue experimentation. 
     The detection reagents described herein can be used in any biological assays for detection, identification and/or quantification of target molecules or analytes, including counting marked cells such as bacteria or cancer cells, in a sample. By way of example only, in some embodiments, the detection reagent can be adapted for use in immunofluorescence. In alternative embodiments, the detection reagent can be adapted for use in immunohistochemistry. In other embodiments, the detection reagent can be adapted for use in fluorescence in situ hybridization. In some embodiments, the detection reagent can be adapted for use in western blot. Depending on the nature of the sample and/or applications, the detection reagent can be adapted to be in any format, e.g., immobilized on a solid support, or in a solution or suspension phase. In certain embodiments, the detection reagent can be adapted to be present in a solution or suspension phase. The phrase “in a solution or suspension phase” as used herein generally refers to suspending the detection reagents in a liquid fluid, e.g., an aqueous buffer solution. Additional applications of the detection reagents and/or methods described herein will be discussed. 
     Probe Reagents (or Probe Molecules as Used Interchangeably Herein) 
     Each of the detection reagents described herein can comprise any number of probe reagents. In some embodiments, the detection reagent can comprise one or more probe reagents, e.g., at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10 or more probe reagents. In one embodiment, the detection reagent can comprise one probe reagent. In other embodiments, the detection reagent can comprise a plurality of probe reagents, e.g., ranging from about 2 to about 100,000 probe reagents, about 2 to about 10,000 probe reagents, about 2 to about 1,000 probe reagents, or about 2 to about 100 probe reagents. In some embodiments where the detection reagent comprises a particle as a hub, the number of possible probe reagents present in the detection reagent can depend on the size of a particle. Generally, the larger the particle it is, the more probe reagents can be incorporated into the detection reagent. For example, a particle of about 1-2 μm in size can allow incorporation of about 100,000 probe reagents into the detection reagent. In some embodiments, there can be about 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 50, 100, 500, 1000, 5000, 10000, 50000, 100000 probe reagents present in the detection reagent. One of skill in the art can determine the optimum number of probe reagents present the detection reagent without any undue experimentation. 
     As used interchangeably herein, the term “probe,” “probe reagent” or “probe molecule” refers to an entity (e.g., but not limited to, a molecule, a particle, a composite entity, or a multi-molecular entity) that interacts with or binds to a target molecule or an analyte for the analysis of the target or the analyte. Typically the nature of the interaction or binding is noncovalent, e.g., by hydrogen, electrostatic, or van der Waals interactions, however, binding can also be covalent. Probe reagents can be entities (e.g., but not limited to, molecules, a particles, composite entities, or multi-molecular entities) capable of undergoing binding or molecular recognition events with target molecules. Probe reagents can be naturally-occurring, recombinant or synthetic. Examples of the probe reagent can include, but are not limited to, a nucleic acid, an antibody or a portion thereof, an antibody-like molecule, an enzyme, a cell, an antigen, a small molecule, a protein, a peptide, a peptidomimetic, an aptamer, and any combinations thereof. By way of example only, in immunohistochemistry, the probe reagent can include an antibody specific to the target antigen to be analyzed. An ordinary artisan can readily identify appropriate probe reagents for the target molecules or analytes of interest to be detected in various bioassays. In some embodiments, the probe reagent can be multi-molecular. For example, in one embodiment, the probe reagent can comprise a particle, an antibody, biotin and/or streptavidin, or any combinations thereof. 
     In some embodiments, the probe reagents can be modified by any means known to one of ordinary skill in the art. Methods to modify each type of probe reagents are well recognized in the art. Depending on the types of probe reagents, an exemplary modification includes, but is not limited to genetic modification, biotinylation, labeling (for detection purposes), chemical modification (e.g., to produce derivatives or fragments of the probe reagent), and any combinations thereof. In some embodiments, the probe reagent can be genetically modified. In some embodiments, the probe reagent can be biotinylated. 
     As used herein, the terms “proteins” and “peptides” are used interchangeably herein to designate a series of amino acid residues connected to the other by peptide bonds between the alpha-amino and carboxy groups of adjacent residues. The terms “protein”, and “peptide”, which are used interchangeably herein, refer to a polymer of protein amino acids, including modified amino acids (e.g., phosphorylated, glycated, etc.) and amino acid analogs, regardless of its size or function. Although “protein” is often used in reference to relatively large polypeptides, and “peptide” is often used in reference to small polypeptides, usage of these terms in the art overlaps and varies. The term “peptide” as used herein refers to peptides, polypeptides, proteins and fragments of proteins, unless otherwise noted. The terms “protein” and “peptide” are used interchangeably herein when referring to a gene product and fragments thereof. Thus, exemplary peptides or proteins include gene products, naturally occurring proteins, homologs, orthologs, paralogs, fragments and other equivalents, variants, fragments, and analogs of the foregoing. 
     As used herein, the term “peptidomimetic” refers to a molecule capable of folding into a defined three-dimensional structure similar to a natural peptide 
     The term “nucleic acids” used herein refers to polymers (polynucleotides) or oligomers (oligonucleotides) of nucleotide or nucleoside monomers consisting of naturally occurring bases, sugars and intersugar linkages. The term “nucleic acid” also includes polymers or oligomers comprising non-naturally occurring monomers, or portions thereof, which function similarly. Exemplary nucleic acids include, but are not limited to, deoxyribonucleic acid (DNA), ribonucleic acid (RNA), locked nucleic acid (LNA), peptide nucleic acids (PNA), and polymers thereof in either single- or double-stranded form. Locked nucleic acid (LNA), often referred to as inaccessible RNA, is a modified RNA nucleotide. The ribose moiety of an LNA nucleotide is modified with an extra bridge connecting the 2′ oxygen and 4′ carbon. The bridge “locks” the ribose in the 3′-endo conformation. LNA nucleotides can be mixed with DNA or RNA residues in the oligonucleotide whenever desired. Such LNA oligomers are generally synthesized chemically. Peptide nucleic acid (PNA) is an artificially synthesized polymer similar to DNA or RNA. DNA and RNA have a deoxyribose and ribose sugar backbone, respectively, whereas PNA&#39;s backbone is composed of repeating N-(2-aminoethyl)-glycine units linked by peptide bonds. PNA is generally synthesized chemically. Unless specifically limited, the term “nucleic acids” encompasses nucleic acids containing known analogs of natural nucleotides, which have similar binding properties as the reference nucleic acid and are metabolized in a manner similar to naturally occurring nucleotides. Unless otherwise indicated, a particular nucleic acid sequence also implicitly encompasses conservatively modified variants thereof (e.g., degenerate codon substitutions) and complementary sequences, as well as the sequence explicitly indicated. Specifically, degenerate codon substitutions may be achieved by generating sequences in which the third position of one or more selected (or all) codons is substituted with mixed-base and/or deoxyinosine residues (Batzer, et al., Nucleic Acid Res. 19:5081 (1991); Ohtsuka, et al., J. Biol. Chem. 260:2605-2608 (1985), and Rossolini, et al., Mol. Cell. Probes 8:91-98 (1994)). The term “nucleic acid” should also be understood to include, as equivalents, derivatives, variants and analogs of either RNA or DNA made from nucleotide analogs, and, single (sense or antisense) and double-stranded polynucleotides. 
     In some embodiments, the term “nucleic acid” described herein can include a modified nucleic acid. Modified nucleic acids are well known in the art. Thus, a nucleic acid described herein can comprise one or more nucleic acid modifications known in the art. For example, the nucleic acid can comprise one or more nucleic acid modifications selected from the group consisting of internucleotide linkage modifications (intersugar linkage modifications), sugar modifications, nucleobase modifications, backbone modifications/replacements, and any combinations thereof. Exemplary internucleotide linkage modifications include, but are not limited to, phosphorothioate, phosphorodithioate, phosphotriester (e.g. alkyl phosphotriester), aminoalkylphosphotriester, alkyl-phosphonate (e.g., methyl-phosphonate), selenophosphate, phosphoramidate (e.g., N-alkylphosphoramidate), boranophosphonate, and the like. Exemplary sugar modifications include, but are not limited to, 2′-O-Me (2′-O-methyl), 2′-O-MOE (2′-O-methoxyethyl), 2′-F, 2′-O-[2-(methylamino)-2-oxoethyl] (2′-O-NMA), 2′-S-methyl, 2′-O—CH 2 -(4′-C) (LNA), 2′-O—CH 2 CH 2 -(4′-C) (ENA), 2′-O-aminopropyl (T-O-AP), 2′-O-dimethylaminoethyl (2′-O-DMAOE), 2′-O-dimethylaminopropyl (T-O-DMAP), 2′-O-dimethylaminoethyloxyethyl (2′-O-DMAEOE), arabinose sugar, and the like. Exemplary nucleobase modifications include, but are not limited to, inosine, xanthine, hypoxanthine, nubularine, isoguanisine, tubercidine, 5-methylcytosine (5-me-C); 5-hydroxymethyl cytosine; xanthine; hypoxanthine; 2-aminoadenine; 6-methyl and other 6-alkyl derivatives of adenine and guanine; 2-propyl and other 2-alkyl derivatives of adenine and guanine; 2-thiouracil; 2-thiothymine; 2-thiocytosine; 5-propynyl uracil; 5-propynyl cytosine; 6-azouracil; 6-azocytosine; 6-azothymine; 5-uracil (pseudouracil); 4-thiouracil; 8-halo, 8-amino, 8-thiol, 8-thioalkyl, 8-hydroxyl and other 8-substituted adenines and guanines; 5-halo particularly 5-bromo, 5-trifluoromethyl and other 5-substituted uracils and cytosines; 7-methyl and other 7-alkyl derivatives of adenine and guanine; 8-azaguanine; 8-azaadenine; 7-deazaguanine; 7-deazaadenine; 3-deazaguanine; 3-deazaadenin; universal base; and any combinations thereof. Exemplary backbone modifications include, but are not limited to, morpholino, cyclobutyl, pyrrolidine, peptide nucleic acid (PNA), aminoethylglycyl PNA (aegPNA), backnone-extended pyrrolidine PNA (bepPNA), and the like. 
     The term “enzymes” as used here refers to a protein molecule that catalyzes chemical reactions of other substances without it being destroyed or substantially altered upon completion of the reactions. The term can include naturally occurring enzymes and bioengineered enzymes or mixtures thereof. Examples of enzyme families include kinases, dehydrogenases, oxidoreductases, GTPases, carboxyl transferases, acyl transferases, decarboxylases, transaminases, racemases, methyl transferases, formyl transferases, and α-ketodecarboxylases. 
     As used herein, the term “aptamers” means a single-stranded, partially single-stranded, partially double-stranded or double-stranded nucleotide sequence capable of specifically recognizing a selected non-oligonucleotide molecule or group of molecules. In some embodiments, the aptamer recognizes the non-oligonucleotide molecule or group of molecules by a mechanism other than Watson-Crick base pairing or triplex formation. Aptamers can include, without limitation, defined sequence segments and sequences comprising nucleotides, ribonucleotides, deoxyribonucleotides, nucleotide analogs, modified nucleotides and nucleotides comprising backbone modifications, branchpoints and nonnucleotide residues, groups or bridges. Methods for selecting aptamers for binding to a molecule are widely known in the art and easily accessible to one of ordinary skill in the art. 
     As used herein, the term “antibody” or “antibodies” refers to an intact immunoglobulin or to a monoclonal or polyclonal antigen-binding fragment with the Fc (crystallizable fragment) region or FcRn binding fragment of the Fc region. The term “antibodies” also includes “antibody-like molecules”, such as fragments of the antibodies, e.g., antigen-binding fragments. Antigen-binding fragments can be produced by recombinant DNA techniques or by enzymatic or chemical cleavage of intact antibodies. “Antigen-binding fragments” include, inter alia, Fab, Fab′, F(ab′)2, Fv, dAb, and complementarity determining region (CDR) fragments, single-chain antibodies (scFv), single domain antibodies, chimeric antibodies, diabodies, and polypeptides that contain at least a portion of an immunoglobulin that is sufficient to confer specific antigen binding to the polypeptide. Linear antibodies are also included for the purposes described herein. The terms Fab, Fc, pFc′, F(ab′) 2 and Fv are employed with standard immunological meanings (Klein, Immunology (John Wiley, New York, N.Y., 1982); Clark, W. R. (1986) The Experimental Foundations of Modern Immunology (Wiley &amp; Sons, Inc., New York); and Roitt, I. (1991) Essential Immunology, 7th Ed., (Blackwell Scientific Publications, Oxford)). Antibodies or antigen-binding fragments specific for various antigens are available commercially from vendors such as R&amp;D Systems, BD Biosciences, e-Biosciences and Miltenyi, or can be raised against these cell-surface markers by methods known to those skilled in the art. 
     As used herein, the term “Complementarity Determining Regions” (CDRs; i.e., CDR1, CDR2, and CDR3) refers to the amino acid residues of an antibody variable domain the presence of which are necessary for antigen binding. Each variable domain typically has three CDR regions identified as CDR1, CDR2 and CDR3. Each complementarity determining region may comprise amino acid residues from a “complementarity determining region” as defined by Kabat (i.e. about residues 24-34 (L1), 50-56 (L2) and 89-97 (L3) in the light chain variable domain and 31-35 (H1), 50-65 (H2) and 95-102 (H3) in the heavy chain variable domain; Kabat et al., Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, National Institutes of Health, Bethesda, Md. (1991)) and/or those residues from a “hypervariable loop” (i.e. about residues 26-32 (L1), 50-52 (L2) and 91-96 (L3) in the light chain variable domain and 26-32 (H1), 53-55 (H2) and 96-101 (H3) in the heavy chain variable domain; Chothia and Lesk J. Mol. Biol. 196:901-917 (1987)). In some instances, a complementarity determining region can include amino acids from both a CDR region defined according to Kabat and a hypervariable loop. 
     The expression “linear antibodies” refers to the antibodies described in Zapata et al; Protein Eng., 8(10):1057-1062 (1995). Briefly, these antibodies comprise a pair of tandem Fd segments (VH-CH1-VH-CH1) which, together with complementary light chain polypeptides, form a pair of antigen binding regions. Linear antibodies can be bispecific or monospecific. 
     The expression “single-chain Fv” or “scFv” antibody fragments, as used herein, is intended to mean antibody fragments that comprise the VH and VL domains of antibody, wherein these domains are present in a single polypeptide chain. Preferably, the Fv polypeptide further comprises a polypeptide linker between the VH and VL domains which enables the scFv to form the desired structure for antigen binding. (Pl{umlaut over (υ)}ckthun, The Pharmacology of Monoclonal Antibodies, vol. 113, Rosenburg and Moore eds., Springer-Verlag, New York, pp. 269-315 (1994)). 
     The term “diabodies,” as used herein, refers to small antibody fragments with two antigen-binding sites, which fragments comprise a heavy-chain variable domain (VH) Connected to a light-chain variable domain (VL) in the same polypeptide chain (VH—VL). By using a linker that is too short to allow pairing between the two domains on the same chain, the domains are forced to pair with the complementary domains of another chain and create two antigen-binding sites. (EP 404,097; WO 93/11161; Hollinger et ah, Proc. Natl. Acad. Sd. USA, P0:6444-6448 (1993)). 
     As used herein, the term “small molecules” refers to natural or synthetic molecules including, but not limited to, peptides, peptidomimetics, amino acids, amino acid analogs, polynucleotides, polynucleotide analogs, aptamers, nucleotides, nucleotide analogs, organic or inorganic compounds (i.e., including heteroorganic and organometallic compounds) having a molecular weight less than about 10,000 grams per mole, organic or inorganic compounds having a molecular weight less than about 5,000 grams per mole, organic or inorganic compounds having a molecular weight less than about 1,000 grams per mole, organic or inorganic compounds having a molecular weight less than about 500 grams per mole, and salts, esters, and other pharmaceutically acceptable forms of such compounds. 
     The term “cells” used herein refers to any cell, prokaryotic or eukaryotic, including plant, yeast, worm, insect and mammalian. Mammalian cells include, without limitation; primate, human and a cell from any animal of interest, including without limitation; mouse, hamster, rabbit, dog, cat, domestic animals, such as equine, bovine, murine, ovine, canine, feline, etc. The cells may be a wide variety of tissue types without limitation such as; hematopoietic, neural, mesenchymal, cutaneous, mucosal, stromal, muscle spleen, reticuloendothelial, epithelial, endothelial, hepatic, kidney, gastrointestinal, pulmonary, T-cells etc. Stem cells, embryonic stem (ES) cells, ES-derived cells and stem cell progenitors are also included, including without limitation, hematopoeitic, neural, stromal, muscle, cardiovascular, hepatic, pulmonary, gastrointestinal stem cells, etc. Yeast cells may also be used as cells in some embodiments of the methods described herein. In some embodiments, the cells can be ex vivo or cultured cells, e.g. in vitro. For example, for ex vivo cells, cells can be obtained from a subject, where the subject is healthy and/or affected with a disease. Cells can be obtained, as a non-limiting example, by biopsy or other surgical means know to those skilled in the art. 
     As used herein, the term “antigens” refers to a molecule or a portion of a molecule capable of being bound by a selective binding agent, such as an antibody, and additionally capable of being used in an animal to elicit the production of antibodies capable of binding to an epitope of that antigen. An antigen may have one or more epitopes. The term “antigen” can also refer to a molecule capable of being bound by an antibody or a T cell receptor (TCR) if presented by MHC molecules. The term “antigen”, as used herein, also encompasses T-cell epitopes. An antigen is additionally capable of being recognized by the immune system and/or being capable of inducing a humoral immune response and/or cellular immune response leading to the activation of B- and/or T-lymphocytes. This may, however, require that, at least in certain cases, the antigen contains or is linked to a Th cell epitope and is given in adjuvant. An antigen can have one or more epitopes (B- and T-epitopes). The specific reaction referred to above is meant to indicate that the antigen will preferably react, typically in a highly selective manner, with its corresponding antibody or TCR and not with the multitude of other antibodies or TCRs which may be evoked by other antigens. Antigens as used herein may also be mixtures of several individual antigens. 
     In some embodiments, the probe reagent can be an antibody or a portion thereof, or an antibody-like molecule. In such embodiments, the probe reagents can be used to, for example, detect and/or identify pathogen type or species, the presence of cell or disease markers, cellular protein expression levels, phosphorylation or other post-translation modification state, or any combinations thereof. By way of example only,  FIG.  1    shows three different embodiments of the detection reagents comprising at least one (e.g., 1, 2, 3, 4, 5 or more) pathogen-specific antibodies (e.g., anti- E. coli , anti- S. aureus , and anti- C. albicans ). 
     In some embodiments, the probe reagent can be a nucleic acid (e.g., DNA, RNA, LNA, PNA, or any combinations thereof). In such embodiments, the nucleic acids can be used to determine, for example, the existence of characteristic cellular DNA or RNA sequences (such as in fluorescent in situ hybridization), RNA expression levels, miRNA presence and expression, and any combinations thereof, in various applications, e.g., for pathogen detection and/or identification. 
     In some embodiments, the probe reagent can be a protein or a peptide. In such embodiments, the protein or peptide can be essentially any proteins with known binding targets. Examples include, but are not limited to, innate-immune proteins (e.g., without limitations, MBL, Dectin-1, TLR2, and TLR4 and any proteins disclosed in U.S. Provisional Application No. 61/508,957, the content of which is incorporated herein by reference in its entirety) and proteins comprising the chitin-binding domain. Such innate-immune proteins and chitin-binding domain proteins can be used to detect their corresponding pattern-recognition targets (e.g., microbes such as bacteria) and fungus, respectively. By way of example only, instead of using pathogen-specific antibodies as probe reagents in the detection reagents as shown in  FIG.  1   , innate-immune proteins (e.g., MBL) or chitin-binding domain proteins can be used as probe reagents for detection of pathogens. While such detection reagents can be used to detect pathogens, they may not be pathogen-specific, as compared to the ones using pathogen-specific antibodies as probes molecules. 
     In some embodiments, the probe reagent can be an aptamer. In some embodiments, the probe reagent can be a DNA or RNA aptamer. The aptamers can be used in various bioassays, e.g., in the same way as antibodies or nucleic acids described herein. By way of example only,  FIG.  2    shows some exemplary embodiments of the detection reagents comprising at least one (e.g., 1, 2, 3, 4, 5 or more) DNA aptamers (e.g., with a nucleotide sequence complementary to nuclear reprogramming factors, such as Oct4, Sox2, and Klf4). Such detection reagents can be used to determine RNA expression level of nuclear reprogramming factors in somatic cells for detecting, screening, or identifying stem cells (e.g., induced pluripotency stem cells). 
     In some embodiments, the probe reagent can be a cell surface receptor ligand. As used herein, a “cell surface receptor ligand” refers to a molecule that can bind to the outer surface of a cell. Exemplary, cell surface receptor ligand includes, for example, a cell surface receptor binding peptide, a cell surface receptor binding glycopeptide, a cell surface receptor binding protein, a cell surface receptor binding glycoprotein, a cell surface receptor binding organic compound, and a cell surface receptor binding drug. Additional cell surface receptor ligands include, but are not limited to, cytokines, growth factors, hormones, antibodies, and angiogenic factors. 
     When the detection reagents described herein are used as targeted delivery vehicles, e.g., for a diagnostic agent, in some embodiments, the probe reagent can be an endosomolytic ligand. As used herein, the term “endosomolytic ligand” refers to molecules having endosomolytic properties. Endosomolytic ligands can promote the lysis of and/or transport of the composition described herein, or its components, from the cellular compartments such as the endosome, lysosome, endoplasmic reticulum (ER), Golgi apparatus, microtubule, peroxisome, or other vesicular bodies within the cell, to the cytoplasm of the cell. Some exemplary endosomolytic ligands include, but are not limited to, imidazoles, poly or oligoimidazoles, linear or branched polyethyleneimines (PEIs), linear and branched polyamines, e.g. spermine, cationic linear and branched polyamines, polycarboxylates, polycations, masked oligo or poly cations or anions, acetals, polyacetals, ketals/polyketals, orthoesters, linear or branched polymers with masked or unmasked cationic or anionic charges, dendrimers with masked or unmasked cationic or anionic charges, polyanionic peptides, polyanionic peptidomimetics, pH-sensitive peptides, natural and synthetic fusogenic lipids, natural and synthetic cationic lipids. 
     In other embodiments, the probe reagent for use in delivery of an agent (e.g., a diagnostic agent) encapsulated within the detection reagents described herein can be a PK modulating ligand. As used herein, the terms “PK modulating ligand” and “PK modulator” refers to molecules which can modulate the pharmacokinetics of the composition described herein. Some exemplary PK modulator include, but are not limited to, lipophilic molecules, bile acids, sterols, phospholipid analogues, peptides, protein binding agents, vitamins, fatty acids, phenoxazine, aspirin, naproxen, ibuprofen, suprofen, ketoprofen, (S)-(+)-pranoprofen, carprofen, PEGs, biotin, and transthyretia-binding ligands (e.g., tetraiidothyroacetic acid, 2, 4, 6-triiodophenol and flufenamic acid). 
     In various embodiments, the detection reagent described herein can comprise one kind/species of probe reagents or different kinds/species of probe reagents. In some embodiments, the kind/species of the probe reagents present in the detection reagent can be the same. In other embodiments, the detection reagent can include at least one different kind/species of the probe reagents (e.g., 1, 2, 3, 4, 5, or 6 probe reagent species). In such embodiments, the distinct probe reagent species can be different from the others by types (e.g., antibodies vs. DNA aptamers), binding domains, and/or target analytes. 
     Nucleic Acid Labels 
     In accordance with embodiments of various aspects described herein, the nucleic acid label or nucleic acid tag comprises at least one pre-determined nucleic acid subsequence, which is used to identify an analyte or target. In some embodiments, the nucleic acid label or nucleic acid tag can comprise any number of the pre-determined nucleic acid subsequences, e.g., ranging from about 1 to about 100, from about 2 to about 80, or from about 3 to about 50. In some embodiments, the nucleic acid label or nucleic acid tag can comprise at least about 1, at least about 2, at least about 3, at least about 4, at least about 5, at least about 6, at least about 7, at least about 8, at least about 9, at least about 10, at least about 15, at least about 20, at least about 30, at least about 40, at least about 50, at least about 60, at least about 70 or more pre-determined nucleic acid subsequences. In some embodiments, the nucleic acid label or nucleic acid tag can comprise 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 30, 40, 50, 60, 70 or more pre-determined nucleic acid subsequences. Without wishing to be bound, the minimum number of pre-determined nucleic acid subsequences (n) required in the detection reagent can vary upon the number of distinct probes to be detected (X) and/or the number of distinct detectable labels (e.g., optical labels such as fluorescent labels or quantum dots) available to be used (Y), and n can be determined by the equation: where the mathematical function “ceiling” refers to rounding up a non-integer number to the nearest integer, when needed. For example, if 4 distinct detectable labels (Y) are used to distinguish 62 distinct probe reagents (X), n=ceiling (2.98) ˜0.3. Therefore, at least three pre-determined nucleic acid subsequences are required in this example. 
     In some embodiments where the detectable labels include no-color (dark), the number of distinct detectable label available to be used can become Y+1. In such embodiments, n can be determined by the equation: and thus fewer pre-determined nucleic acid subsequences can be used. However, the combination in which all readout cycles are dark should not be allowed. 
     Further, the pre-determined nucleic acid subsequences can be designed such that each readout cycle can light up in multiple colors. Thus, 2 Y  instead of Y is used in the equation for n above and fewer pre-determined nucleic acid subsequences can thus be required. However, the combination in which all readout cycles are dark should not be allowed. 
     Additionally, while colors are generally used in a binary fashion, i.e., whether the color is present or not, in the above examples, the color intensity can also be used as a parameter of a signal signature. For example, if one detectable label is allowed to light up twice as brightly in a different color than another, the multiplexing capacity can be even further expanded. 
     The pre-determined nucleic acid subsequences can be constructed from any types of nucleic acids, including, but not limited to, DNA, RNA, PNA, LNA and any combinations thereof. 
     Each of the pre-determined subsequences of the nucleic acid label can be independently of any length. In certain embodiments, the pre-determined subsequences can each independently comprise a length of about 1 nucleobase to about 100 nucleobases, from about 1 nucleobase to about 50 nucleobases, from about 2 nucleobases to about 50 nucleobases, from about 5 nucleobases to about 30 nucleobases, or from about 5 nucleobases to about 20 nucleobases. In some embodiments, the pre-determined subsequences can each independently comprise one or more nucleobases, e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more nucleobases. 
     The achievable length of the pre-determined subsequences can affect the degree of multiplexibility. In some embodiments, the achievable length of the pre-determined subsequences can be a function of the decreasing fluorescence intensity over many cycles of stripped and rehybridization (i.e. diffusion of the sequenceable particles, degradation, increasing background noise). In the case of DNA or RNA based nucleic acid labels that are amplified in situ, modified base is incorporated during its synthesis (i.e., dUTP, biotin, Acrydite, aminoallele), enabling these detection reagents to be permanently embedded in a film (regardless of the film thickness) of functionalized polyacrylamide (i.e. Acrydite streptavidin, NHS ester Acrydite). The embedded material can then be stripped and rehybridized for many more cycles without altering its spatial architecture and minimizing the background noise. 
     Two or more pre-determined subsequences can be conjugated together within a nucleic acid label using any methods known in the art. In some embodiments, two or more pre-determined subsequences can be conjugated together by a sequence linker. The term “sequence linker” as used herein generally refers to an entity that connects two sequences or subsequences as described herein together. 
     In some embodiments, the sequence linker can be a direct bond or an atom such as nitrogen, oxygen or sulfur; a unit such as NR 1 , C(O), C(O)NH, SO, SO 2 , SO 2 NH; or a chain of atoms. If needed, the two ends of the pre-determined subsequences can be linked together by providing on the two ends of the pre-determined subsequences complementary chemical functionalities that undergo a coupling reaction. In particular embodiments, the sequence linker is a direct bond, including, but not limited to, a phosphodiester bond. For example, a 3′ carbon atom of a sugar base at the 5′ end nucleotide of a first pre-determined subsequence can interact with the 5′ carbon atom of another sugar base at the 3′ end nucleotide of a second pre-determined subsequence to form a covalent bond, e.g., a phosphodiester bond. As such, two or more pre-determined subsequences can be bonded together to form a longer and contiguous pre-determined subsequence. 
     In some embodiments, the sequence linker can be a nucleotidic linker. The term “nucleotidic linker” as used herein refers to a linker of one nucleotide long or a sequence substantially comprising a plurality of nucleotides. In some embodiments, the nucleotidic linker can have a sequence length of at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, at least 15, at least 20, at least 30 or more nucleotides. The sequence length of the nucleotidic linker can vary with a number of factors, e.g., detection methods, and/or properties of optical labels. Without wishing to be bound by theory, in some embodiments, increasing the length of the nucleotidic linker can increase the flexibility of the nucleic acid label, e.g., to increase the binding frequency between a pre-determined sequence and a decoder probe, the term of which will be discussed later. However, too long a nucleotidic linker can result in a too long nucleic acid label, which could overlap with other nucleic acid labels of the detection reagents during an assay and thus reduce the quality and/or accuracy of the signal detection. One of skill in the art can determine the optimum length of the nucleotidic linker without undue experimentations. 
     The nucleotidic linker can be in any structure or conformation. In some embodiments, the nucleotidic linker can be in a structure selected from the group consisting of single-stranded, double-stranded, partially double-stranded, a hairpin, or any combinations thereof. 
     In some embodiments, the sequence linker can be a bead or a nanoparticle acting as a hub. Accordingly, two or more pre-determined subsequences can be independently conjugated together via a bead or a nanoparticle. 
     Without wishing to be bound, while the sequence linker can be a direct bond, an atom, a nucleotidic linker, or any combinations thereof, the sequence linker can also include a sequence of amino acids, a polymer chain, a microbead, a nanobead, or any combinations thereof. To provide for the linkages between sequence linker, in some embodiments, different functionalities can be introduced to the ends of sequence linker and/or the pre-determined subsequences. Examples of functionalities include, but are not limited to, amide groups, including carbonic acid derivatives, ethers, esters, including organic and inorganic esters, amino, urethane, urea and any combinations thereof. 
     In some embodiments, the nucleic acid label is substantially a polynucleotide sequence containing one or more pre-determined subsequences. In such embodiments, any two pre-determined subsequences are either joined or conjugated together by a direct bond such as a phosphodiester bond (to produce longer contiguous subsequence), a nucleotidic linker of any desirable length, or any combinations thereof. 
     In such embodiments, the nucleic acid label of the detection reagent can be adapted to any configuration or structure. In some embodiments, the nucleic acid label can be single-stranded, double-stranded, partially double-stranded, a hairpin, linear, circular, branched, a concatemer, or any combinations thereof. In some embodiments, the nucleic acid label can be a linear polynucleotide sequence. 
     In some embodiments, the nucleic acid label can be a circular polynucleotide sequence. The advantage of using a circular nucleic acid label is that it can be amplified using rolling-circle amplification or hyperbranched rolling-circle amplification to generate a long continuous nucleic acid molecule that contains multiple copies of the same nucleic acid label sequences linked in series (also known as concatemer), thus resulting in an amplified signal. In some embodiments, instead of pre-forming the detection reagents comprising the circular nucleic acid label(s) and the probe reagent(s), detection reagents comprising linear polynucleotide(s) and the probe reagent(s) can be first synthesized. The circular nucleic acid labels can then added to hybridize with the linear polynucleotide(s) before or after the probe reagent(s) bind to the analytes. In such embodiments, while requiring an extra step, this approach can have the advantage over direct attachment of circular nucleic acid labels in that it does not require chemical modification of the nucleic acid label for conjugation with the probe reagents, thus resulting in a circular nucleic acid label that is compatible with a broader range of amplification enzymes. Furthermore, the linear polynucleotides can be smaller than the secondary circular nucleic acid labels, facilitating diffusion of the probe reagents (and the detection reagents) to their targets. In other embodiments, the linear polynucleotides can be circularized using a suitable double-stranded or single-stranded ligase, with or without the addition of a suitable ligation template. Without wishing to be bound by theory, such embodiments can avoid the extra hybridization that is required when a pre-circularized oligonucleotide is used instead. 
     When the detection reagents described herein are used as FISH probes, the nucleic acid labels and the FISH probes can be part of the same nucleic acid sequence construct, and thus the circularization can encompass the entire construct (e.g., both the nucleic acid labels and FISH probes). A schematic representation of exemplary FISH probes for SeqTagged FISH is shown in  FIG.  13   . 
     In some embodiments, the method described herein can be used to identify a class an analyte, e.g., a pathogen belongs to. For example, the method can be used to identify if a pathogen is a Gram-negative, Gram-positive, or some other class of pathogen, e.g., yeast. Thus, the method described herein can be used to as Gram test to determine whether a suspected pathogen is Gram positive, Gram negative or yeast. This can be useful for quickly identifying the type of infection in a subject and administering appropriate therapy. By way of example only, this can be accomplished using a detection reagent comprising a class-specific probe, also referred to as “Gram-stain like probe” herein. Again by way of example only, the probe can be a DNA probe for FISH. 
     In some embodiment, the FISH probe for identifying eubacteria can comprise the nucleotide sequence of SEQ ID NO: 4 (GCTGCCTCCCGTAGGAGT). An exemplary SeqTag labeled FISH-probe for identifying eubacteria can comprise the nucleotide sequence of SEQ ID NO: 5 (CTGCCTCCCGTAGGAGTTTTTTCGCTTTAGCCTAAGTGAAATC). 
     In some embodiments, the FISH probe for identifying yeast can comprise the nucleotide sequence of SEQ ID NO: 6 (CTCTGGCTTCACCCTATTC. An exemplary SeqTag labeled FISH-probe for identifying yeast can comprise the nucleotide sequence of SEQ ID NO: 7 (CTCTGGCTTCACCCTATTCTTTTTCGCTTTTTTGGGGAAAAGACA). 
     In some embodiments, the FISH probe for identifying firmicutes can comprise the nucleotide sequence of SEQ ID NO: 8 (CGGAAGATTCCCTACTGC). An exemplary SeqTag labeled FISH-probe for identifying yeast can comprise the nucleotide sequence of SEQ ID NO: 9 (CGGAAGATTCCCTACTGCTTTTTCGCTTTCTGTAATGGAGTGGA). 
     In the SeqTag labeled FISH probes discussed above, each probe can be assigned a particular “signal signature” for each of the three readout steps. For example, colors can be labeled at B, C, and D. In some embodiments, each color can be from a different fluorophore, such as FAM, Cy3 and Cy5. Each signal signature can take advantage of multiple fluorophores simultaneously or even the same fluorophore multiple times, e.g., a SeqTag with signal signature corresponding to “DDDC.” 
     An exemplary signal signature for identifying eubacteria, yeast or firmicutes is shown in Table 1. As shown, each class has a different assigned code for the first readout step. For example, for the first readout, eubacteria are assigned color C′ yeast color D and firmicutes color B. On readout, eubacteria will show up as color C, yeast as color D, firmicutes as both colors B and C. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                 Assigned code 
                 Effective code 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Name 
                 S1 
                 S2 
                 S3 
                 S1 
                 S2 
                 S3 
               
               
                   
               
            
           
           
               
               
               
            
               
                   Eubacteria -Kempf 
                 C 
                 C 
               
               
                 All_yeast-Kempf 
                 D 
                 D 
               
               
                   Firmicutes -pB-00196 
                 B 
                 BC 
               
               
                   
               
            
           
         
       
     
     After identifying the class of pathogens, the pathogens can be further probed for identifying the specific pathogen or genus using the method described herein. For example, the detection reagent can comprise a pathogen specific probe that binds to a specific pathogen or genus of pathogens. For example, the probe can be a FISH probe that specifically binds to a specific pathogen. Some exemplary pathogen specific FISH probes are shown in Table 2. 
     
       
         
           
               
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Name 
                   
               
            
           
           
               
               
               
               
               
            
               
                 SEQ ID 
                   
                   
                 Assigned  
                 Effective  
               
               
                 NO: 
                   
                 probeBase FISH Sequence 
                 code 
                 code 
               
               
                   
               
            
           
           
               
               
            
               
                   
                 Gram+ 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 10 
                 Staph_spp-Kempf 
                 TCCTCCATATCTCTGCGC 
                 DD 
                 B 
                 BC 
                 DD 
                 B 
               
               
                   
               
               
                 11 
                 S_Aureus-Kempf 
                 GAAGCAAGCTTCTCGTCCG 
                 CD 
                 B 
                 BC 
                 CDDD 
                 BB 
               
               
                   
               
               
                 12 
                 Streptococcus_spp- 
                 CACTCTCCCCTTCTGCAC 
                 DD 
                 D 
                 BC 
                 DD 
                 D 
               
               
                   
                 Kempf 
                   
                   
                   
                   
                   
                   
               
               
                   
               
               
                 13 
                 S_Pneumoniae- 
                 GTGATGCAAGTGCACCTT 
                 B 
                 DC 
                 BC 
                 DDB 
                 DDC 
               
               
                   
                 Kempf 
                   
                   
                   
                   
                   
                   
               
               
                   
               
               
                 14 
                 S_Pyogenes- 
                 TTCCAAAGCGTACATTGGTT 
                 C 
                 DB 
                 BC 
                 DDC 
                 DDB 
               
               
                   
                 Kempf 
                   
                   
                   
                   
                   
                   
               
               
                   
               
               
                 15 
                 S_Agalactiae- 
                 GTAAACACCAAACMTCAGCG 
                 D 
                 DC 
                 BC 
                 DDD 
                 DDC 
               
               
                   
                 Kempf 
                   
                   
                   
                   
                   
                   
               
               
                   
               
               
                 16 
                 B_subtilis-pB- 
                 CGA AGG GGA CGT CCT ATC 
                 C 
                 DD 
                 BC 
                 C 
                 DD 
               
               
                   
                 00401 
                 T 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 17 
                 L_acidophilus-pB- 
                 CAG GCT TGC TCC TCG TTG 
                 DD 
                 C 
                 BC 
                 DD 
                 C 
               
               
                   
                 00711 
                   
                   
                   
                   
                   
                   
               
               
                   
               
            
           
           
               
               
            
               
                   
                 Gram− 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 18 
                 P_Aeruginosa- 
                 TCTCGGCCTTGAAACCCC 
                 B 
                 B 
                 C 
                 B 
                 B 
               
               
                   
                 Kempf 
                   
                   
                   
                   
                   
                   
               
               
                   
               
               
                 19 
                 K_Pneumoniae- 
                 CCTACACACCAGCGTGCC 
                 B 
                 DD 
                 C 
                 B 
                 DD 
               
               
                   
                 Kempf 
                   
                   
                   
                   
                   
                   
               
               
                   
               
               
                 20 
                 H_influenzae-pB- 
                 CCG CAC TTT CAT CTT CCG 
                 B 
                 BC 
                 C 
                 B 
                 BC 
               
               
                   
                 00348 
                   
                   
                   
                   
                   
                   
               
               
                   
               
               
                 21 
                 B_cepacia-pB- 
                 CTG TGC GCC GGT TCT CTT 
                 DD 
                 B 
                 C 
                 DD 
                 B 
               
               
                   
                 00346 
                   
                   
                   
                   
                   
                   
               
               
                   
               
               
                 22 
                 K_oxytoca-pB- 
                 CTA CAA GAC TCC AGC CTG 
                 DD 
                 C 
                 C 
                 DD 
                 C 
               
               
                   
                 01681 
                 CC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 23 
                 E_coli-pB-02569- 
                 ATG AGC AAA GGT ATT AAC 
                 B 
                 C 
                 C 
                 B 
                 C 
               
               
                   
                 comp1 
                 TTT ACT CCC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 24 
                 Shewanella_spp- 
                 AGC TAA TCC CAC CTA GGT 
                 BC 
                 B 
                 C 
                 BC 
                 B 
               
               
                   
                 pB-01191-mod 
                 TCA TC 
                   
                   
                   
                   
                   
               
               
                   
               
               
                 25 
                 H_pylori-pB-00361 
                 CACACCTGACTGACTATCCCG 
                 C 
                 B 
                 C 
                 C 
                 B 
               
               
                   
               
            
           
           
               
               
            
               
                   
                 Yeast 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 26 
                 C_Albicans-Kempf 
                 GCCAAGGCTTATACTCGCT 
                 C 
                 BC 
                 D 
                 C 
                 BC 
               
               
                   
               
               
                 27 
                 C_Glabrata_Kempf 
                 CCGCCAAGCCACAAGGACT 
                 C 
                 CD 
                 D 
                 C 
                 CD 
               
               
                   
               
               
                 28 
                 C_Krusei-Kempf 
                 GATTCTCGGCCCCATGGG 
                 BC 
                 C 
                 D 
                 BC 
                 C 
               
               
                   
               
               
                 29 
                 C_Parapsilosis- 
                 CCTGGTTCGCCAAAAAGGC 
                 CD 
                 C 
                 D 
                 CD 
                 C 
               
               
                   
                 Kempf 
               
               
                   
               
            
           
         
       
     
     Exemplary SeqTag labeled FISH-probe for identifying a specific pathogen are shown in Table 3. As shown in Table 3, each specific pathogen can be assigned a specific signal signature based on an assigned color for each readout step and identity of a pathogen can be decoded using this table when the method is carried out using this set of assigned coding. 
     
       
         
           
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                 SEQ ID 
                   
                   
               
               
                 NO: 
                 Name 
                 SeqTag-labeled FISH-probe Sequence 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                   
                 Gram+ 
               
            
           
           
               
               
               
            
               
                 30 
                 Staph_spp-Kempf 
                 TCCTCCATATCTCTGCGCTTTTTCGCTTTCTGGAGAAAGGGCCATTT 
               
               
                   
                   
                 TTCGCTTTCGGTTCCAAAGACACTTTTTCGCTTTCTGGAGAAAGGGC 
               
               
                   
                   
                 CA 
               
               
                   
               
               
                 31 
                 S_Aureus -Kempf 
                 GAAGCAAGCTTCTCGTCCGTTTTTCGCTTTCTGGAGAAAGGGCCATT 
               
               
                   
                   
                 TTTCGCTTTCGGTTCCAAAGACACTTTTTCGCTTTGGAAGCACCTAT 
               
               
                   
                   
                 TCC 
               
               
                   
               
               
                 32 
                 Streptococcus_spp- 
                 CACTCTCCCCTTCTGCACTTTTTCGCTTTCTGGAGAAAGGGCCATTT 
               
               
                   
                 Kempf 
                 TTCGCTTTTCACGATCCCATGTATTTTTCGCTTTCTGGAGAAAGGGC 
               
               
                   
                   
                 CA 
               
               
                   
               
               
                 33 
                 S_Pneumoniae-Kempf 
                 GTGATGCAAGTGCACCTTTTTTTCGCTTTGAAGCCGGTTATAGCTTT 
               
               
                   
                   
                 TTCGCTTTTAGGCATTAGCATTGTTTTTCGCTTTTCACGATCCCATG 
               
               
                   
                   
                 TA 
               
               
                   
               
               
                 34 
                 S_Pyogenes-Kempf 
                 TTCCAAAGCGTACATTGGTTTTTTTCGCTTTCGGTTCCAAAGACACT 
               
               
                   
                   
                 TTTTCGCTTTGGAAGCACCTATTCCTTTTTCGCTTTTCACGATCCCA 
               
               
                   
                   
                 TGTA 
               
               
                   
               
               
                 35 
                 S_Agalactiae-Kempf 
                 GTAAACACCAAACMTCAGCGTTTTTCGCTTTGAAGCCGGTTATAGCT 
               
               
                   
                   
                 TTTTCGCTTTCTGGAGAAAGGGCCATTTTTCGCTTTTCACGATCCCA 
               
               
                   
                   
                 TGTA 
               
               
                   
               
               
                 36 
                 B_subtilis-pB-00401 
                 CGA AGG GGA CGT CCT ATC TTTTTTCGCTTTTCACGATCCCA 
               
               
                   
                   
                 TGTATTTTTCGCTTTGGAAGCACCTATTCCTTTTTCGCTTTTCACGA 
               
               
                   
                   
                 TCCCATGTA 
               
               
                   
               
               
                 37 
                 L_acidophilus-pB- 
                 CAG GCT TGC TCC TCG TTGTTTTTCGCTTTCTGGAGAAAGGGC 
               
               
                   
                 00711 
                 CATTTTTCGCTTTGAAGCCGGTTATAGCTTTTTCGCTTTCTGGAGAA 
               
               
                   
                   
                 AGGGCCA 
               
               
                   
               
            
           
           
               
               
            
               
                   
                 Gram− 
               
            
           
           
               
               
               
            
               
                 38 
                 P_Aeruginosa-Kempf 
                 TCTCGGCCTTGAAACCCCTTTTTCGCTTTTAGGCATTAGCATTGTTT 
               
               
                   
                   
                 TTCGCTTTCGGTTCCAAAGACAC 
               
               
                   
               
               
                 39 
                 K_Pneumoniae-Kempf 
                 CCTACACACCAGCGTGCCTTTTTCGCTTTTCACGATCCCATGTATTT 
               
               
                   
                   
                 TTCGCTTTTAGGCATTAGCATTGTTTTTCGCTTTTCACGATCCCATG 
               
               
                   
                   
                 TA 
               
               
                   
               
               
                 40 
                 H_influenzae-pB - 
                 CCG CAC TTT CAT CTT CCGTTTTTCGCTTTCGGTTCCAAAGAC 
               
               
                   
                 00348 
                 ACTTTTTCGCTTTTAGGCATTAGCATTGTTTTTCGCTTTGAAGCCGG 
               
               
                   
                   
                 TTATAGC 
               
               
                   
               
               
                 41 
                 B_cepacia-pB-00346 
                 CTG TGC GCC GGT TCT CTTTTTTTCGCTTTCTGGAGAAAGGGC 
               
               
                   
                   
                 CATTTTTCGCTTTCGGTTCCAAAGACACTTTTTCGCTTTCTGGAGAA 
               
               
                   
                   
                 AGGGCCA 
               
               
                   
               
               
                 42 
                 K_oxytoca-pB-01681 
                 CTA CAA GAC TCC AGC CTG CCTTTTTCGCTTTCTGGAGAAAG 
               
               
                   
                   
                 GGCCATTTTTCGCTTTGAAGCCGGTTATAGCTTTTTCGCTTTCTGGA 
               
               
                   
                   
                 GAAAGGGCCA 
               
               
                   
               
               
                 43 
                 E_coli-pB-02569- 
                 ATG AGC AAA GGT ATT AAC TTT ACT CCCTTTTTCGCTTTT 
               
               
                   
                 comp1 
                 AGGCATTAGCATTGTTTTTCGCTTTGAAGCCGGTTATAGC 
               
               
                   
               
               
                 44 
                 Shewanella_spp-pB- 
                 AGC TAA TCC CAC CTA GGT TCA TCTTTTTCGCTTTTAGGCA 
               
               
                   
                 01191-mod 
                 TTAGCATTGTTTTTCGCTTTCGGTTCCAAAGACACTTTTTCGCTTTG 
               
               
                   
                   
                 GAAGCACCTATTCC 
               
               
                   
               
               
                 45 
                 H_pylori-pB-00361 
                 CACACCTGACTGACTATCCCGTTTTTCGCTTTGGAAGCACCTATTCC 
               
               
                   
                   
                 TTTTTCGCTTTCGGTTCCAAAGACAC 
               
               
                   
               
            
           
           
               
               
            
               
                   
                 Yeast 
               
            
           
           
               
               
               
            
               
                 46 
                 C_Albicans-Kempf 
                 GCCAAGGCTTATACTCGCTTTTTTCGCTTTCGGTTCCAAAGACACTT 
               
               
                   
                   
                 TTTCGCTTTGGAAGCACCTATTCCTTTTTCGCTTTGAAGCCGGTTAT 
               
               
                   
                   
                 AGC 
               
               
                   
               
               
                 47 
                 C_Glabrata_Kempf 
                 CCGCCAAGCCACAAGGACTTTTTTCGCTTTGAAGCCGGTTATAGCTT 
               
               
                   
                   
                 TTTCGCTTTGGAAGCACCTATTCCTTTTTCGCTTTTCACGATCCCAT 
               
               
                   
                   
                 GTA 
               
               
                   
               
               
                 48 
                 C_Krusei-Kempf 
                 GATTCTCGGCCCCATGGGTTTTTCGCTTTTAGGCATTAGCATTGTTT 
               
               
                   
                   
                 TTCGCTTTGAAGCCGGTTATAGCTTTTTCGCTTTGGAAGCACCTATT 
               
               
                   
                   
                 CC 
               
               
                   
               
               
                 49 
                 C_Parapsilosis- 
                 CCTGGTTCGCCAAAAAGGCTTTTTCGCTTTCTGGAGAAAGGGCCATT 
               
               
                   
                 Kempf 
                 TTTCGCTTTGAAGCCGGTTATAGCTTTTTCGCTTTGGAAGCACCTAT 
               
               
                   
                   
                 TCC 
               
               
                   
               
            
           
         
       
     
     As shown in Table 3, the “signal signature” can comprise multiple fluorescence “colors” in each step. For example,  E. coli  can be marked as red in step 1 and red+green in step 2 and blue in step 3. The “signal signature” can also be encoded in the brightness of the color at each step. For example,  E. coli  could be marked as red in step 1 and 3 times brighter red in step 2. 
     Exemplary hybridization sites for generating the different signal signatures at different steps using the exemplary SeqTag labeled FISH-probes described above are shown in Table 4. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                 SEQ ID 
                 Assigned 
                   
               
               
                   
                 NO: 
                 “Color” 
               
               
                   
                   
               
             
            
               
                   
                   
                   
                 Set 1 
               
               
                   
                 50 
                 B 
                 CGCTTTCTGTAATGGAGTGGA 
               
               
                   
                   
               
               
                   
                 51 
                 C 
                 CGCTTTAGCCTAAGTGAAATC 
               
               
                   
                   
               
               
                   
                 52 
                 D 
                 CGCTTTTTTGGGGAAAAGACA 
               
               
                   
                   
               
               
                   
                   
                   
                 Set 2 
               
               
                   
                 53 
                 B 
                 CGCTTTTAGGCATTAGCATTG 
               
               
                   
                   
               
               
                   
                 54 
                 C 
                 CGCTTTGGAAGCACCTATTCC 
               
               
                   
                   
               
               
                   
                 55 
                 D 
                 CGCTTTCTGGAGAAAGGGCCA 
               
               
                   
                   
               
               
                   
                   
                   
                 Set 3 
               
               
                   
                 56 
                 B 
                 CGCTTTCGGTTCCAAAGACAC 
               
               
                   
                   
               
               
                   
                 57 
                 C 
                 CGCTTTGAAGCCGGTTATAGC 
               
               
                   
                   
               
               
                   
                 58 
                 D 
                 CGCTTTTCACGATCCCATGTA 
               
               
                   
                   
               
            
           
         
       
     
     In some embodiments, multiple detection reagents can be used to identify a specific analyte. For example, a first set of probes can be used to identify whether the potential pathogen is gram-position, gram-negative and then another set of probes to identify it more specifically. Both probes would need to produce a detectable signal, allowing one to use, for example, Table 3 to uniquely identify the pathogen. 
     In some embodiments, the nucleic acid label can be a concatemer, including a rolony or a DNA nanoball that is large enough to act as a particle rather than simply a strand of nucleic acid. Using a concatemer as a nucleic acid label can eliminate the need for in-situ enzymatic treatment of circular nucleic acid amplification, but it can also increase the overall molecular weight of the detection reagent and thus retard diffusion. Similar to the circular nucleic acid labels as described above, an exemplary approach of hybridizing concatemers with the linear polypeptides of the detection reagents after probe reagents bind to the analytes can be used to facilitate diffusion of the probe reagents (and the detection reagents) to their targets. 
     To increase the accuracy and/or specificity of the methods described herein, in various embodiments, the nucleic acid label can be designed for minimal cross-hybridization of bases with each other. Various art-recognized computational programs or algorithms are available to design nucleic acid sequences with minimal cross-hybridization. Thus, one of skill in the art can optimize the nucleic acid label sequence using any methods or algorithms known in the art. 
     In some embodiments, the nucleic acid labels described herein can be synthetic nucleic acid molecules (e.g., DNA, RNA, or DNA/RNA hybrids), and can be rationally-designed to have features that optimize labeling and detection of the detection reagents, and that prevent secondary structure formation. In some embodiments, a nucleic acid label is a designed polynucleotide sequence from about 50 to 50,000 bases long. 
     In some embodiments, the nucleic acid labels described herein can be designed to minimize predictable secondary structures, and/or be designed such that each nucleic acid label can hybridize only against its own target. In some embodiments, the nucleic acid labels described herein can be designed to be devoid of any secondary structure. Putative secondary structures (e.g. hairpins, folding, or internal base pairing) can be predicted by methods known in the art such as MFOLD. Without intending to be limited to any theory, in some embodiments, predictable secondary structure in the nucleic acid label can be minimized by avoiding inverted repeats and by skewing the backbone-specific content such that the backbone of the nucleic acid label is CT or GA-rich. Any art-recognized methods, e.g., MFOLD, can be used to verify if each nucleic acid label can hybridize only against its own target. 
     Sequences can also be screened to avoid common six-base-cutter restriction enzyme recognition sites. Selected sequences can be additionally subjected to predicted secondary structure analysis, and those with the least secondary structure may be chosen for further evaluation. Any program known in the art can be used to predict secondary structure, such as the MFOLD program (Zuker, 2003, Nucleic Acids Res. 31 (13):3406-15; Mathews et al., 1999, J. Mol. Biol. 288:911-940). 
     In some embodiments, the nucleic acid label can comprise only a subset of the A, G, C, T (and/or U) nucleotides or modified nucleotides thereof. In some embodiments, the nucleic acid label can comprise only one of the A, G, C, T (and/or U) nucleotides or modified nucleotides thereof. In some embodiments, the nucleic acid can comprise two of the A, C, T (and/or U) nucleotides or modified nucleotides thereof. In some embodiments, the nucleic acid label can comprise only three of the A, G, C, and T (and/or U) nucleotides or modified nucleotides thereof. In some embodiments, the nucleic acid label can comprise only four of the A, G, C, and T (and/or U) nucleotides or modified nucleotides thereof. The subset of the A, G, C and T (and/or U) nucleotides or modified nucleotide thereof can be selected from the group consisting of A; G; C; T; U; (A,G); (A,C); (G,T); (G,U); (C,T); (C,U); (G,T,U); (C,T,U); (A,C,G); (A,G,T); (A,G,U); (A,C,T); (A,C,U); (C,G,T); (C,G,U); (A,C,T,U); and (C,G,T,U). 
     Without wishing to be bound, the nucleic acid label can be a modified nucleic acid label. An exemplary modification of the nucleic acid label includes, without limitations, attaching one or more detectable molecules to the nucleic acid label (either to one end of or along the nucleic acid label sequence). The detectable molecule can be any optical molecule, including, but not limited to, a small-molecule dye, a fluorescent protein, a quantum dot, or any combinations thereof. In another embodiment, at least one end of the nucleic acid label can be modified to include a chemical functional group and/or a protein or peptide to facilitate the conjugation between the nucleic acid label and the probe reagent. 
     In some embodiments, at least one (including, e.g., at least two, at least three, at least four, at least five, at least six or more) nucleic acids or nucleotides present in the nucleic acid label can be modified. For example, the nucleic acid can comprise one or more nucleic acid modifications as described herein, e.g., selected from the group consisting of internucleotide linkage modifications (intersugar linkage modifications), sugar modifications, nucleobase modifications, backbone modifications/replacements, and any combinations thereof. 
     Conjugation Between a Nucleic Acid Label and a Probe Reagent 
     In accordance with embodiments of various aspects described herein, the detection reagent comprises at least one probe reagent and at least one nucleic acid label, wherein the probe reagent and the nucleic acid label can be conjugated together by any methods known in the art. 
     In some embodiments, the probe reagent and the nucleic acid label can be attached or conjugated together by a linker. As used herein, the term “linker” generally refers to an entity that connects the probe reagent and the nucleic acid label together. The linker can be monovalent or multivalent. The term “monovalent” as used herein refers to the capacity of a linker to join one probe reagent to one nucleic acid label. The term “multivalent” as used herein refers to the capacity of a linker to bind with one or more probe reagents and/or nucleic acid labels. In some embodiments, a multivalent linker can join at least one probe reagent to a plurality of nucleic acid labels (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10 or more nucleic acid labels). 
     In some embodiments, the term “linker” means an organic moiety that connects two parts of a compound. Such linkers typically comprise a direct bond or an atom such as oxygen or sulfur, a unit such as NH, C(O), C(O)NH, SO, SO 2 , SO 2 NH, SS, or a chain of atoms, such as substituted or unsubstituted C 1 -C 6  alkyl, substituted or unsubstituted C 2 -C 6  alkenyl, substituted or unsubstituted C 2 -C 6  alkynyl, substituted or unsubstituted C 6 -C 12  aryl, substituted or unsubstituted C 5 -C 12  heteroaryl, substituted or unsubstituted C 5 -C 12  heterocyclyl, substituted or unsubstituted C 3 -C 12  cycloalkyl, where one or more methylenes can be interrupted or terminated by O, S, S(O), SO 2 , NH, C(O). 
     In some embodiments, the linker is a branched linker. The branchpoint of the branched linker may be at least trivalent, but can be a tetravalent, pentavalent or hexavalent atom, or a group presenting such multiple valencies. In some embodiments, the branchpoint is —N, —N(R)—C, —O—C, —S—C, —SS—C, —C(O)N(R)—C, —OC(O)N(R)—C, —N(R)C(O)—C, or —N(R)C(O)O—C; wherein R is independently for each occurrence H or optionally substituted alkyl. In some embodiments, the branchpoint is glycerol or derivative thereof. 
     In some embodiments, linker comprises a cleavable linking group. As used herein, a “cleavable linking group” is a chemical moiety which is sufficiently stable outside the cell, but which upon entry into a target cell is cleaved to release the two parts the linker is holding together. In a preferred embodiment, the cleavable linking group is cleaved at least 10 times or more, preferably at least 100 times faster in the target cell or under a first reference condition (which can, e.g., be selected to mimic or represent intracellular conditions) than in the blood or serum of a subject, or under a second reference condition (which can, e.g., be selected to mimic or represent conditions found in the blood or serum). 
     Cleavable linking groups are susceptible to cleavage agents, e.g., pH, redox potential or the presence of degradative molecules. Generally, cleavage agents are more prevalent or found at higher levels or activities inside cells than in serum or blood. Examples of such degradative agents include: redox agents which are selected for particular substrates or which have no substrate specificity, including, e.g., oxidative or reductive enzymes or reductive agents such as mercaptans, present in cells, that can degrade a redox cleavable linking group by reduction; esterases; amidases; endosomes or agents that can create an acidic environment, e.g., those that result in a pH of five or lower; enzymes that can hydrolyze or degrade an acid cleavable linking group by acting as a general acid, peptidases (which can be substrate specific) and proteases, and phosphatases. 
     A linker can include a cleavable linking group that is cleavable by a particular enzyme. The type of cleavable linking group incorporated into a linker can depend on the cell to be targeted. For example, for liver targeting, cleavable linking groups can include an ester group. Liver cells are rich in esterases, and therefore the linker will be cleaved more efficiently in liver cells than in cell types that are not esterase-rich. Other cell-types rich in esterases include cells of the lung, renal cortex, and testis. 
     Linkers that contain peptide bonds can be used when targeting cell types rich in peptidases, such as liver cells and synoviocytes. 
     In some embodiments, cleavable linking group is cleaved at least 1.25, 1.5, 1.75, 2, 3, 4, 5, 10, 25, 50, or 100 times faster in the cell (or under in vitro conditions selected to mimic intracellular conditions) as compared to blood or serum (or under in vitro conditions selected to mimic extracellular conditions). In some embodiments, the cleavable linking group is cleaved by less than 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%, 5%, or 1% in the blood (or in vitro conditions selected to mimic extracellular conditions) as compared to in the cell (or under in vitro conditions selected to mimic intracellular conditions). 
     Exemplary cleavable linking groups include, but are not limited to, redox cleavable linking groups (e.g., —S—S— and —C(R) 2 —S—S—, wherein R is H or C 1 -C 6  alkyl and at least one R is C 1 -C 6  alkyl such as CH 3  or CH 2 CH 3 ); phosphate-based cleavable linking groups (e.g., —O—P(O)(OR)—O—, —O—P(S)(OR)—O—, —O—P(S)(SR)—O—, —S—P(O)(OR)—O—, —O—P(O)(OR)—S—, —S—P(O)(OR)—S—, P(S)(ORk)-S—, —S—P(S)(OR)—O—, —O—P(O)(R)—O—, —O—P(S)(R)—O—, —S—P(O)(R)—O—, —S—P(S)(R) S—P(O)(R)—S—, —O—P(S)(R)—S—, —O—P(O)(OH)—O—, —O—P(S)(OH)—O—, —O—P(S)(SH)—O—, —S—P(O)(OH)—O—, —O—P(O)(OH)—S—, —S—P(O)(OH)—S—, —O—P(S)(OH)—S—, —S—P(S)(OH)—O—, —O—P(O)(H)—O—, —O—P(S)(H)—O—, —S—P(O)(H)—O—, —S—P(S)(H)—O—, —S—P(O)(H)—S—, and —O—P(S)(H)—S—, wherein R is optionally substituted linear or branched C 1 -C 10  alkyl); acid celavable linking groups (e.g., hydrazones, esters, and esters of amino acids, —C═NN— and —OC(O)—); ester-based cleavable linking groups (e.g., —C(O)O—); peptide-based cleavable linking groups, (e.g., linking groups that are cleaved by enzymes such as peptidases and proteases in cells, e.g., —NHCHR A C(O)NHCHR B C(O)—, where RA and RB are the R groups of the two adjacent amino acids). A peptide based cleavable linking group comprises two or more amino acids. In some embodiments, the peptide-based cleavage linkage comprises the amino acid sequence that is the substrate for a peptidase or a protease found in cells. 
     In some embodiments, an acid cleavable linking group is cleaveable in an acidic environment with a pH of about 6.5 or lower (e.g., about 6.0, 5.5, 5.0, or lower), or by agents such as enzymes that can act as a general acid. 
     In addition to covalent linkages, two parts of a compound can be linked together by an affinity binding pair. The term “affinity binding pair” or “binding pair” refers to first and second molecules that specifically bind to each other. One member of the binding pair is conjugated with first part to be linked while the second member is conjugated with the second part to be linked. As used herein, the term “specific binding” refers to binding of the first member of the binding pair to the second member of the binding pair with greater affinity and specificity than to other molecules. 
     Exemplary binding pairs include any haptenic or antigenic compound in combination with a corresponding antibody or binding portion or fragment thereof (e.g., digoxigenin and anti-digoxigenin; mouse immunoglobulin and goat antimouse immunoglobulin) and nonimmunological binding pairs (e.g., biotin-avidin, biotin-streptavidin, biotin-neutravidin, hormone [e.g., thyroxine and cortisol-hormone binding protein, receptor-receptor agonist, receptor-receptor antagonist (e.g., acetylcholine receptor-acetylcholine or an analog thereof), IgG-protein A, IgG-protein G, IgG-synthesized protein AG, lectin-carbohydrate, enzyme-enzyme cofactor, enzyme-enzyme inhibitor, and complementary oligonucleotide pairs capable of forming nucleic acid duplexes), and the like. The binding pair can also include a first molecule which is negatively charged and a second molecule which is positively charged. 
     One example of using binding pair conjugation is the biotin-avidin, biotin-streptavidin or biotin-neutravidin conjugation. In this approach, one of the molecule or the peptide is biotinylated and the other is conjugated with avidin or streptavidin. Many commercial kits are also available for biotinylating molecules, such as proteins. 
     Another example of using binding pair conjugation is the biotin-sandwich method. See, e.g., example Davis et al., Proc. Natl. Acad. Sci. USA, 103: 8155-60 (2006). The two molecules to be conjugated together are biotinylated and then conjugated together using at least one tetravalent avidin-like molecule (e.g., avidin, streptavidin, or neutravidin) as a linker. 
     Accordingly, in some embodiments, both the nucleic acid label(s) and probe reagent(s) can be biotinylated and then linked together using an avidin-like molecule (e.g., avidin, streptavidin, or neutravidin). In one embodiment, neutravidin and/or streptavidin is used as a linker to bridge together the biotinylated nucleic acid label(s), e.g., DNA sequence(s), and biotinylated probe reagent(s), e.g., antibody. Without wishing to be bound by theory, each avidin-like molecule (e.g., avidin, streptavidin, or neutravidin) generally has four binding sites, so at most four molecules can be linked together. For example, one biotinylated probe reagent can be linked, via an avidin-like molecule (e.g., avidin, streptavidin or neutravidin), to three biotinylated nucleic acid labels, or in any other combinations (e.g., two biotinylated probe reagents linked to two biotinylated nucleic acid labels). 
     Biotinylation of a nucleic acid label (i.e., attaching a biotin to a nucleic acid label) can occur at any location of the nucleic acid label. In some embodiments, the nucleic acid label can by synthesized or modified with a terminal biotin, i.e., the nucleic acid label can have a biotin at its 5′ end and/or 3′ end. In other embodiments, the nucleic acid label can by synthesized or modified with an internal biotin, i.e., the nucleic acid label can have a biotin anywhere between its 5′ and 3′ ends, but not at its 5′ and/or 3′ ends. Such internal biotinylation can leave at least one end (e.g., both ends) of the nucleic acid label accessible, allowing the nucleic acid label to be circularized after the nucleic acid label has bound, which can in turn, for example, enable rolling circle amplification as described earlier. Chemical modification of the nucleic acid label, e.g., to attach a terminal and/or an internal biotin to the nucleic acid label after synthesis, is within one of skill in the art. 
     For some embodiments where the probe reagent is a nucleic acid, an example of using binding pair conjugation is double-stranded nucleic acid conjugation. In this approach, the first part to be linked is conjugated is with linked a first strand first strand of the double-stranded nucleic acid and the second part to be linked is conjugated with the second strand of the double-stranded nucleic acid. Nucleic acids can include, without limitation, defined sequence segments and sequences comprising nucleotides, ribonucleotides, deoxyribonucleotides, nucleotide analogs, modified nucleotides and nucleotides comprising backbone modifications, branchpoints and nonnucleotide residues, groups or bridges. 
     In some embodiments, the linker can be a linker molecule. Examples of linker molecules can include, but are not limited to, a polymer, sugar, nucleic acid, peptide, protein, hydrocarbon, lipid, polyethelyne glycol, crosslinker, or combination thereof. 
     Non-limiting examples of crosslinkers that can be used as linker molecules can include, but are not limited to, amine-to-amine crosslinkers (e.g., but are not limited to the ones based on NHS-ester and/or imidoester reactive groups), amine-to-sulfhydryl crosslinkers, carboxyl-to-amine crosslinkers (e.g., but are not limited to, carbodiimide crosslinking agents such as DCC, and/or EDC (EDAC); and/or N-hydroxysuccinimide (NHS)), photoreactive crosslinkers (e.g., but not limited to, aryl azide, diazirine and any art-recognized photo-reactive (light-activated) chemical crosslinking reagents), sulfhydryl-to-carbohydrate crosslinkers (e.g., but are not limited to the ones based on malemide and/or hydrazide reactive groups), sulfhydryl-to hydroxyl crosslinkers (e.g., but are not limited to the ones based on maleimide and/or isocyanate reactive groups), sulfhydryl-to-sulfhydryl crosslinkers (e.g., but are not limited to, maleimide and/or pyridyldithiol reactive groups), sulfo-SMCC crosslinkers, sulfo-SBED biotin label transfer reagents, sulfhydryl-based biotin label transfer reagents, photoreactive amino acids (e.g., but are not limited to diazirine analogs of leucine and/or methionine), NHS-azide Staudinger ligation reagents (e.g., but are not limited to, activated azido compounds), NHS-phosphine Staudinger ligation reagents (e.g., but are not limited to, activated phosphine compounds), and any combinations thereof. 
     In some embodiments, any commercially available crosslinkers (e.g., but not limited to the ones from Thermo Scientific or Piercenet, Rockford, Ill.) can be used as a linker molecule herein. 
     In some embodiments, the term “linker” as used herein can be a physical substrate. In some embodiments, the physical substrate is a particle. The particle can be of any shape, e.g., spheres; rods; shells; beads, tubes, wires, and prisms; and these particles can be part of a network. 
     The particles can be made of any materials. In some embodiments, the particle can comprise a material selected from the group consisting of metal (e.g., gold, or iron), metal oxides (e.g., iron oxide), plastic, glass, polymer (e.g., polystyrene), and any combinations thereof. 
     For in vivo purposes, e.g., disease and/or pathogen diagnosis and/or targeted drug delivery, the polymer can be biocompatible and/or biodegradable. The term “biocompatible polymer” refers to polymers which, in the amounts employed, are non-toxic and substantially non-immunogenic when used internally in the patient and which are substantially insoluble in the body fluid of the mammal. Examples of non-biodegradable biocompatible polymers include, by way of example, cellulose acetates (including cellulose diacetate), ethylene vinyl alcohol copolymers, hydrogels (e.g., acrylics), polyacrylonitrile, polyvinylacetate, cellulose acetate butyrate, nitrocellulose, copolymers of urethane/carbonate, copolymers of styrene/maleic acid, and any combinations thereof. Biodegradable polymers are known in the art, e.g., without limitations, linear-chain polymers such as polylactides, polyglycolides, polycaprolactones, polyanhydrides, polyamides, polyurethanes, polyesteramides, polyorthoesters, polydioxanones, polyacetals, polyketals, polycarbonates, polyorthocarbonates, polyphosphazenes, polyhydroxybutyrates, polyhydroxyvalerates, polyalkylene oxalates, polyalkylene succinates, poly(malic acid), poly(amino acids), polyvinylpyrrolidone, polyethylene glycol, polyhydroxycellulose, chitin, chitosa, and copolymers, terpolymers and any combinations thereof. Other biodegradable polymers include, for example, fibrin, gelatin, collagen, and any combinations thereof. 
     The particles can be of any size for the purpose of various aspects described herein, provided that the particle size does not significantly affect the diffusion property of the detection reagent. For example, the particle size can range from 5 nm to 1 mm, from about 10 nm to about 500 μm, or from about 50 nm to about 250 μm. In some embodiments, a particle described herein is a nanoparticle or a microparticle. As used herein, the term “nanoparticle” refers to particles that are on the order of 10 −9  or one billionth of a meter and below 10′ or 1 millionth of a meter in size. The term “microparticle” as used herein refers to particles that are on the order of 10 −6  or one millionth of a meter and below 10 −3  or 1 thousandth of a meter in size. In some embodiments, the particle can be selected from a group consisting of a gold nanoparticle or microparticle, a paramagnetic nanoparticle or microparticle, a magnetic nanoparticle or microparticle, a polystyrene nanoparticle or microparticle, a nanotube or a microtube, a nanowire or a microwire, and any combinations thereof. 
     The particles can be adapted to possess at least one additional property, depending on various applications. In some embodiments, the particles can be adapted to be magnetic responsive or paramagnetic-responsive, e.g., magnetic or paramagnetic particles. In some embodiments, the particles can be adapted to be a delivery vehicle. For example, in some embodiments, the particles can be encapsulated with a therapeutic agent, e.g., for targeted drug delivery to treat a disease or disorder. 
     In some embodiments, the particles can be modified. For example, the particles can be conjugated with proteins, peptides, nucleic acids, or any combinations thereof. In one embodiment, the particles can be surface-conjugated or coated with one member of the binding pair as described above (e.g., for biotin-streptavidin interaction, streptavidin-coated particles can be used for the purpose of various aspects described herein). In some embodiments, the particles can be surface-activated with functional groups (e.g., but not limited to, amine, carboxylic acid, epoxy, tosyl, silane, and any combinations thereof), e.g., to provide binding sites for probe reagents and/or nucleic acid labels. Methods for surface modifications of particles, such as nanoparticles or microparticles, are well known in the art. One of skill in the art can readily modify or activate the surface of particles using any art-recognized reactions, e.g., covalently through crosslinkers, or through protein interaction. 
     The particles described herein can be used in conjunction with the organic linker described above, to form a conjugate linker, or the particles can be used alone as a linker. Both the nucleic acid labels and the probe reagents can be coupled to the particles using a multitude of methods. These include, but are not limited to, direct covalent attachment such as using chemical crosslinkers based on chemistries such as NHS, maleimide, tosyl, isocyanide, etc.; chemical linkage such as using EDC chemistry, thiol adsorption to gold, vinyl/acrylate radical reaction, acrylate-based addition (of e.g., thiols); and protein mediated couplings based on proteins such as streptavidin (and its relatives such as avidin, neutravidin, etc.), protein A, and secondary antibodies, and any combinations thereof. 
     The particles can act as hubs that facilitate a conjugation of multiple nucleic acid labels to single or multiple probes. Depending on applications and/or properties of nucleic acid labels and/or probe reagents, particles can be used as hubs for multi-conjugation. For example, in some embodiments, by acting as a hub, the particles can allow multiple nucleic acid labels to be present at each location (e.g., location of a target molecule or analyte) where the probe binds. Accordingly, the signal generated from the detection reagent can be amplified and thus greater than if only a single label was present. This is especially desirable where antigens/targets or analytes are sparse in a sample. 
     In some embodiments, the particles can allow multiple probes to be arranged in proximity to each other. Thus, the particles can allow several weaker binding events to combine into strong binding. This “avidity action” can transform probe reagents with individually weak affinities into effective sensors. 
     In some embodiments, by acting as a hub, the particles can allow each probe reagent to conjugate to multiple nucleic acid labels. This capability can eliminate the need for other amplification methods (e.g., rolling circle amplification) as multiple nucleic acid labels corresponding to a probe reagent can be used as a form of signal amplification. In some embodiments, this capability can also be used to separate the detection reagents with one nucleic acid label from the ones with different nucleic acid labels, which can, in turn, enable, for example, sequencing by single-base extension. Furthermore, different nucleic acid labels can be conjugated to the particles at controlled ratios, and the ratios can encode additional information. By way of example only, to capture in situ information of one or more enzymes&#39; behavior (e.g., relative enzyme concentration) in the presence of an analyte, two or more different nucleic acid labels can be conjugated to the particles, wherein a subpopulation of the nucleic acid labels corresponding to the probe reagent is not cleavable, while other subpopulations of the nucleic acid labels are each adapted to be cleavable in the presence of their respective enzymes. In such embodiments, the cleavable nucleic acid labels can be conjugated to the particles by cleavable peptide bonds specific for corresponding enzymes. By comparing the ratios of signals generated from the various nucleic acid labels, one would be able to determine the relative enzyme concentrations in the presence of an analyte. 
     The arrangement of the probe reagent(s) and/or nucleic acid label(s) on the particles can vary with a number of factors, e.g., applications, properties of probe reagents and/or nucleic acid labels, sample properties, and/or analytes of interests. In some embodiments, the probe reagents and nucleic acid labels can be conjugated to the particle directly (see, e.g.,  FIG.  4 A ). In some embodiments, one component can be linked to the particle through the other. In such embodiments, the probe reagents can be conjugated or linked to the particle through the nucleic acid labels (see, e.g.,  FIG.  4 B ), e.g., to allow the probe reagents being more accessible by the corresponding analytes in a sample. 
     In some embodiments, the detection reagents can further comprise at least one substrate linker conjugated to the particle. In such embodiment, the substrate linker can allow the detection reagents to be immobilized to a solid support or substrate. 
     Detectable Molecules or Detectable Labels 
     A detectable molecule or detectable label can be covalently attached to a decoder probe or complementary nucleobase before or after the decoder probe or the complementary nucleobase is attached to the pre-determined subsequences or hybridization sites of a nucleic acid label. For example, in attaching a detectable label to a decoder probe, the label can be covalently attached by incorporation of a nucleotide containing a detectable label into the nucleic acid during its synthesis, but before it is hybridized the pre-determined subsequence of the nucleic acid label. Alternatively, during the synthesis of a decoder probe sequence, a nucleotide containing a detectable label acceptor group can be included, and the detectable label can be added to the decoder probe after its synthesis, either before or after it is hybridized to the pre-determined subsequences of the nucleic acid label. Alternatively, the detectable label can be indirectly attached to the decoder probe, for example, by incorporating a nucleotide containing a ligand-binding molecule (e.g., biotin) into the decoder probe during synthesis, and by adding a ligand (e.g., streptavidin) that is covalently attached to the detectable molecule, or vice versa. 
     In some embodiments, the ratios of a detectable label to a decoder probe can range from about 1:1 to about 100:1, from 1:1 to about 50:1, from about 1:1 to about 25:1, from about 1:1 to about 10:1, or from about 1:1 to about 5:1. When a decoder probe comprises more than one detectable label, each detectable label can be attached to a nucleotide of the decoder probe. 
     A detectable label or a detectable molecule can be attached to any nucleotide including both natural and non-natural nucleotides. A nucleotide contains three parts, a phosphate group, a pentose five-carbon sugar molecule, and an organic base. In RNA, the pentose is ribose and in DNA it is deoxyribose and so nucleotides for incorporation into RNA are called ribonucleotides and nucleotides for incorporation into DNA are called deoxyribonucleotides. Three bases adenine, guanine, and cytosine are found in both DNA and RNA while thymine is normally found only in DNA and uracil is normally found only in RNA. Nucleotides can have one, two or three attached phosphate groups and are sometimes referred to as nucleoside phosphates. Nucleotides can contain modified nucleosides having modified bases (e.g., 5-methyl cytosine) and modified sugar groups (e.g., 2′O-methyl ribosyl, 2′O-methoxyethyl ribosyl, 2′fluoro ribosyl, 2′amino ribosyl, and the like). An example of non-natural bases that are used in the art are isocytidine and isoguanine. 
     A detectable label or a detectable molecule as used herein is intended to mean an individual measurable moiety, such as a radioisotope, fluorochrome, dye, enzyme (including its effect on a substrate), nanoparticle, chemiluminescent marker, biotin, or other moiety known in the art that is measurable by analytical methods. A detectable label or a detectable molecule can be attached to a nucleotide using methods well known in the art and exemplified herein. 
     Without limitations, examples of a detectable label or a detectable molecule that can be utilized by some aspects described herein can include optical reporters or optical labels. Suitable optical reporters or optical labels include, but are not limited to, fluorescent reporters and chemiluminescent groups. A wide variety of fluorescent reporter dyes are known in the art. Typically, the fluorophore is an aromatic or heteroaromatic compound and can be a pyrene, anthracene, naphthalene, acridine, stilbene, indole, benzindole, oxazole, thiazole, benzothiazole, cyanine, carbocyanine, salicylate, anthranilate, coumarin, fluorescein, rhodamine or other like compound. Suitable fluorescent reporters include xanthene dyes, such as fluorescein or rhodamine dyes, including, but not limited to, Alexa Fluor® dyes (InvitrogenCorp.; Carlsbad, Calif.), fluorescein, fluorescein isothiocyanate (FITC), Oregon Green™, rhodamine, Texas red, tetrarhodamine isothiocynate (TRITC), 5-carboxyfluorescein (FAM), 2′7′-dimethoxy-4′5′-dichloro-6-carboxyfluorescein (JOE), tetrachlorofluorescein (TET), 6-carboxyrhodamine (R6G), N,N,N,N′-tetramefhyl-6-carboxyrhodamine (TAMRA), 6-carboxy-X-rhodamine (ROX). Suitable fluorescent reporters also include the naphthylamine dyes that have an amino group in the alpha or beta position. For example, naphthylamino compounds include 1-dimethylamino-naphthyl-5-sulfonate, 1-anilino-8-naphthalene sulfonate, 2-p-toluidinyl-6-naphthalene sulfonate, and 5-(2′-aminoethyl)aminonaphthalene-1-sulfonic acid (EDANS). Other fluorescent reporter dyes include coumarins, such as 3-phenyl-7-isocyanatocoumarin; acridines, such as 9-isothiocyanatoacridine and acridine orange; N-(p(2-benzoxazolyl)phenyl)maleimide; cyanines, such as Cy2, indodicarbocyanine 3 (Cy3), indodicarbocyanine 5 (Cy5), indodicarbocyanine 5.5 (Cy5.5), 3-(-carboxy-pentyl)-3′ethyl-5,5′-dimethyloxacarbocyanine (CyA); 1H,5H,11H, 15H-Xantheno [2,3,4-ij:5,6,7-i′j′]diquinolizin-18-ium, 9-[2(or 4)-[[[6-[2,5-dioxo-1-pyrrolidinyl)oxy]-6-oxohexyl] amino] sulfonyl]-4(or 2)-sulfophenyl]-2,3,6,7,12,13,16,17octahydro-inner salt (TR or Texas Red); BODIPY™ dyes; benzoxadiazoles; stilbenes; pyrenes; and the like. Many suitable forms of these fluorescent compounds are available and can be used. 
     Examples of fluorescent proteins suitable for use as imaging agents include, but are not limited to, green fluorescent protein, red fluorescent protein (e.g., DsRed), yellow fluorescent protein, cyan fluorescent protein, blue fluorescent protein, and variants thereof (see, e.g., U.S. Pat. Nos. 6,403,374, 6,800,733, and 7,157,566). Specific examples of GFP variants include, but are not limited to, enhanced GFP (EGFP), destabilized EGFP, the GFP variants described in Doan et al,  Mol. Microbiol,  55:1767-1781 (2005), the GFP variant described in Crameri et al,  Nat. Biotechnol.,  14:315319 (1996), the cerulean fluorescent proteins described in Rizzo et al,  Nat. Biotechnol,  22:445 (2004) and Tsien,  Annu. Rev. Biochem.,  67:509 (1998), and the yellow fluorescent protein described in Nagal et al,  Nat. Biotechnol.,  20:87-90 (2002). DsRed variants are described in, e.g., Shaner et al,  Nat. Biotechnol.,  22:1567-1572 (2004), and include mStrawberry, mCherry, morange, mBanana, mHoneydew, and mTangerine. Additional DsRed variants are described in, e.g., Wang et al,  Proc. Natl. Acad. Sci. U.S.A.,  101:16745-16749 (2004) and include mRaspberry and mPlum. Further examples of DsRed variants include mRFPmars described in Fischer et al,  FEBS Lett.,  577:227-232 (2004) and mRFPruby described in Fischer et al,  FEBS Lett,  580:2495-2502 (2006). 
     Amine-reactive and thiol-reactive fluorophores are available and generally used for labeling nucleotides and biomolecules. In some embodiments, nucleotides are fluorescently labeled during chemical synthesis, for example, incorporation of amines or thiols during nucleotide synthesis permit addition of fluorophores. Fluorescently labeled nucleotides are commercially available. For example, uridine and deoxyuridine triphosphates are available that are conjugated to ten different fluorophores that cover the spectrum. 
     In some embodiments, radioisotopes can be utilized as detectable molecules or detectable molecules for labeling nucleotides including, for example,  32 P,  33 P,  35 S,  3 H, and  125 I. These radioisotopes have different half-lives, types of decay, and levels of energy which can be tailored to match the needs of a particular experiment. For example,  3 H is a low energy emitter which results in low background levels, however this low energy also results in long time periods for autoradiography. Radioactively labeled ribonucleotides and deoxyribonucleotides are commercially available. Nucleotides are available that are radioactively labeled at the first, or α, phosphate group, or the third, or γ, phosphate group. For example, both [α- 32 P]dATP and [γ- 32 P]dATP are commercially available. In addition, different specific activities for radioactively labeled nucleotides are also available commercially and can be tailored for different experiments. 
     Suitable non-metallic isotopes include, but are not limited to,  11 C,  14 C,  13 N,  18 F,  123 I,  124 I, and  125 I. Suitable radioisotopes include, but are not limited to,  99 mTc,  95 Tc,  111 In,  62 Cu,  64 Cu, Ga,  68 Ga, and  153 Gd. Suitable paramagnetic metal ions include, but are not limited to, Gd(III), Dy(III), Fe(III), and Mn(II). Suitable X-ray absorbers include, but are not limited to, Re, Sm, Ho, Lu, Pm, Y, Bi, Pd, Gd, La, Au, Au, Yb, Dy, Cu, Rh, Ag, and Ir. In some embodiments, the radionuclide is bound to a chelating agent or chelating agent-linker attached to the aggregate. Suitable radionuclides for direct conjugation include, without limitation,  18 F,  124 I,  125 I,  131 I, and mixtures thereof. Suitable radionuclides for use with a chelating agent include, without limitation,  47 Sc,  64 Cu,  67 Cu,  89 Sr,  86 Y,  87 Y,  90 Y,  105 Rh,  111 Ag,  111 In,  117 mSn,  149 Pm,  153 Sm,  166 Ho,  177 Lu,  186 Re,  188 Re,  211 At,  212 Bi, and mixtures thereof. Suitable chelating agents include, but are not limited to, DOTA, BAD, TETA, DTPA, EDTA, NTA, HDTA, their phosphonate analogs, and mixtures thereof. One of skill in the art will be familiar with methods for attaching radionuclides, chelating agents, and chelating agent-linkers to the particles. 
     Non-radioactive and non-fluorescent label monomers are also available. For example, biotin can be attached directly to nucleotides and detected by specific and high affinity binding to avidin or streptavidin which has been chemically coupled to an enzyme catalyzing a colorimetric reaction (such as phosphatase, luciferase, or peroxidase). Digoxigenin labeled nucleotides can also similarly be used for non-isotopic detection of nucleic acids. Biotinylated and digoxigenin-labeled nucleotides are commercially available. 
     In some embodiments, enzymatic reaction on a substrate can be utilized a detection method. In such embodiments, enzymes (e.g., horseradish peroxidase or alkaline phosphatase) can be linked to a nucleotide of a nucleic acid label and/or decoder probe. During detection, a substrate on which the particular enzyme reacts can be added to induce a colorimetric reaction. Any enzyme-substrate reactions known in the art can be used herein. 
     Very small particles, termed nanoparticles, also can be used as detectable labels or detectable molecules to label decoder probes or any nucleic acids. These particles range from 1-1000 nm in size and include diverse chemical structures such as gold and silver particles and quantum dots. 
     When irradiated with angled incident white light, silver or gold nanoparticles ranging from 40-120 nm will scatter monochromatic light with high intensity. The wavelength of the scattered light is dependent on the size of the particle. Four to five different particles in close proximity will each scatter monochromatic light which when superimposed will give a specific, unique color. Alternatively, the gold nanoparticles can be detected or “developed” using a silver-based developer such that the tiny nanoparticle can be detected easily, even with naked eyes. The particles are being manufactured by companies such as Genicon Sciences. Derivatized silver or gold particles can be generally attached to a broad array of molecular molecules including, proteins, antibodies, small molecules, receptor ligands, and nucleic acids. For example, the surface of the particle can be chemically derivatized to allow attachment to a nucleotide, which can then be incorporated into a decoder probe. 
     Another type of nanoparticle that can be used as a detectable molecule or detectable label are quantum dots. Quantum dots are fluorescing crystals 1-5 nm in diameter that are excitable by a large range of wavelengths of light. These crystals emit light, such as monochromatic light, with a wavelength dependent on their chemical composition and size. Quantum dots such as CdSe, ZnSe, InP, or InAs possess unique optical properties. 
     Due to their very small size the quantum dots can be generally coupled into oligonucleotides directly without affecting the solubility or use of the oligonucleotide. Thus, quantum dots can be coupled to decoder probes as described herein. To synthesize a decoder probe-quantum dot complex by conventional batch chemistry, both the decoder probe and the quantum dot require at least a reactive group of different kinds that can be reacted with each other. For example, if a decoder probe has an amino group and a quantum dot has an aldehyde group, these groups can react to form a Schiff base. A decoder probe can be derivatized to attach a single amino or other functional group using chemistry well known in the art. When a quantum dot is derivatized, the quantum dot can be covered with a chemical reagent which results in coating the entire surface of the nanoparticle with several functional groups. 
     A detectable molecule or detectable label can be attached to a nucleotide of a decoder probe or nucleic acid using a variety of methods well known in the art and described herein. For example, the detectable molecule or detectable label can be directly attached to the nucleotide in a 1:1 correspondence by incorporation of a radioactive phosphate into the phosphate backbone of the nucleotide. Also, for example, a general method for labeling phosphates with a fluorescent label that employs an imidazole derivative prepared from a BODIPY FL hydrazide has been reported (Wang and Giese, Anal. Chem. 65: 3518 (1993). 
     Depending on the labeling moiety used, it can be desirable to derivatize or chemically modify a nucleotide in order to bind the label monomer. These methods and chemistries are known in the art. In addition, a linker can be used to attach a detectable molecule or detectable label to a nucleotide in a 1:1 correspondence. For example, a fluorescently labeled nucleotide such as fluorescein-12-dUTP can have a fluorophore monomer attached via a four-atom aminoalkynyl group to the dUTP molecule. 
     These nucleotides attached to detectable molecules or detectable labels can be incorporated into a decoder probe or nucleic acid using several methods for labeling nucleic acids well known in the art. For example, enzymes such as DNA or RNA polymerases, Taq polymerases, terminal deoxynucleotidyl transferases, or reverse transcriptases can be used to incorporate labeled nucleotides into decoder probes or nucleic acids. 
     Labeled nucleotides can be incorporated into decoder probe sequences or nucleic acids, for example, by nick translation. In this procedure DNAse I is used to create single-strand nicks in double stranded DNA and then the 5′ to 3′ exonuclease and 5′ to 3′ polymerase actions of  E. coli  DNA polymerase I are used to remove stretches of single stranded DNA starting at the nicks and replace them with new strands made by incorporation of labeled nucleotides. Nick translation can utilize any labeled nucleotide including radioactively labeled nucleotides and biotinylated or digoxigenin labeled nucleotides. In a similar way T4 DNA polymerase can be used to incorporate labeled nucleotides. In addition, labeled nucleotides can be incorporated into nucleic acids using the polymerase chain reaction (PCR) and Taq polymerases. The degree of labeling can be controlled by including one, or up to all four labeled nucleotides. In addition, the degree of labeling can be controlled by increasing or decreasing the concentration of the labeled nucleotide(s). 
     Other methods for labeling decoder probes or nucleic acids include generating single-stranded cDNA from RNA by using a reverse transcriptase in the presence of labeled nucleotides. In addition, DNA can be cloned into a vector with SP6 or T7 polymerase sites. Transcription in the presence of SP6 or T7 RNA polymerase and labeled nucleotides results in a labeled RNA transcript. The transcript can be labeled to different degrees by including one or more labeled nucleotides. In addition, several nucleotides within a nucleic acid can be labeled, for example, by cloning DNA into a bacteriophage M13 based vector. Then the Klenow fragment of DNA polymerase I and the M13 universal probe primer can be used to synthesize the complementary stand with incorporation of labeled nucleotides. 
     Several methods are described above for incorporation of labeled nucleotides into newly synthesized decoder probes or nucleic acids. Existing nucleic acids can also be labeled using several methods known in the art. For example, RNA or DNA can be end-labeled with [γ-32P]ATP and T4 polynucleotide kinase. This kinase can be used to transfer the radioactive phosphate of ATP to a free 5′ OH group in either DNA or RNA. The enzyme also has a phosphatase activity and so two reactions are possible. In the forward reaction, the enzyme catalyzes phosphorylation following removal of 5′ terminal phosphates with alkaline phosphatase (or other phosphatase). In the exchange reaction, the kinase catalyzes the exchange of an existing 5′ phosphate with the third or γ phosphate of ATP. The latter reaction is carried out in the presence of excess ATP and ADP for efficient phosphorylation. Using this method the radioactive phosphate of ATP is transferred to the end of the nucleic acid molecule. Decoder probes or nucleic acids can also be labeled with terminal deoxynucleotidyl transferase which adds labeled nucleotides onto the 3′ end of DNA fragments. Both single and double-stranded DNAs are substrates for this enzyme. The large (Klenow) fragment of  E. coli  DNA polymerase I can also be used to label the ends of decoder probes or nucleic acids. Since this enzyme has a 5′ to 3′ polymerase activity it can be used to “fill in” the 3′ ends of nucleic acid (e.g., DNA) fragments opposite of 5′ extensions or overhangs with labeled nucleotides. End-labeling of decoder probes or nucleic acids using polynucleotide kinase or terminal deoxynucleotidyl transferase results in the incorporation of one detectable label or detectable molecule per nucleic acid. The “fill in” reaction can be used to label the decoder probe or nucleic acid at one nucleotide per nucleic acid or at more than one nucleotide per nucleic acid. 
     In addition, decoder probes or nucleic acids can be labeled by modification of nucleotides within the nucleic acid sequences. For example, cytidine residues in DNA and RNA can be modified by reaction with sodium bisulfite to form sulfonate intermediates that can then be directly coupled to hydrazides or aliphatic amines. Virtually any of the fluorescent, biotin or other hydrazides or aliphatic amines can be used in this reaction. The bisulfite-activated cytidylic acid can also be coupled to aliphatic diamines such as ethylenediamine. The amine-modified nucleic acids (e.g., DNA or RNA) can then be modified with any of the amine-reactive dyes. In addition, phosphate groups can be targeted in nucleic acids for labeling. Although phosphate groups of nucleotides are not very reactive in aqueous solution, their terminal phosphate groups can react with carbodiimides and similar reagents in combination with nucleophiles to yield labeled phsophodiesters, phosphoramidates and phosphorothioates. For example, nucleic acids (e.g., DNA) can be reacted quantitatively with carbonyl diimidazole and a diamine such as ethylenediamine to yield a phosphoramidate that has a free primary amine and that this amine can then be modified with amino-reactive reagents. Fluorescent or biotinylated amines have been coupled to the 5′ phosphate of tRNA using dithiodipyridine and triphenylphosphine. 
     The bond between detectable molecules or detectable labels and decoder probes or nucleic acids can be covalent bonds or non-covalent bonds that are stable to hybridization. The detectable molecules or detectable labels can be bound to a decoder probe or a nucleic acid in a sequence specific manner, for example by the incorporation of a labeled nucleotide into a sequence that has been digested by a restriction enzyme. Alternatively the detectable molecules or detectable labels can be bound to a decoder probe or a nucleic acid in a non-sequence specific manner, for example by the incorporation of a label onto the terminal phosphate of a nucleic acid using [γ- 32 P]ATP and T4 polynucleotide kinase. 
     Synthesis of Nucleic Acids (e.g., for at Least Part of the Nucleic Acid Label Such as Pre-Determined Subsequences and/or Decoder Probe Sequences 
     The nucleic acids described herein can be chemically synthesized using naturally occurring nucleotides or variously modified nucleotides designed to increase the biological stability of the molecules or to increase the physical stability of the duplex formed between the label attachment region and the annealed complementary polynucleotide sequences or segments, e.g., phosphorothioate derivatives and acridine substituted nucleotides can be used. Examples of modified nucleotides which can be used to generate the synthetic nucleic acid include 5-fluorouracil, 5-bromouracil, 5-chlorouracil, 5-iodouracil, hypoxanthine, xanthine, 4-acetylcytosine, 5-(carboxyhydroxylmethyl)uracil, 5-carboxymethylaminomethyl-2-thiouridine, 5-carboxymethylaminomethyluracil, dihydrouracil, beta-D-galactosylqueosine, inosine, N6-isopentenyladenine, 1-methylguanine, 1-methylinosine, 2,2-dimethylguanine, 2-methyladenine, 2-methylguanine, 3-methylcytosine, 5-methylcytosine, N6-adenine, 7-methylguanine, 5-methylaminomethyluracil, 5-methoxyaminomethyl-2-thiouracil, beta-D-mannosylqueosine, 5′-methoxycarboxymethyluracil, 5-methoxyuracil, 2-methylthio-N-6-isopentenyladenine, uracil oxyacetic acid (v), wybutoxosine, pseudouracil, queosine, 2-thiocytosine, 5-methyl-2-thiouracil, 2-thiouracil, 4-thiouracil, 5-methyluracil, uracil-5-oxyacetic acid methylester, uracil-5-oxyacetic acid (v), 5-methyl-2-thiouracil, 3-(3-amino-3-N2-carboxypropyl)uracil, (acp3)w, and 2,6-diaminopurine. 
     Alternatively, the synthetic nucleic acid can be produced biologically using a vector into which a nucleic acid has been subcloned. As one example, a linear single-stranded DNA backbone can be made from a double stranded plasmid DNA using a four step protocol that includes (i) linearization of the dsDNA with a restriction enzyme, (ii) dephosphorylation with a thermolabile phosphatase, (iii) digestion with a second restriction enzyme to separate the cloning vector from the backbone sequence, and (iv) digestion with a strand-specific lambda exonuclease digestion, leaving only one strand of the backbone fragment intact. 
     In various embodiments, the nucleic acids can be modified at the base moiety, sugar moiety or phosphate backbone to improve, e.g., the stability, hybridization, or solubility of the molecule. For example, the deoxyribose phosphate backbone of the nucleic acids can be modified to generate peptide nucleic acids (see Hyrup et al, 1996, Bioorganic &amp; Medicinal Chemistry 40:5-23). As used herein, the terms “peptide nucleic acids” or “PNAs” refer to nucleic acid mimics, e.g., DNA mimics, in which the deoxyribose phosphate backbone is replaced by a pseudopeptide backbone and only the four natural nucleobases are retained. The neutral backbone of PNAs has been shown to allow for specific hybridization to DNA and RNA under conditions of low ionic strength. The synthesis of PNA oligomers can be performed using standard solid phase peptide synthesis protocols as described in Hyrup et al, 1996, Bioorganic &amp; Medicinal Chemistry 4(1): 5-23; Perry-O&#39;Keefe et al., 1996, Proc. Natl. Acad. Sci. USA 93: 14670-675. 
     In an exemplary embodiment, the selected novel nucleic acid sequence (e.g., DNA sequence) can be constructed synthetically as double-stranded nucleic acid by a commercial gene synthesis company and cloned in an oriented fashion into a “phagemid”, a plasmid vector containing an M13 or f1 phage intergenic (IG) region which contains the cis-acting sequences necessary for nucleic acid (e.g., DNA) replication and phage encapsidation, such as pUC119. The appropriate orientation of the cloned insert relative to the phage origin of replication allows for the generation of a single-stranded DNA backbone which is the reverse complement of the RNA molecules generated by in vitro transcription for each label attachment region. 
     In order to generate the single-stranded nucleic acid (e.g., DNA) backbone (e.g., of at least part of the nucleic acid label and/or decoder probes), the phagemid is transformed into an  E. coli  strain containing an F′ episome. Subsequent infection of the transformed bacteria with a helper phage such as the M113 mutant K07 results in the secretion of the phagemid carrying the single-stranded nucleic acid sequence, packaged phage from which the circular, single-stranded nucleic acid is prepared using a standard protocol. This nucleic acid is linearized and the vector portion is excised by annealing short, complementary oligonucleotides to either end of the single-strander nucleic acid sequence to generate double-stranded restriction sites, followed by treatment with the appropriate restriction enzymes. 
     Analytes or Target Molecules 
     The terms “analyte,” “target analyte,” and “target molecule”, as used interchangeably herein, refer to the molecule detected, identified or measured by binding of a detection reagent described herein whose probe reagent(s) recognize (i.e., are specific binding partners) thereto. In some embodiments, a target molecule or an analyte can be, but is not limited to, any of the following or any combinations of the following: nucleic acid, peptide, a polypeptide/protein (e.g., a bacterial or viral protein or an antibody), a lipid, a carbohydrate, a glycoprotein, a glycolipid, a small molecule, an organic monomer, sugar, peptidoglycan, a cell, a virus or a drug. Nucleic acids that can be analyzed by the methods herein include: double-stranded DNA, single-stranded DNA, single-stranded DNA hairpins, DNA/RNA hybrids, RNA (e.g. mRNA or miRNA) and RNA hairpins. Generally, a target molecule can be a naturally occurring molecule or a cDNA of a naturally occurring molecule or the complement of said cDNA. In other embodiments, a target molecule can be modified, e.g., by mutation or chemical reaction. In some embodiments, a target molecule can be synthetic or recombinant. 
     In some embodiments, an analyte can be an analyte comprising at least one post-translational modification, e.g., phosphorylations and/or glycosylations. 
     A target molecule or an analyte can be part of a sample that contains other components or can be the sole or major component of the sample. A target molecule or an analyte can be a component of a whole cell, tissue or body fluid, a cell or tissue extract, a fractionated lysate thereof or a substantially purified molecule. The target molecule can be present in solution or attached to a solid substrate, including, for example, to a solid surface such as a chip, microarray, bead or a blotting membrane. Also the target molecule or analyte can have either a known or unknown structure or sequence. 
     Sample 
     The methods, detection reagents and kits described herein can be used to analyze a sample from any sources, e.g., but not limited to biological samples (e.g., collected from organisms, animals or subjects), environmental samples, food, food byproduct, soil, archaeological samples, extraterrestrial samples, or any combinations thereof. 
     In some embodiments, the term “sample” refers to a biological sample. The term “biological sample” as used herein denotes a sample taken or isolated from a biological organism, e.g., tissue cell culture supernatant, cell lysate, a tissue sample (e.g., biopsy), a homogenate of a tissue sample from a subject or a fluid sample from a subject. Exemplary biological samples include, but are not limited to, blood, sputum, urine, cerebrospinal fluid, urine, sweat, mucus, nasal discharge, vaginal fluids, spinal fluid, pleural fluid, nipple aspirates, lymph fluid, the external sections of the skin, respiratory, intestinal, and genitourinary tracts, tears, saliva, milk, feces, sperm, cells or cell cultures, serum, leukocyte fractions, smears, tissue samples of all kinds, plants and parts of plants, microorganisms (such as bacteria), viruses (such as cytomegalo virus, HIV, hepatitis B, hepatitis C, hepatitis 6 virus), yeasts, embryos, fungi, cell-free sample material, etc. The term also includes both a mixture of the above-mentioned samples such as fungus-infected plants or whole human blood containing mycobacteria as well as food samples that contain free or bound nucleic acids, or proteins, or cells containing nucleic acids or proteins, environmental samples which contain free or bound nucleic acids, or proteins, or cells containing nucleic acids or proteins. The term “biological sample” also includes untreated or pretreated (or pre-processed) biological samples. 
     A “biological sample” can contain cells from subject, but the term can also refer to non-cellular biological material, such as non-cellular fractions of blood, saliva, or urine, that can be used to measure gene expression levels. In some embodiments, the sample is from a resection, bronchoscopic biopsy, or core needle biopsy of a primary or metastatic tumor, or a cell block from pleural fluid. In addition, fine needle aspirate samples can be used. Samples can be either paraffin-embedded or frozen tissue. In some embodiments, a biological sample can comprise a biopsy, a surgically removed tissue, a swap, or any combinations thereof. 
     The sample can be obtained by removing a sample of cells from a subject, but can also be accomplished by using previously isolated cells (e.g. isolated by another person). In addition, the biological sample can be freshly collected or a previously collected sample. Furthermore, the biological sample can be utilized for the detection of the presence and/or quantitative level of a biomolecule of interest. Representative target analytes include, but are not limited to nucleic acids, proteins, and derivatives and fragments thereof. 
     In some embodiments, the biological sample is an untreated biological sample. As used herein, the phrase “untreated biological sample” refers to a biological sample that has not had any prior sample pre-treatment except for dilution and/or suspension in a solution. Exemplary methods for treating a biological sample include, but are not limited to, centrifugation, filtration, sonication, homogenization, heating, freezing and thawing, and any combinations thereof. 
     In accordance with some embodiments of various aspects described herein, a biological sample can be pre-processed, as described earlier, before employing the detection reagents and the methods described herein. In some embodiments, the biological sample can be filtered before isolating a cellular material according to the methods, apparatus and kits described herein. 
     In some embodiments, the biological sample can be treated with a chemical and/or biological reagent. Chemical and/or biological reagents can be employed to protect and/or maintain the stability of the sample or target analytes during processing. In addition, or alternatively, chemical and/or biological reagents can be employed to release or expose target analytes from other components of the sample. One exemplary reagent is a protease inhibitor, which is generally used to protect or maintain the stability of the target analytes during processing. 
     In some embodiments, the term “sample” as used herein can refer to an environmental sample (including, but not limited to, air, agricultural (e.g., but not limited to hydrofarms or hydroponic samples), pond, water, wastewater, and soil samples); biological warfare agent samples; research samples including extracellular fluids. In some embodiments, an environmental sample can comprise a sample collected from a working surface of an equipment or machine (e.g., but not limited to, food or pharmaceutical product processing equipment or machine), a device (e.g., but not limited to, biomedical devices, implantation devices, fluid delivery devices such as a tubing, and/or a catheter), and/or a building or dwellings (e.g., but not limited to, food processing plants, pharmaceutical manufacturing plants, hospitals, and/or clinics). 
     In some embodiments, a sample can comprise food (e.g., solid and/or fluid food as well as processed food) and/or food byproduct. For example, the methods, detection reagents and kits described herein can be used to detect an analyte, e.g., a particular nutrient, in food and/or food byproduct, e.g., but not limited to, meat, milk, yoghurt, bread, starch-based products, vegetables, and any combinations thereof. In some embodiments, the methods, detection reagents and kits described herein can be used to detect a contaminant, e.g., bacteria, fungus, spores, molds, and/or viruses, in food and/or food byproduct. 
     In some embodiments, a sample can comprise a pharmaceutical product (e.g., but not limited to pills, tablets, gel capsules, syrups, vaccines, liquids, sprays, and any combinations thereof). For example, the methods, detection reagents and kits described herein can be used to detect the presence and/or measure the level of a particular active agent present in a pharmaceutical product. In some embodiments, the methods, detection reagents and kits described herein can be used to detect a contaminant, e.g., bacteria, fungus, spores, molds, and/or viruses, in a pharmaceutical product. 
     In some embodiments, a sample can comprise an archaeological sample. In some embodiments, an archaeological sample can be obtained or collected from artifacts, architecture, biofacts (or ecofact, e.g., an object found at an archaeological site), cultural landscapes, and any combinations thereof. 
     In some embodiments, a sample can comprise an extraterrestrial sample. For example, an extraterrestrial sample can be any object or specimen (e.g., rock, meteorite, and/or environmental samples) obtained or collected from outer space or universe, and/or planets beyond the planet Earth, e.g., the moon, other planets (e.g., but not limited to, Mars, and/or Jupiter) and/or non-stellar objects. 
     Applications of the Detection Reagents 
     The detection reagents, compositions, methods and kits described herein can be used for diagnostic, prognostic therapeutic and screening purposes. The inventions described herein provide the advantage that many different target analytes can be analyzed at one time from a single sample using the methods described herein. This allows, for example, for several diagnostic tests to be performed on one sample. 
     When the probe reagent is a nucleic acid, the methods described herein can discriminate between nucleotide sequences. The difference between the target nucleotide sequences can be, for example, a single nucleic acid base difference, a nucleic acid deletion, a nucleic acid insertion, or rearrangement. Such sequence differences involving more than one base can also be detected. In some embodiments, the oligonucleotide probe sets have substantially the same length so that they hybridize to target nucleotide sequences at substantially similar hybridization conditions. As a result, the process described herein is able to detect various kinds of diseases or disorders, e.g., but not limited to, infectious diseases, genetic diseases, and cancer. 
     Without wishing to be bound, the detection reagents, compositions, methods and kits described herein can also be used for environmental monitoring, forensics, and food science. Examples of genetic analyses that can be performed on nucleic acids include e.g., SNP detection, STR detection, RNA expression analysis, promoter methylation, gene expression, virus detection, viral subtyping and drug resistance. 
     In the area of environmental monitoring, some embodiments of various aspects described herein can be used for detection, identification, and monitoring of pathogenic and indigenous microorganisms in natural and engineered ecosystems and microcosms such as in municipal waste water purification systems and water reservoirs or in polluted areas undergoing bioremediation. It can also be used to detect plasmids containing genes that can metabolize xenobiotics, to monitor specific target microorganisms in population dynamic studies, or either to detect, identify, or monitor genetically modified microorganisms in the environment and in industrial plants. 
     Some embodiments of various aspects described herein can also be used in a variety of forensic areas, including for human identification for military personnel and criminal investigation, paternity testing and family relation analysis, HLA compatibility typing, and screening blood, sperm, or transplantation organs for contamination. 
     In the food and feed industry, some embodiments of various aspects described herein have a wide variety of applications. For example, it can be used for identification and characterization of production organisms such as yeast for production of beer, wine, cheese, yogurt, bread, etc. Another area of use is related to the quality control and certification of products and processes (e.g., livestock, pasteurization, and meat processing) for contaminants. Other uses include the characterization of plants, bulbs, and seeds for breeding purposes, identification of the presence of plant-specific pathogens, and detection and identification of veterinary infections. 
     In some embodiments, the methods, detection reagents and kits described herein can be used to detect the presence and/or measure the level of a particular active agent present in a pharmaceutical product. In some embodiments, the methods, detection reagents and kits described herein can be used to detect a contaminant, e.g., bacteria, fungus, spores, molds, and/or viruses, in a pharmaceutical product. 
     In some embodiments, the methods, detection reagents and kits described herein can be used to detect the presence and/or measure the level of an analyte of interest present in an archaeological sample, e.g., obtained or collected from artifacts, architecture, biofacts (or ecofact, e.g., an object found at an archaeological site), cultural landscapes, and any combinations thereof. 
     In some embodiments, the methods, detection reagents and kits described herein can be used to detect the presence and/or measure the level of an analyte of interest present in an extraterrestrial sample, e.g., any object or specimen (e.g., rock, meteorite, and/or environmental samples) obtained or collected from outer space or universe, and/or planets beyond the planet Earth, e.g., the moon, other planets (e.g., but not limited to, Mars, and/or Jupiter) and/or non-stellar objects. For example, the methods, detection reagents, and kits described herein can be used to analyze the composition of an extratrerresterial sample or specimen, e.g., a rock specimen, a water sample, and/or an air sample. 
     In some embodiments, the detection reagents and methods described herein can be used to detect and/or identify analytes comprising a post-translation modification, e.g., phosphorylation or glycosylation. As such, in some embodiments, the detection reagents and methods described herein can differentiate between multiple different glycosylation forms of recombinant therapeutic proteins 
     Immunohistochemistry: Some embodiments of various aspects described herein can be used to perform antibody-based staining of cell or tissues for microscopic evaluation. This can involve either unfixed or unpermeabilized samples examined for surface or extracellular antigens, or permeabilized samples wherein intracellular antigens are also probed. While very common, immunohistochemistry is typically limited to probing with a small set of antibodies at a time (due to the limitation of available optical colors), and multiple staining cycles are generally avoided, since the stripping of the preceding cycle&#39;s antibodies can damage the sample. Some embodiments of the detection reagents comprising antibodies as probe reagents and nucleic acid labels can allow for many antibodies to be used concurrently, which saves time and sample material, extract more data, and demand less prior knowledge of the sample. In some embodiments, without wishing to be bound by theory, when a subset of the probed antigens can overlap spatially, the detection reagents with a plurality of contiguous pre-determined subsequences (e.g., each pre-determined subsequences contain one nucleotide, as shown in  FIG.  1   ) can be used. 
     In-situ hybridization: Fluorescence in-situ hybridization (FISH) is a technique for detecting (and/or quantifying) the presence of certain cellular DNA or RNA (often ribosomal RNA). As with other fluorescence-based techniques, FISH is limited to the number of colors available to the microscopy. Using some embodiments of the detection reagents and/or methods described herein, the cells can be probed for many sequences simultaneously, thus allowing the user to save time and sample material, extract more data, and demand less prior knowledge of the sample. 
     Expression profiling: Nucleic-acid probe reagents of the detection reagents can target messenger RNA or micro RNA and provide information on the RNA-level expression state of the cell. Using some embodiments of the detection reagents and/or methods described herein, the assay can capture and probe numerous mRNA and/or miRNA at once, reducing and/or eliminating potentially harmful stripping steps. 
     Western blots: Western blots are protein assays wherein proteins are separated electrophoretically, transferred to a membrane and stained. In many cases, the staining is done using one or a few antibodies in order to detect the corresponding antigens in the blot. By using some embodiments of the detection reagents and/or methods described herein, the blot can be simultaneously probed using a large number of antibodies without antibody-stripping steps. This can allow one blot to provide significantly more information than the conventional Western blots where one antibody is usually probed at a time and can require antibody stripping for the next antibody probing, thereby saving sample material and time. 
     Diagnostic/Prognostic Methods: The present methods can be applied to the analysis of biological samples obtained or derived from a patient so as to determine whether a diseased cell type is present in the sample and/or to stage the disease. 
     In some embodiments, the methods described herein are used in the diagnosis of a condition. As used herein the term “diagnose” or “diagnosis” of a condition includes predicting or diagnosing the condition, determining predisposition to the condition, monitoring treatment of the condition, diagnosing a therapeutic response of the disease, and prognosis of the condition, condition progression, and response to particular treatment of the condition. For example, a blood sample can be assayed according to any of the methods described herein to determine the presence and/or quantity of markers of a cancerous cell type in the sample, thereby diagnosing or staging the cancer. 
     In some embodiments, the detection reagents and methods described herein can be directly used as contrast agents for in vivo or in situ diagnosis, in which detection reagents are administered to a subject, either by oral administration or local injection. The probe reagents of the detection reagents can bind to the target analytes, e.g., biomarkers for specific diseases or disorders, and detection of the nucleic acid labels using the methods described herein can then locate the target analytes. In some embodiments, the detection reagents and methods described herein can be used to locate microscopic tumors in a subject, where other conventional methods are not sensitive enough to detect such microscopic tumors. 
     Cancers which can be detected by some embodiments of the process described herein generally involve oncogenes, tumor suppressor genes, or genes involved in DNA amplification, replication, recombination, or repair. Examples of these include: BRCA1 gene, p53 gene, APC gene, Her2/Neu amplification, Bcr/Ab1, K-ras gene, and human papillomavirus Types 16 and 18. Some embodiments of various aspects can be used to identify amplifications, large deletions as well as point mutations and small deletions/insertions of the above genes in the following common human cancers: leukemia, colon cancer, breast cancer, lung cancer, prostate cancer, brain tumors, central nervous system tumors, bladder tumors, melanomas, liver cancer, osteosarcoma and other bone cancers, testicular and ovarian carcinomas, head and neck tumors, and cervical neoplasms. 
     Genetic diseases can also be detected by some embodiments of the process described herein. This can be carried out by prenatal or post-natal screening for chromosomal and genetic aberrations or for genetic diseases. Examples of detectable genetic diseases include: 21 hydroxylase deficiency, cystic fibrosis, Fragile X Syndrome, Turner Syndrome, Duchenne Muscular Dystrophy, Down Syndrome or other trisomies, heart disease, single gene diseases, HLA typing, phenylketonuria, sickle cell anemia, Tay-Sachs Disease, thalassemia, Klinefelter Syndrome, Huntington Disease, autoimmune diseases, lipidosis, obesity defects, hemophilia, inborn errors of metabolism, and diabetes. 
     Alternatively, the methods described herein can be used to diagnose pathogen infections, for example infections by intracellular bacteria and viruses, by determining the presence and/or quantity of markers of bacterium or virus, respectively, in the sample. 
     A wide variety of infectious diseases can be detected by some embodiments of the process described herein. Typically, these are caused by bacterial, viral, parasite, and fungal infectious agents. The resistance of various infectious agents to drugs can also be determined using some embodiments of various aspects described herein. 
     Bacterial infectious agents which can be detected by some embodiments of various aspects described herein can include  Escherichia coli, Salmonella, Shigella, Klebsiella, Pseudomonas, Listeria monocytogenes, Mycobacterium tuberculosis, Mycobacterium aviumintracellulare, Yersinia, Francisella, Pasteurella, Brucella , Clostridia,  Bordetella pertussis, Bacteroides, Staphylococcus aureus, Streptococcus pneumonia , B-Hemolytic strep.,  Corynebacteria, Legionella, Mycoplasma, Ureaplasma, Chlamydia, Neisseria gonorrhea, Neisseria meningitides, Hemophilus influenza, Enterococcus faecalis, Proteus vulgaris, Proteus mirabilis, Helicobacter pylori, Treponema palladium, Borrelia burgdorferi, Borrelia recurrentis, Rickettsial pathogens, Nocardia , and  Acitnomycetes.    
     Fungal infectious agents which can be detected by some embodiments of various aspects described herein can include  Cryptococcus neoformans, Blastomyces dermatitidis, Histoplasma capsulatum, Coccidioides immitis, Paracoccidioides brasiliensis, Candida albicans, Aspergillus fumigautus, Phycomycetes  ( Rhizopus ),  Sporothrix schenckii, Chromomycosis , and  Maduromycosis.    
     Viral infectious agents which can be detected by some embodiments of various aspects described herein can include human immunodeficiency virus, human T-cell lymphocytotrophic virus, hepatitis viruses (e.g., Hepatitis B Virus and Hepatitis C Virus), Epstein-Barr Virus, cytomegalovirus, human papillomaviruses, orthomyxo viruses, paramyxo viruses, adenoviruses, corona viruses, rhabdo viruses, polio viruses, toga viruses, bunya viruses, arena viruses, rubella viruses, and reo viruses. 
     Parasitic agents which can be detected by some embodiments of various aspects described herein can include  Plasmodium falciparum, Plasmodium malaria, Plasmodium vivax, Plasmodium ovale, Onchoverva volvulus, Leishmania, Trypanosoma  spp.,  Schistosoma  spp.,  Entamoeba histolytica, Cryptosporidium, Giardia  spp.,  Trichimonas  spp.,  Balatidium coli, Wuchereria bancrofti, Toxoplasma  spp.,  Enterobius vermicularis, Ascaris lumbricoides, Trichuris trichiura, Dracunculus medinesis, trematodes, Diphyllobothrium latum, Taenia  spp.,  Pneumocystis carinii , and  Necator americanis.    
     In some embodiments, contacting a biological sample with the detection reagents described herein immune-staining, in-situ hybridization or a combination, can be used for the purpose of detecting and identifying pathogens in biological samples. In such embodiments, for example, surface or intracellular antigens, DNA, ribosomal RNA and/or messenger RNA can be detected with some embodiments of the detection reagents and methods described herein. Detection reagents and methods described herein can be especially useful in this context since a) which pathogen may be in the sample is not known in advance, and b) each pathogen cell should respond to one or few of the probes, facilitating the detection reagent and nucleic acid label design. 
     Some embodiments of various aspects described herein can also be used for detection of drug resistance by infectious agents. For example, vancomycin-resistant  Enterococcus faecium , methicillin-resistant  Staphylococcus aureus , penicillin-resistant  Streptococcus pneumoniae , multi-drug resistant  Mycobacterium tuberculosis , and AZT-resistant human immunodeficiency virus can all be identified with some embodiments of various aspects described herein. 
     Thus, the target molecules detected using the compositions and methods described herein can be either patient markers (such as a cancer marker) or markers of infection with a foreign agent, such as bacterial or viral markers. 
     Because of the quantitative nature of detection reagents, the compositions and methods described herein can be used to quantitate target molecules whose abundance is indicative of a biological state or disease condition, for example, blood markers that are upregulated or downregulated as a result of a disease state. 
     In addition, the compositions and methods described herein can be used to provide prognostic information that assists in determining a course of treatment for a patient. For example, the amount of a particular marker for a tumor can be accurately quantified from even a small sample from a patient. For certain diseases like breast cancer, overexpression of certain genes, such as Her2-neu, indicate a more aggressive course of treatment will be needed. 
     In some embodiments, the compositions and methods described herein can be administered to a subject for in vivo diagnosis and/or monitoring of a disease or disorder. Specific devices or methods known in the art for the in vivo detection of fluorescence, e.g., from fluorophores or fluorescent proteins, include, but are not limited to, in vivo near-infrared fluorescence (see, e.g., Frangioni,  Curr. Opin. Chem. Biol,  7:626-634 (2003)), the Maestro™ in vivo fluorescence imaging system (Cambridge Research &amp; Instrumentation, Inc.; Woburn, Mass.), in vivo fluorescence imaging using a flying-spot scanner (see, e.g., Ramanujam et al, IEEE Transactions on Biomedical Engineering, 48:1034-1041 (2001), and the like. Other methods or devices for detecting an optical response include, without limitation, visual inspection, CCD cameras, video cameras, photographic film, laser-scanning devices, fluorometers, photodiodes, quantum counters, epifluorescence microscopes, scanning microscopes, flow cytometers, fluorescence microplate readers, or signal amplification using photomultiplier tubes. 
     Any device or method known in the art for detecting the radioactive emissions of radionuclides in a subject is suitable for use in various aspects described herein. For example, methods such as Single Photon Emission Computerized Tomography (SPECT), which detects the radiation from a single photon gamma-emitting radionuclide using a rotating gamma camera, and radionuclide scintigraphy, which obtains an image or series of sequential images of the distribution of a radionuclide in tissues, organs, or body systems using a scintillation gamma camera, may be used for detecting the radiation emitted from a radiolabeled aggregate. Positron emission tomography (PET) is another suitable technique for detecting radiation in a subject. 
     Analysis of Pathology Samples: 
     RNA extracted from formaldehyde- or paraformaldehyde-fixed paraffin-embedded tissue samples is typically poor in quality (fragmented) and low in yield. This makes gene expression analysis of low-expressing genes in histology samples or archival pathology tissues extremely difficult and often completely infeasible. The detection reagents and methods described herein can fill this unmet need by allowing the analysis of very small quantities of low-quality total RNA. 
     To use detection reagents in such an application, total RNA can be extracted from formaldehyde- or paraformaldehyde-fixed paraffin-embedded tissue samples (or similar) using commercially available kits such as RecoverAll Total Nucleic Acid Isolation Kit (Ambion) following manufacturer&#39;s protocols. RNA in such samples is frequently degraded to small fragments (200 to 500 nucleotides in length), and many paraffin-embedded histology samples only yield tens of nanograms of total RNA. Small amounts (5 to 100 ng) of this fragmented total RNA can be used directly as target analyte upon contact with the detection reagents described herein, using the methods described herein described herein. 
     Screening Methods: 
     The methods described herein can be used, among other things, for determining the effect of a perturbation, including chemical compounds, mutations, temperature changes, growth hormones, growth factors, disease, or a change in culture conditions, on various target molecules, thereby identifying target molecules whose presence, absence or levels are indicative of particular biological states. In one embodiment, some aspects described herein can be used to elucidate and discover components and pathways of disease states. For example, the comparison of quantities of target molecules present in a disease tissue with “normal” tissue allows the elucidation of important target molecules involved in the disease, thereby identifying targets for the discovery/screening of new drug candidates that can be used to treat disease. 
     Targeted Delivery Vehicles: 
     In some embodiments, the therapeutic and/or diagnostic agent can be encapsulated within the particles that provide conjugation sites for the probe reagents and nucleic acid labels. In such embodiments, the detection reagents and methods described herein can be used to deliver a therapeutic and/or diagnostic agent to cells where the probe reagents of the detection reagents bind. Nucleic acid labels of the detection reagents can be detected to monitor the location of drug administration. 
     Cell Lineage Tracking: 
     In some embodiments, the detection reagents described herein can be used to track cell lineage, e.g., in culture or in vivo. For example, the probe reagents of the detection reagents can bind to live cells of interest, allowing labeling and/or tracking of individual cell differentiation. Examples of such application include, but are not limited to, lineage tracking in stem cell differentiation, and lineage determination of dendritic cells and/or white blood cells. In some embodiments, these cells after lineage determination can be further used accordingly. 
     Kits Comprising Detection Reagents 
     Kits for various assays are also provided herein. In some embodiments, a kit can comprise: (a) a plurality of nucleic acid labels of the detection reagents described herein; and (b) at least one coupling reagent required to conjugate the nucleic acid labels to probe reagents of interest. In such embodiments, users can attach the provided nucleic acid labels to their probe reagents of interest to form their own detection reagents described herein. Examples of the coupling reagent required for nucleic acid label-probe reagent conjugation can include any reagents that are generally used to perform any of the conjugation methods described herein, e.g., biotin and avidin-like molecules such as streptavidin or neutravidin. However, in alternative embodiments, the kit can comprise a plurality of the detection reagents described herein that are ready for use and thus no nucleic acid label-probe reagent conjugation steps are required to be performed by users prior to use. 
     In some embodiments, the kit can further comprise at least one reagent, e.g., used in a readout method described herein. For example, if the readout method is sequencing-based, the kit can further comprise at least one agent used in sequencing-based readout. Alternatively, if the readout method is hybridization-based, the kit can further comprise at least one set of decoder probes complementary to at least a portion of subsequences of the detection reagents, wherein each subpopulation of the decoder probes comprises a different detectable label, each different detectable label producing a different signal signature. 
     Accordingly, in some embodiments, a kit for hybridization-based readout can comprise: (a) a plurality of nucleic acid labels of the detection reagents described herein; (b) at least one reagent required to conjugate the nucleic acid labels to probe reagents of interest; and (c) at least one set of decoder probes complementary to at least a portion of subsequences of the detection reagents, wherein each subpopulation of the decoder probes comprises a different detectable label, each different detectable label producing a different signal signature. In some embodiments, the kit can further comprise at least one reagent, e.g., used in the readout method. 
     In alternative embodiments, a kit for hybridization-based readout can comprise: (a) a plurality of the detection reagents described herein; (b) at least one set of decoder probes complementary to at least a portion of subsequences of the detection reagents, wherein each subpopulation of the decoder probes comprises a different detectable label, each different detectable label producing a different signal signature; and (c) at least one reagent. 
     In any embodiments of the kit described herein, the plurality of the detection reagents can include one or more different kinds of the detection reagents. In some embodiments, it is desirable to provide different kinds of the detection reagents (e.g., different types of probe reagents, target binding domains, and/or target analytes) in separate containers. The number of different kinds of the detection reagents provided in the kit can be tailored for each application described herein. In some embodiments, the kit can comprise at least 2, at least 3, at least 4, at least 5, at least 6 at least 7, at least 8, at least 9, at least 10, at least 20, at least 30, at least 40, at least 50, at least 60, at least 70, at least 80, at least 90, at least 100 or more different kinds of the detection reagents. 
     In any embodiments of the kit described herein, the kit can comprise a plurality of sets of decoder probes, e.g., e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10 or more sets of decoder probes, wherein each set of decoder probes can target a different pre-determined sequence of the nucleic acid label. In each set of the decoder probes, there can be about 2, 3, 4, 5, 6, 7, 8, 9, 10 or more distinct populations of decoder probes. The decoder probes can be pre-labeled with at least one detectable label or unlabeled. In some embodiments where the decoder probes are not pre-labeled, the kit can further comprise one or more distinct detectable labels provided in separate containers for labeling the decoder probes. In some embodiments, the detectable label can be an optical label described herein. 
     Examples of a reagent, e.g., used in a readout method, can include, but are not limited to, a readout reagent, a wash buffer, a signal removal buffer, buffers for performing hybridization reactions, restriction endonucleases, nucleic acid ligases, and any combinations thereof. 
     In some embodiments, the detection reagents can be provided in a solution phase. In other embodiments, the detection reagents can be immobilized in a solid support or substrate. 
     By “substrate” or “solid support” or other grammatical equivalents herein is meant any material that can be modified to contain discrete individual sites appropriate for the attachment or association of beads and is amenable to at least one detection method. As will be appreciated by those in the art, the number of possible substrates is very large. Possible substrates include, but are not limited to, glass and modified or functionalized glass, plastics (including acrylics, polystyrene and copolymers of styrene and other materials, polypropylene, polyethylene, polybutylene, polyurethanes, Teflon, etc.), polysaccharides, nylon or nitrocellulose, resins, silica or silica-based materials including silicon and modified silicon, carbon, metals, inorganic glasses, plastics, optical fiber bundles, and a variety of other polymers. In general, the substrates allow optical detection and do not themselves appreciably fluoresce. 
     Generally the substrate is flat (planar), although as will be appreciated by those in the art, other configurations of substrates may be used as well; for example, three dimensional configurations can be used, for example by embedding the detection reagents in a porous block of plastic that allows sample access to the detection reagents and using a confocal microscope for detection. In some embodiments, the detection reagents can be placed on the inside surface of a tube, for flow-through sample analysis to minimize sample volume. Preferred substrates include optical fiber bundles, and flat planar substrates such as glass, polystyrene and other plastics and acrylics. In some embodiment, the solid support or substrate can be a multi-well plate. 
     In addition to the above mentioned components, the kit can include informational material. The informational material can be descriptive, instructional, marketing or other material that relates to the methods described herein and/or the use of the aggregates for the methods described herein. For example, the informational material describes methods for administering the detection reagents to a subject, and/or includes instructions to label decoder probes with detectable labels provided therein and/or instructions to conjugate at least one nucleic acid label to a probe reagent. The kit can also include a delivery device. 
     In some embodiments, the informational material can include instructions to administer the formulation in a suitable manner, e.g., in a suitable dose, dosage form, or mode of administration (e.g., a dose, dosage form, or mode of administration described herein). In another embodiment, the informational material can include instructions for identifying a suitable subject, e.g., a human, e.g., an adult human. The informational material of the kits is not limited in its form. In many cases, the informational material, e.g., instructions, is provided in printed matter, e.g., a printed text, drawing, and/or photograph, e.g., a label or printed sheet. However, the informational material can also be provided in other formats, such as Braille, computer readable material, video recording, or audio recording. In another embodiment, the informational material of the kit is a link or contact information, e.g., a physical address, email address, hyperlink, website, or telephone number, where a user of the kit can obtain substantive information about the formulation and/or its use in the methods described herein. Of course, the informational material can also be provided in any combination of formats. 
     In some embodiments, the kit contains separate containers, dividers or compartments for each component and informational material. For example, each different component can be contained in a bottle, vial, or syringe, and the informational material can be contained in a plastic sleeve or packet. In other embodiments, the separate elements of the kit are contained within a single, undivided container. For example, the formulation is contained in a bottle, vial or syringe that has attached thereto the informational material in the form of a label. 
     In some embodiments, the kit includes a plurality, e.g., a pack, of individual containers, each containing one or more unit dosage forms of the composition comprising the detection reagents. For example, the kit includes a plurality of syringes, ampules, foil packets, or blister packs, each containing a single unit dose of the formulation. The containers of the kits can be air tight and/or waterproof. 
     Embodiments of the various aspects described herein can be illustrated by the following numbered paragraphs. 
     1. A method for detecting a plurality of analytes in a sample, comprising: 
     a. contacting the sample with a composition comprising a plurality of detection reagents, wherein each subpopulation of the detection reagents targets at least one different analyte, and wherein each detection reagent comprises: 
     at least one probe reagent targeting an analyte and at least one nucleic acid label comprising one or a plurality of pre-determined subsequences, wherein said at least one probe reagent and said at least one nucleic acid label are conjugated together; and wherein at least a portion of said one or the plurality of pre-determined subsequences form an identifier of said at least one probe reagent; and 
     b. detecting in a temporally-sequential manner said one or the plurality of the pre-determined subsequences of said detection reagent, wherein said detection of the subsequences each generates a signal signature corresponding to said subsequence, and wherein a temporal order of the signal signatures corresponding to said one or the plurality of the subsequences of said detection reagent identifies a subpopulation of the detection reagents. 
     2. The method of paragraph 1, wherein said each subpopulation of the detection reagents targets a set of analytes (e.g., at least two analytes or more). 
     3. The method of paragraph 1 or 2, wherein the temporal order of the signal signatures corresponding to said one or the plurality of the subsequences of said detection reagent is unique for each subpopulation of the detection reagents. 
     4. The method of any of paragraphs 1-3, wherein said detection reagents are present in a soluble phase. 
     5. The method of any of paragraphs 1-4, further comprising processing said sample before said contacting with said plurality of detection reagents. 
     6. The method of any of paragraphs 1-5, further comprising removing any unbound detection reagents before the detecting step (b). 
     7. The method of any of paragraphs 1-6, further comprising comparing said temporal order of the signal signatures with different identifiers of said at least one probe reagent, wherein an agreement between the temporal order of the signal signatures and a particular identifier of said at least one probe reagent identifies the analyte in the sample. 
     8. The method of any of paragraphs 1-7, further comprising measuring the intensity of the signal signatures generated from each subpopulation of the detection reagents. 
     9. The method of paragraph 8, wherein the intensity of the signal signatures generated from each subpopulation of the detection reagents indicates an amount of the analyte. 
     10. The method of paragraph 8 or 9, wherein the intensity of the signal signatures generated from each subpopulation of the detection reagents is used in identification of the subpopulation of the detection reagents. 
     11. The method of any of paragraphs 1-10, wherein said detecting of step (b) comprises sequencing. 
     12. The method of paragraph 11, wherein said sequencing is performed via ligation, hybridization, synthesis, amplification, or single-base extension. 
     13. The method of any of paragraphs 1-12 wherein said detecting of step (b) comprises hybridizing a decoder probe with said subsequence, wherein said decoder probe comprises a detectable label. 
     14. The method of any of paragraphs 1-13, wherein said detecting of step (b) comprises: 
     a. hybridizing a set of decoder probes with a subsequence of the detection reagents, wherein each subpopulation of the decoder probes comprises a detectable label, each detectable label producing a signal signature; 
     b. detecting said signal signature produced by the hybridization of said set of decoder probes; 
     c. optionally removing said different signal signature produced by the hybridization of said set of decoder probes; and 
     d. repeating steps (a) through (c) for other subsequences of said detection reagents, thereby producing a temporal order of the signal signatures corresponding to said each detection reagent. 
     15. The method of paragraph 14, wherein said each subpopulation of the decoder probes comprises a different detectable label, each different detectable label producing a different signal signature. 
     16. The method of paragraph 14 or 15, wherein said each subpopulation of the decoder probes is at least partially or completely complementary to said subsequence of the detection reagents. 
     17. The method of any of paragraphs 14-16, wherein at least two or more subpopulations of the decoder probes are at least partially or completely complementary to the same subsequence of the detection reagents. 
     18. The method of any of paragraphs 14-17, wherein said removing step is performed by washing, heating, photobleaching, displacement, cleavage, enzymatic digestion, quenching, chemical degradation, bleaching, oxidation or any combinations thereof. 
     19. The method of any of paragraphs 14-18, wherein said detectable label comprises or is an optical label selected from the group consisting of a small-molecule dye, a fluorescent molecule, a fluorescent protein, a quantum dot, Raman label, a chromophore, and any combinations thereof. 
     20. The method of any of paragraphs 14-19, wherein said detectable label comprises or is a colorimetric reagent. 
     21. The method of any of paragraphs 14-20, wherein said detectable label comprises or is a Raman label. 
     22. The method of any of paragraphs 1-21, wherein said signal signatures comprise or are optical signatures. 
     23. The method of paragraph 22, wherein said optical signatures comprise signatures of fluorescent color, visible light, no-color, Raman label, or any combinations thereof. 
     24. The method of paragraph 22, wherein said optical signatures comprise signatures of one or more fluorescent colors, one or more visible lights, one or more no-colors, one or more Raman labels, or any combinations thereof. 
     25. The method of any of paragraphs 22-24, wherein said optical signatures are detected by optical imaging or spectroscopy. 
     26. The method of any of paragraphs 1-25, wherein said analytes are selected from the group consisting of antigens, receptors, proteins, peptides, sugars, glycoproteins, peptidoglycans, lipids, nucleic acids, oligonucleotides, cells, viruses, and any combinations thereof. 
     27. The method of any of paragraphs 1-26, wherein said nucleic acids are selected from the group consisting of cellular DNA or RNA, messenger RNA, microRNA, ribosomal RNA, and any combinations thereof. 
     28. The method of any of paragraphs 1-27, wherein said sample is a protein sample immobilized on a solid support. 
     29. The method of paragraph 28, wherein the solid support is a blotting membrane. 
     30. The method of any of paragraphs 1-27, wherein said sample is a biological sample. 
     31. The method of paragraph 30, wherein said biological sample comprises one or more cells, one or more tissues, one or more fluids or any combinations thereof. 
     32. The method of paragraph 30 or 31, wherein said biological sample comprises blood, sputum, cerebrospinal fluid, urine, saliva, sperm, sweat, mucus, nasal discharge, vaginal fluids or any combinations thereof. 
     33. The method of any of paragraphs 30-31, wherein the said biological sample comprises a biopsy, a surgically removed tissue, a swap or any combinations thereof. 
     34. The method of paragraphs 1-27, wherein said sample comprises an environmental sample, food, food byproduct, soil, an archaeological sample, an extraterrestrial sample, or any combinations thereof. 
     35. The method of any of paragraphs 1-34, wherein said at least one probe reagent and said at least one nucleic acid label are conjugated together by at least one linker. 
     36. The method of paragraph 35, wherein said linker is a bond. 
     37. The method of paragraph 35 or 36, wherein said linker is a linker molecule. 
     38. The method of paragraph 37, wherein said linker molecule is a polymer, sugar, nucleic acid, peptide, protein, hydrocarbon, lipid, polyethylene glycol, crosslinker, or any combinations thereof. 
     39. The method of any of paragraphs 35-38, wherein said linker is a particle. 
     40. The method of paragraph 39, wherein said particle is selected from a group consisting of a gold nanoparticle, a magnetic bead or nanoparticle, a polystyrene bead, a nanotube, a nanowire, a microparticle, and any combinations thereof. 
     41. The method of paragraph 40, wherein said particle is a nanoparticle. 
     42. The method of any of paragraphs 39-41, wherein said particle is modified. 
     43. The method of any of paragraphs 39-42, wherein said particle is coated with streptavidin or a derivative thereof. 
     44. The method of any of paragraphs 39-43, wherein said particle is modified with at least one functional group. 
     45. The method of paragraph 44, wherein said at least one functional group is selected from the group consisting of amine, carboxyl, hydroxyl, aldehyde, ketone, tosyl, silanol, chlorine, hydrazine, hydrazide, photoreactive groups, and any combinations thereof. 
     46. The method of any of paragraphs 35-45, wherein said linker is multivalent. 
     47. The method of paragraph 46, wherein when the multivalent linker is an avidin-like molecule, both the probe reagent and the nucleic acid label are biotinylated. 
     48. The method of any of paragraphs 1-47, wherein said at least one probe reagent is selected from the group consisting of a nucleic acid, an antibody or a portion thereof, an antibody-like molecule, an enzyme, a cell, an antigen, a small molecule, a protein, a peptide, a peptidomimetic, a sugar, a carbohydrate, a lipid, a glycan, a glycoprotein, an aptamer, and any combinations thereof. 
     49. The method of any of paragraphs 1-48, wherein said at least one probe reagent is modified. 
     50. The method of any of paragraphs 1-49, wherein said at least one probe reagent is biotinylated. 
     51. The method of any of paragraphs 1-50, wherein said at least one nucleic acid label is single-stranded, double-stranded, partially double-stranded, a hairpin, linear, circular, branched, a concatemer, or any combinations thereof. 
     52. The method of any of paragraphs 1-51, wherein said at least one nucleic acid label is modified. 
     53. The method of any of paragraphs 1-52, wherein said at least one nucleic acid label is designed for minimal cross-hybridization of bases with each other. 
     54. The method of any of paragraphs 1-53, wherein said at least one nucleic acid label is conjugated to at least one detectable molecule. 
     55. The method of paragraph 54, wherein said at least one detectable molecule is an optical molecule selected from the group consisting of a small-molecule dye, a fluorescent protein, a quantum dot, a Raman label, a chromophore, and any combinations thereof. 
     56. The method of any of paragraphs 1-55, wherein each of said plurality of the pre-determined subsequences comprises at least one base. 
     57. The method of any of paragraphs 1-56, wherein each of said plurality of the pre-determined subsequences comprises from 1 to 100 nucleobases. 
     58. The method of any of paragraphs 1-57, wherein said plurality of the pre-determined subsequences are conjugated together by at least one sequence linker. 
     59. The method of paragraph 58, wherein said sequence linker is a bond. 
     60. The method of any of paragraphs 58-59, wherein said sequence linker is a nucleotidic linker. 
     61. The method of paragraph 60, wherein said nucleotidic linker is single-stranded, double-stranded, partially double-stranded, a hairpin or any combinations thereof. 
     62. The method of paragraph 60 or 61, wherein said nucleotidic linker is at least one nucleotide long. 
     63. The method of any of paragraphs 1-62, wherein said detection reagent comprises one probe reagent and a plurality of nucleic acid labels. 
     64. The method of any of paragraphs 1-62, wherein said detection reagent comprises a plurality of probe reagents and a nucleic acid label. 
     65. The method of any of paragraphs 1-62, wherein said detection reagent comprises a plurality of probe reagents and a plurality of nucleic acid labels. 
     66. The method of any of paragraphs 1-65, wherein the method is adapted for use in immunofluorescence. 
     67. The method of any of paragraphs 1-66, wherein the method is adapted for use in immunohistochemistry. 
     68. The method of any of paragraphs 1-67, wherein the method is adapted for use in fluorescence in situ hybridization. 
     69. The method of any of paragraphs 1-68, wherein the method is adapted for use in western blot. 
     70. A detection reagent comprising at least one probe reagent and at least one nucleic acid label, wherein said at least one nucleic acid label comprises at least one pre-determined subsequence to be detected in a temporally-sequential manner; 
     wherein said at least one pre-determined subsequence forms an identifier of said at least one probe reagent; and 
     wherein said at least one probe reagent and said at least one nucleic acid label are conjugated together. 
     71. The detection reagent of paragraph 70, wherein the detection reagent is present in a soluble phase. 
     72. The detection reagent of paragraph 70 or 71, wherein said at least one probe reagent and said at least one nucleic acid label are conjugated together by at least one linker. 
     73. The detection reagent of paragraph 72, wherein said linker is a bond. 
     74. The detection reagent of paragraph 72 or 73, wherein said linker is a linker molecule. 
     75. The detection reagent of paragraph 74, wherein said linker molecule is a polymer, sugar, nucleic acid, peptide, protein, hydrocarbon, lipid, polyethelyne glycol, crosslinker or combination thereof. 
     76. The detection reagent of any of paragraphs 72-75, wherein said linker is a particle. 
     77. The detection reagent of paragraph 76, wherein said particle is selected from a group consisting of a gold nanoparticle, a magnetic bead or nanoparticle, a polystyrene bead, a nanotube, a nanowire, a microparticle, and any combinations thereof. 
     78. The detection reagent of paragraph 76 or 77, wherein said particle is a nanoparticle. 
     79. The detection reagent of any of paragraphs 76-78, wherein said particle is modified. 
     80. The detection reagent of any of paragraphs 76-79, wherein said particle is coated with streptavidin or a derivative thereof. 
     81. The detection reagent of any of paragraphs 76-80, wherein said particle is modified with at least one functional group. 
     82. The detection reagent of paragraph 81, wherein the at least one functional group is selected from the group consisting of amine, carboxyl, hydroxyl, aldehyde, ketone, tosyl, silanol, chlorine, hydrazine, hydrazide, photoreactive groups, and any combinations thereof. 
     83. The detection reagent of any of paragraphs 72-82, wherein said linker is multivalent. 
     84. The detection reagent of paragraph 83, wherein when the multivalent linker is an avidin-like molecule, both the probe reagent and the nucleic acid label are biotinylated. 
     85. The detection reagent of any of paragraphs 70-84, wherein said at least one probe reagent is selected from the group consisting of a nucleic acid, an antibody or a portion thereof, an antibody-like molecule, an enzyme, a cell, an antigen, a small molecule, a protein, a peptide, a peptidomimetic, a sugar, a carbohydrate, a lipid, a glycan, a glycoprotein, an aptamer, and any combinations thereof. 
     86. The detection reagent of any of paragraphs 70-85, wherein said at least one probe reagent is modified. 
     87. The detection reagent of any of paragraphs 70-86, wherein said at least one probe reagent is biotinylated. 
     88. The detection reagent of any of paragraphs 70-87, wherein said at least one nucleic acid label is single-stranded, double-stranded, partially double-stranded, a hairpin, linear, circular, branched, a concatemer, or any combinations thereof. 
     89. The detection reagent of any of paragraphs 70-88, wherein said at least one nucleic acid label is modified. 
     90. The detection reagent of any of paragraphs 70-89, wherein said at least one nucleic acid label is designed for minimal cross-hybridization of bases with each other. 
     91. The detection reagent of any of paragraphs 70-90, wherein said at least one nucleic acid label is conjugated to at least one detectable molecule. 
     92. The detection reagent of paragraph 91, wherein said at least one detectable molecule is an optical molecule selected from the group consisting of small-molecule dye, a fluorescent protein, a quantum dot, a Raman label, a chromophore, and any combinations thereof. 
     93. The detection reagent of any of paragraphs 70-92, wherein said at least one nucleic acid label comprises a plurality of pre-determined subsequences. 
     94. The detection reagent of any of paragraphs 70-93, wherein each of said plurality of predetermined subsequences comprises at least one base. 
     95. The detection reagent of any of paragraphs 70-94, wherein each of said plurality of predetermined subsequences comprises from 1 to 100 nucleobases. 
     96. The detection reagent of any of paragraphs 70-95, wherein said plurality of the pre-determined subsequences are conjugated together by at least one sequence linker. 
     97. The detection reagent of paragraph 96, wherein said sequence linker is a bond. 
     98. The detection reagent of any of paragraphs 96-97, wherein said sequence linker is a nucleotidic linker. 
     99. The detection reagent of paragraph 98, wherein said nucleotidic linker is single-stranded, double-stranded, partially double-stranded, a hairpin, or any combinations thereof. 
     100. The detection reagent of paragraph 98 or 99, wherein said nucleotidic linker is at least one nucleotide long. 
     101. The detection reagent of any of paragraphs 70-100, wherein said detection reagent comprises one probe reagent and a plurality of nucleic acid labels. 
     102. The detection reagent of any of paragraphs 70-101, wherein said detection reagent comprises a plurality of probe reagents and a nucleic acid label. 
     103. The detection reagent of any of paragraphs 70-102, wherein said detection reagent comprises a plurality of probe reagents and a plurality of nucleic acid labels. 
     104. The detection reagent of any of paragraphs 70-103, wherein the detection reagent is adapted for use in immunofluorescence. 
     105. The detection reagent of any of paragraphs 70-104, wherein the detection reagent is adapted for use in immunohistochemistry. 
     106. The detection reagent of any of paragraphs 70-105, wherein the detection reagent is adapted for use in fluorescence in situ hybridization. 
     107. The detection reagent of any of paragraphs 70-106, wherein the detection reagent is adapted for use in western blot. 
     108. A kit comprising: 
     a. a plurality of the detection reagents of any of paragraphs 70-107; and 
     b. at least one reagent. 
     109. The kit of paragraph 108, wherein the kit further comprises at least one set of decoder probes complementary to at least a portion of subsequences of the detection reagents, wherein each subpopulation of the decoder probes comprises a different detectable label, each different detectable label producing a different signal signature. 
     110. The kit of paragraph 108 or 109, wherein said detection reagents are present in a soluble phase. 
     111. The kit of any of paragraphs 108-110, wherein said detection reagents are immobilized in a multi-well plate. 
     112. The kit of any of paragraphs 108-111, wherein said at least one reagent is selected from the group consisting of a readout reagent, a wash buffer, a signal removal buffer, and any combinations thereof. 
     113. A kit comprising: 
     a. a plurality of the nucleic acid labels of the detection reagents of any of paragraphs 70-107; 
     b. at least one coupling agent that allows a user to conjugate the nucleic acid labels to the user&#39;s probe reagents of interest, thereby forming the detection reagents comprising the user&#39;s probe reagents of interest; and 
     c. at least one reagent. 
     114. The kit of paragraph 113, wherein the kit further comprises at least one set of decoder probes complementary to at least a portion of subsequences of the detection reagents, wherein each subpopulation of the decoder probes comprises a different detectable label, each different detectable label producing a different signal signature. 
     115. The kit of paragraph 113 or 114, wherein the detection reagents comprising the user&#39;s probe reagents of interest are present in a soluble phase. 
     116. The kit of any of paragraphs 113-115, wherein the detection reagents comprising the user&#39;s probe reagents of interest are immobilized in a multi-well plate. 
     117. The kit of any of paragraphs 113-116, wherein said at least one reagent is selected from the group consisting of a readout reagent, a wash buffer, a signal removal buffer, and any combinations thereof. 
     Some Selected Definitions 
     Unless stated otherwise, or implicit from context, the following terms and phrases include the meanings provided below. Unless explicitly stated otherwise, or apparent from context, the terms and phrases below do not exclude the meaning that the term or phrase has acquired in the art to which it pertains. The definitions are provided to aid in describing particular embodiments of the aspects described herein, and are not intended to limit the claimed invention, because the scope of the invention is limited only by the claims. Further, unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular. 
     As used herein the term “comprising” or “comprises” is used in reference to compositions, methods, and respective component(s) thereof, that are essential to the invention, yet open to the inclusion of unspecified elements, whether essential or not. Additionally, the term “comprising” or “comprises” includes “consisting essentially of and “consisting of” 
     As used herein the term “consisting essentially of” refers to those elements required for a given embodiment. The term permits the presence of additional elements that do not materially affect the basic and novel or functional characteristic(s) of that embodiment of the invention. 
     The term “consisting of” refers to compositions, methods, and respective components thereof as described herein, which are exclusive of any element not recited in that description of the embodiment. 
     Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used herein should be understood as modified in all instances by the term “about.” The term “about” when used in connection with percentages can mean±1%. 
     The singular terms “a,” “an,” and “the” include plural referents unless context clearly indicates otherwise. Similarly, the word “or” is intended to include “and” unless the context clearly indicates otherwise. 
     Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of this disclosure, suitable methods and materials are described below. The term “comprises” means “includes.” The abbreviation, “e.g.” is derived from the Latin exempli gratia, and is used herein to indicate a non-limiting example. Thus, the abbreviation “e.g.” is synonymous with the term “for example.” 
     As used herein, the term “identifier” generally refers to a unique expression to distinguish variations from one to another among a class of substances, items, or objects. In particular embodiments, the term “identifier” as used herein refers to association of a unique pre-determined subsequence to a specific probe reagent, thus conferring the presence and identity of the probe reagent when the pre-determined subsequence is detected. 
     The term “statistically significant” or “significantly” refers to statistical significance and generally means a two standard deviation (2SD) above or below a reference level. The term refers to statistical evidence that there is a difference. It is defined as the probability of making a decision to reject the null hypothesis when the null hypothesis is actually true. The decision is often made using the p-value. 
     As used herein, the term “substantially” means a proportion of at least about 60%, or preferably at least about 70% or at least about 80%, or at least about 90%, at least about 95%, at least about 97% or at least about 99% or more, or any integer between 70% and 100%. In some embodiments, the term “substantially” means a proportion of at least about 90%, at least about 95%, at least about 98%, at least about 99% or more, or any integer between 90% and 100%. In some embodiments, the term “substantially” can include 100%. 
     The term “sphere” means a particle having an aspect ratio of at most 3:1. The term “aspect ratio” means the ratio of the longest axis of an object to the shortest axis of the object, where the axes are not necessarily perpendicular. 
     The term “rod” means a particle having a longest dimension of at most 5000 nm, and having an aspect ratio of from 3:1 to 20:1. 
     The term “prism” means a particle having at least two non-parallel faces connected by a common edge. 
     As used herein, the term “pharmaceutically acceptable carrier” refers to a pharmaceutically-acceptable material, composition or vehicle for administration of the detection reagents. Pharmaceutically acceptable carriers include any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents, and the like which are compatible with the activity of the detection reagents and are physiologically acceptable to the subject. Some examples of materials which can serve as pharmaceutically-acceptable carriers include: (1) sugars, such as lactose, glucose and sucrose; (2) starches, such as corn starch and potato starch; (3) cellulose, and its derivatives, such as sodium carboxymethyl cellulose, methylcellulose, ethyl cellulose, microcrystalline cellulose and cellulose acetate; (4) powdered tragacanth; (5) malt; (6) gelatin; (7) lubricating agents, such as magnesium stearate, sodium lauryl sulfate and talc; (8) excipients, such as cocoa butter and suppository waxes; (9) oils, such as peanut oil, cottonseed oil, safflower oil, sesame oil, olive oil, corn oil and soybean oil; (10) glycols, such as propylene glycol; (11) polyols, such as glycerin, sorbitol, mannitol and polyethylene glycol (PEG); (12) esters, such as ethyl oleate and ethyl laurate; (13) agar; (14) buffering agents, such as magnesium hydroxide and aluminum hydroxide; (15) alginic acid; (16) pyrogen-free water; (17) isotonic saline; (18) Ringer&#39;s solution; (19) ethyl alcohol; (20) pH buffered solutions; (21) polyesters, polycarbonates and/or polyanhydrides; (22) bulking agents, such as polypeptides and amino acids (23) serum component, such as serum albumin, HDL and LDL; (22) C2-C12 alchols, such as ethanol; and (23) other non-toxic compatible substances employed in pharmaceutical formulations. Wetting agents, coloring agents, release agents, coating agents, sweetening agents, flavoring agents, perfuming agents, preservative and antioxidants can also be present in the formulation. The terms such as “excipient”, “carrier”, “pharmaceutically acceptable carrier” are used interchangeably herein. 
     As used here, the term “pharmaceutically acceptable” refers to those compounds, materials, compositions, and/or dosage forms which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of human beings and animals without excessive toxicity, irritation, allergic response, or other problem or complication, commensurate with a reasonable benefit/risk ratio. 
     As used herein, the term “therapeutic agent” refers to a biological or chemical agent used for treatment, curing, mitigating, or preventing deleterious conditions in a subject. The term “therapeutic agent” also includes substances and agents for combating a disease, condition, or disorder of a subject, and includes drugs, diagnostics, and instrumentation. “Therapeutic agent” also includes anything used in medical diagnosis, or in restoring, correcting, or modifying physiological functions. The terms “therapeutic agent” and “pharmaceutically active agent” are used interchangeably herein. 
     A therapeutic agent can be selected according to the treatment objective and biological action desired. Thus, a therapeutic agent can be selected from any class suitable for the therapeutic objective. Further, the therapeutic agent may be selected or arranged to provide therapeutic activity over a period of time. 
     Exemplary pharmaceutically active compound include, but are not limited to, those found in Harrison&#39;s Principles of Internal Medicine, 13th Edition, Eds. T. R. Harrison McGraw-Hill N.Y., NY; Physicians Desk Reference, 50th Edition, 1997, Oradell New Jersey, Medical Economics Co.; Pharmacological Basis of Therapeutics, 8th Edition, Goodman and Gilman, 1990; United States Pharmacopeia, The National Formulary, USP XII NF XVII, 1990; current edition of Goodman and Oilman&#39;s The Pharmacological Basis of Therapeutics; and current edition of The Merck Index, the complete content of all of which are herein incorporated in its entirety. 
     Exemplary pharmaceutically active agents include, but are not limited to, steroids and nonsteroidal anti-inflammatory agents, antirestenotic drugs, antimicrobial agents, angiogenic factors, calcium channel blockers, thrombolytic agents, antihypertensive agents, anti-coagulants, antiarrhythmic agents, cardiac glycosides, and the like. 
     In some embodiments, the therapeutic agent is selected from the group consisting of salicylic acid and derivatives (aspirin), para-aminophenol and derivatives (acetaminophen), arylpropionic acids (ibuprofen), corticosteroids, histamine receptor antagonists and bradykinin receptor antagonists, leukotriene receptor antagonists, prostaglandin receptor antagonists, platelet activating factor receptor antagonists, sulfonamides, trimethoprim-sulfamethoxazole, quinolones, penicillins, cephalosporin, basic fibroblast growth factor (FGF), acidic fibroblast growth factor, vascular endothelial growth factor, angiogenic transforming growth factor alpha and beta, tumor necrosis factor, angiopoietin, platelet-derived growth factor, dihydropyridines (e.g., nifedipine, benzothiazepines such as dilitazem, and phenylalkylamines such as verapamil), urokinase plasminogen activator, urokinase, streptokinase, angiotensin converting enzyme (ACE) inhibitors, spironolactone, tissue plasminogen activator (tPA), diuretics, thiazides, antiadrenergic agents, clonidine, propanolol, angiotensin-converting enzyme inhibitors, captopril, angiotensin receptor antagonists, losartan, calcium channel antagonists, nifedine, heparin, warfarin, hirudin, tick anti-coagulant peptide, and low molecular weight heparins such as enoxaparin, lidocaine, procainamide, encainide, flecanide, beta adrenergic blockers, propranolol, amiodarone, verpamil, diltiazem, nickel chloride, cardiac glycosides, angiotensin converting enzyme inhibitors, angiotensin receptor antagonists, nitrovasodilators, hypolipidemic agents (e.g., nicotinic acid, probucol, etc.), bile acid-binding resins (e.g., cholestyramine, and fibric acid derivatives e.g., clofibrate), HMG CoA reductase inhibitors, HMG CoA synthase inhibitors, squalene synthase inhibitors, squalene epoxidase inhibitors, statins (e.g., lovastatin, cerivastatin, fluvastatin, pravastatin, simvaststin, etc.), anti-psychotics, SSRIs, antiseizure medication, contraceptives, systemic and local analgesics (chronic pain, bone growth/remodeling factors (osteoblast/osteoclast recruiting and stimulating factors), neurotransmitters (L-DOPA, Dopamine, neuropeptides), emphysema drugs, TGF-beta), rapamycin, naloxone, paclitaxel, amphotericin, Dexamethasone, flutamide, vancomycin, phenobarbital, cimetidine, atenolol, aminoglycosides, hormones (e.g., thyrotropin-releasing hormone, p-nitrophenyl beta-cellopentaosideand luteinizing hormone-releasing hormone), vincristine, amiloride, digoxin, morphine, procainamide, quinidine, quinine, ranitidine, triamterene, trimethoprim, vancomycin, aminoglycosides, and penicillin, and pharmaceutically acceptable salts thereof. 
     As used herein, the term “fluorescent color” refers to a color emitted by any fluorophore (e.g., fluorescent dye, fluorescent particles such as quantum dots, and/or fluorescent proteins) upon light excitation and/or electromagnetic radiation. Fluorescent dye as disclosed herein refers to a dye which exhibits energy and is visible under illumination at a predefined wavelength. Numerous fluorescent molecules are commercially available and can be adapted for use in the methods, detection reagents and kits as disclosed herein, and include those from Molecular Probes, Sigma and similar other commercial sources. In some embodiments, a “fluorescent color” can be produced by phosphorescence. In some embodiments, a “fluorescent color” can be produced by luminescence (including bioluminescence). 
     To the extent not already indicated, it will be understood by those of ordinary skill in the art that any one of the various embodiments herein described and illustrated may be further modified to incorporate features shown in any of the other embodiments disclosed herein. 
     The following examples illustrate some embodiments and aspects of the invention. It will be apparent to those skilled in the relevant art that various modifications, additions, substitutions, and the like can be performed without altering the spirit or scope of the invention, and such modifications and variations are encompassed within the scope of the invention as defined in the claims which follow. The following examples do not in any way limit the invention. 
     EXAMPLES 
     Example 1: Exemplary Hybridization-Based Detection Methods of Detection Reagents 
     A solution suspension of streptavidin-coated Dynabeads (of about 1 μm), each conjugated to one of six nucleic acid labels and a corresponding probe reagent specific for a target analyte, wherein each of the nucleic acid labels comprised at least one pre-determined subsequence, e.g., a first (e.g., A1, A2, and A3) and a second (B1, B2, and B3) pre-determined subsequence, was prepared. The nucleic acid labels can comprise a nucleic acid sequence of any length. In some embodiments, the nucleic acid labels can comprise at least 15 nucleotides, at least 20 nucleotides, at least 22 nucleotides, or at least 24 nucleotides. A sample containing multiple target analytes was contacted with the target analyte-specific Dynabeads, so that the Dynabeads would bind to the respective target analyte on the sample. Any unbound Dynabeads was then removed, e.g., by washing. In the first readout, a set of three decoder probes, each with a distinct sequence complementary to the first pre-determined subsequences (e.g., A1*, A2*, and A3*) and a corresponding optical label (e.g., selected from red, green or blank), was added to the sample with bound Dynabeads, and then imaged with fluorescent microscopy ( FIG.  6 A ). The fluorescent signal was then removed, e.g., by photobleaching, from the previous stage before the next readout. In the second readout, a different set of three decoder probes, each with a distinct complementary sequence to the second pre-determined subsequences (e.g., B1*, B2*, B3*) and a corresponding optical label (e.g., selected from red, green blank), was added to the photobleached sample, and then imaged with fluorescent microscopy ( FIG.  6 B ). The temporal sequence of the optical signatures obtained from each bead can then be analyzed to determine the identity of the probe and thus the presence of the corresponding target analyte on the sample. Based on the intensity and/or coverage of the optical signals, the amount of the target analyte can also be determined. 
     By way of example only, a biotinylated anti- C. albicans  antibody (e.g., an commercially-available antibody from Pierce Antibodies PA1-27145) was conjugated with a plurality of different biotinylated nucleic acid labels (e.g., 8 different biotinylated SeqTag label sequences) using any conjugation methods known in the art. In one embodiment, the biotinylated anti- C. albicans  antibody was conjugated with a plurality of different biotinylated nucleic acid labels (e.g., biotinylated SeqTag label sequences) using a streptavidin-like protein (e.g., Neutravidin) as a bridge. The SeqTag label sequences are shown in Table 5. The SeqTag label sequences can comprise at least about 24 nucleotides. In some embodiments, the SeqTag label sequences can comprise DNA, RNA or a combination thereof. Each conjugate was incubated with a sample comprising  C. albicans , washed, and readout using any readout method as described herein, e.g., the displacement-hybridization method. 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 DNA sequences of exemplary SeqTag labels 
               
            
           
           
               
               
               
            
               
                 SEQ ID 
                 SeqTag 
                   
               
               
                 NO: 
                 label 
                 DNA Sequence 
               
               
                   
               
               
                 59 
                 SeqTag 1 
                 5′-Biotin - TTTCGCTTT 
               
               
                   
                   
                 CTGTAATGGAGTGGA - 3′ 
               
               
                   
               
               
                 60 
                 SeqTag 2 
                 5′-Biotin - TTTCGCTTT 
               
               
                   
                   
                 AGCCTAAGTGAAATC - 3′ 
               
               
                   
               
               
                 61 
                 SeqTag 3 
                 5′-Biotin - TTTCGCTTT 
               
               
                   
                   
                 TTTGGGGAAAAGACA - 3′ 
               
               
                   
               
               
                 62 
                 SeqTag 4 
                 5′-Biotin - TTTCGCTTT 
               
               
                   
                   
                 TAGGCATTAGCATTG - 3′ 
               
               
                   
               
               
                 63 
                 SeqTag 5 
                 5′-Biotin - TTTCGCTTT 
               
               
                   
                   
                 GGAAGCACCTATTCC - 3′ 
               
               
                   
               
               
                 64 
                 SeqTag 6 
                 5′-Biotin - TTTCGCTTT 
               
               
                   
                   
                 CTGGAGAAAGGGCCA - 3′ 
               
               
                   
               
               
                 65 
                 SeqTag 7 
                 5′-Biotin - TTTCGCTTT 
               
               
                   
                   
                 CGGTTCCAAAGACAC - 3′ 
               
               
                   
               
               
                 66 
                 SeqTag 8 
                 5′-Biotin - TTTCGCTTT 
               
               
                   
                   
                 GAAGCCGGTTATAGC - 3′ 
               
               
                   
               
            
           
         
       
     
     During the displacement hybridization method, by way of example only, as shown in  FIG.  7   , the yeast was incubated in readout step 1 with a mixture of all three “set 1” decoder probes, followed by an incubation with a mixture of the “set 2” decoder probes and the “set 1 displacers” (which are nucleic acid sequences to remove “set 1” fluorescence), and similarly with appropriate sets of decoder probes and displacers for steps 3 and 4. The decoder probes can comprise a nucleic acid sequence (e.g., DNA, RNA or a combination thereof) and a detection label, e.g., at its 5′ end. The nucleic acid sequence of the decoder probes can be of any length. In some embodiments, the decoder probes can comprise at least about 10 nucleotides, at least about 12 nucleotides, at least about 14 nucleotides, at least about 16 nucleotides, at least about 18 nucleotides, at least about 20 nucleotides or longer. Detection labels can be any art-recognized label described herein, e.g., fluorescent detection labels such as FAM, Cy3, and C 5 , or any labels described herein. Probe displacers, as described earlier, are nucleic acid sequences that are used to remove or displace the previous decoder probes hybridized to the nucleic acid labels (e.g., SeqTag labels) such that a different set of decoder probes can be added and hybridized to the nucleic acid labels. The probe displacers can have a nucleic acid sequence of any length. In some embodiments, the nucleic acid sequence of the probe displacers can be longer than that of the decoder probes. In some embodiments, the probe displacers can comprise at least about 12 nucleotides, at least about 14 nucleotides, at least about 16 nucleotides, at least about 18 nucleotides, at least about 20 nucleotides, at least about 21 nucleotides or longer. Tables 2 and 3 show DNA sequences of exemplary decoder probes (or readout probes) and probe displacers, respectively. As seen in  FIG.  7   , each biotinylated anti- C albicans  antibody conjugated with a different SeqTag label sequence properly stained the yeast and fluorescenced only as designated by its SeqTag label with appropriate sets of decoder probes and probe displacer in each readout step. 
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 DNA sequences of exemplary decoder probes 
               
            
           
           
               
               
               
            
               
                 SEQ ID 
                 Readout 
                   
               
               
                 NO: 
                 probe 
                 DNA Sequence 
               
               
                   
               
               
                 67 
                 Set 1 FAM 
                 5′-FAM - TTTTCCACTCCATTACAG - 3′ 
               
               
                   
               
               
                 68 
                 Set 1 Cy3 
                 5′-Cy3 - TTTGATTTCACTTAGGCT - 3′ 
               
               
                   
               
               
                 69 
                 Set 1 Cy5 
                 5′-Cy5 - TTTTGTCTTTTCCCCAAA - 3′ 
               
               
                   
               
               
                 70 
                 Set 2 FAM 
                 5′-FAM - TTTCAATGCTAATGCCTA - 3′ 
               
               
                   
               
               
                 71 
                 Set 2 Cy3 
                 5′-Cy3 - TTTGGAATAGGTGCTTCC - 3′ 
               
               
                   
               
               
                 72 
                 Set 2 Cy5 
                 5′-Cy5 - TTTTGGCCCTTTCTCCAG - 3′ 
               
               
                   
               
               
                 73 
                 Set 3 FAM 
                 5′-FAM - TTTGTGTCTTTGGAACCG - 3′ 
               
               
                   
               
               
                 74 
                 Set 3 Cy3 
                 5′-Cy3 - TTTGCTATAACCGGCTTC - 3′ 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 7 
               
             
            
               
                   
               
               
                 DNA sequences of exemplary probe displacers 
               
            
           
           
               
               
               
            
               
                 SEQ ID 
                 Probe 
                   
               
               
                 NO: 
                 Displacer 
                 DNA Sequence 
               
               
                   
               
               
                 75 
                 Set 1 
                 5′ - TCCACTCCATT 
               
               
                   
                 FAM-Displacer 
                 ACAGAAAGCG - 3′ 
               
               
                   
               
               
                 76 
                 Set 1 
                 5′ - GATTTCACTTA 
               
               
                   
                 Cy3-Displacer 
                 GGCTAAAGCG - 3′ 
               
               
                   
               
               
                 77 
                 Set 1 
                 5′ - TGTCTTTTCCC 
               
               
                   
                 Cy5-Displacer 
                 CAAAAAAGCG - 3′ 
               
               
                   
               
               
                 78 
                 Set 2 
                 5′ - CAATGCTAATG 
               
               
                   
                 FAM-Displacer 
                 CCTAAAAGCG - 3′ 
               
               
                   
               
               
                 79 
                 Set 2 
                 5′ - GGAATAGGTGC 
               
               
                   
                 Cy3-Displacer 
                 TTCCAAAGCG - 3′ 
               
               
                   
               
               
                 80 
                 Set 2 
                 5′ - TGGCCCTTTCT 
               
               
                   
                 Cy5-Displacer 
                 CCAGAAAGCG - 3′ 
               
               
                   
               
               
                 81 
                 Set 3 
                 5′ - TGTGTCTTTGG 
               
               
                   
                 FAM-Displacer 
                 AACCGAAAGCG - 3′ 
               
               
                   
               
               
                 82 
                 Set 3 
                 5′ - GCTATAACCGG 
               
               
                   
                 Cy3-Displacer 
                 CTTCAAAGCG - 3′ 
               
               
                   
               
            
           
         
       
     
     Content of all patents and other publications identified herein is expressly incorporated herein by reference for all purposes. These publications are provided solely for their disclosure prior to the filing date of the present application. Nothing in this regard should be construed as an admission that the inventors are not entitled to antedate such disclosure by virtue of prior invention or for any other reason. All statements as to the date or representation as to the contents of these documents is based on the information available to the applicants and does not constitute any admission as to the correctness of the dates or contents of these documents.