Patent Publication Number: US-2010112719-A1

Title: Electronic signal amplification in field effect device based chemical sensors

Description:
BACKGROUND 
     Technical Field 
     The disclosure relates to chemical sensors, more particularly the disclosure relates to solid state sensors capable of chemical sensing by detection of electrostatic changes associated with a recognition event. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a particular embodiment of an analyte coupled to an enhanced charge marker. 
         FIG. 2  is a diagram illustrating a particular embodiment of a secondary probe coupled to an enhanced charge marker. 
         FIG. 3  is a diagram illustrating a particular embodiment of a chemical sensor capable of detecting an analyte coupled to an enhanced charge marker. 
         FIG. 4  is a diagram illustrating a particular embodiment of a chemical sensor capable of detecting an analyte via a secondary probe coupled to an enhanced charge marker. 
         FIG. 5  is a diagram illustrating a particular embodiment of a system comprising a sensor to detect an analyte. 
         FIG. 6  is a block diagram illustrating a particular embodiment of a process for detecting the presence of an analyte in a sample. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of claimed subject matter related to chemical sensors comprising field effect devices capable of detection of electrostatic changes associated with chemical recognition events. However, it will be understood by those skilled in the art that claimed subject matter may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure claimed subject matter. 
     Throughout the following disclosure the term ‘chemical sensor’ is used and is intended to refer to a device capable of detection of an analyte that combines a detecting component or ‘probe’ with an electronic and/or mechanical detector element. The terms ‘biomolecule’ and ‘biomolecular’ are used throughout the following disclosure and are intended to refer to one or more molecules that may be biologically active and may be naturally occurring in living organisms or may be synthesized by a variety of non-naturally occurring methods. The term ‘analyte’ is used throughout the following disclosure and is intended to refer to any chemical, biochemical and/or biomolecular substance that is undergoing analysis. 
     The term ‘molecular recognition event’ or ‘recognition event’ is used throughout the following disclosure and is intended to refer to an interaction between a probe or capture molecule and an analyte giving rise to a specific and/or selective recognition of an analyte. Molecular recognition or specific recognition refers to the specific interaction between two or more molecules typically through non-covalent bonding interactions such as hydrogen bonding, metal coordination, hydrophobic forces, van der Waals forces, π-π interactions, and or electrostatic effects. Two molecules that are able to undergo a molecular recognition event are referred to as having molecular complementarity. Molecular complementarity is sometimes thought of as being similar to the way a key fits into a lock in that a key has a specific shape that is designed for and capable of interacting with a specific lock. Examples of molecular recognition events include receptor-ligand, antigen-antibody and sugar-lectin. 
     The terms target, target molecule, or analyte refer to a molecule of interest that is to be detected. The terms probe, probe molecule, or capture molecule refer to a molecule that selectively recognizes or binds to a target molecule or undergoes a chemical reaction with a target molecule. The probe or probe molecule generally, but not necessarily, has a known molecular structure or sequence. Probe molecules are molecules capable of undergoing binding or molecular recognition events with target molecules. Probes may be naturally-occurring or synthetic molecules. Probes can be employed in their unaltered state or as aggregates with other species. Examples of probes which can be used in conjunction with the disclosed method and device include, but are not limited to, antibodies, peptides, proteins, enzymes, receptors, targets, pharmaceutical drugs, cofactors, lectins, sugars, polysaccharides, cells, cellular membranes, and organelles. The probe molecule or the target molecule can be a ligand or a receptor. A ligand is a molecule that typically binds to another molecule, usually referred to as a receptor, the level of specificity can vary. Usually, the term ligand is given to the smaller of the two molecules in the ligand-receptor pair, but it is not necessary for this to be the case. A receptor can be considered to be a molecule that has an affinity for a particular ligand. Typically, in a cell, a receptor is a protein molecule to which a mobile signaling molecule can specifically bind. Cellular receptors include opiate receptors, neurotransmitter receptors, steroid receptors, intracrine peptide hormone receptors, and hormone receptors. Examples of ligands include, but are not limited to, agonists and antagonists for cell membrane receptors, toxins and venoms, viral epitopes, hormones, hormone receptors, peptides (such as neurotransmitters), cofactors, pharmaceutical drugs, lectins, sugars, and oligosaccharides. 
     Throughout the following disclosure particular embodiments of solid-state chemical sensors are disclosed. Biomolecular sensors for detecting analytes comprising various chemical and biomolecular compounds are discussed. Particular embodiments of the device and method disclosed herein may be useful for detecting many varieties of organic and inorganic chemicals, biochemicals and/or biomolecules using a variety organic and inorganic chemicals and compounds such as probes or capture molecules and claimed subject matter is not limited in this regard. Such analytes and probes may be naturally occurring and/or synthetic, organic and/or inorganic chemicals, biochemicals and/or biomolecules and claimed subject matter is not limited in this regard. 
       FIG. 1  illustrates a particular embodiment of an analyte  102  coupled to enhanced charge marker (ECM)  108 . In a particular embodiment, ECM  108  is a molecule carrying a net positive and/or negative charge. ECM  108  may be an electrostatic marker configured to be coupled to an analyte  102 . In another embodiment, ECM  108  may be coupled to a probe (see  FIG. 2 ) and claimed subject matter is not limited in this regard. 
     In a particular embodiment, ECM  108  may be used to mark a probe and/or analyte for chemical assay using a chemical sensor wherein detection of an analyte depends on detecting a physical change associated with a recognition event. During such a chemical assay, ECM  108  is operable to amplify steric, electrostatic and/or mechanical changes during the recognition event between the probe and analyte thus increasing the sensitivity and/or selectivity of the assay. 
     A chemical sensor may detect analyte  102  by detecting various physical changes associated with molecular recognition events between a probe and analyte. According to a particular embodiment, ECM  108  may be engineered or synthesized to carry a net charge sufficient to enhance the physical changes associated with molecular recognition events during detection. Such physical changes or effects may include steric, electrostatic, conformational, charge and/or conductivity affects. In an embodiment, ECM  108  comprises a net charge greater than 2 or less than −2. 
     In a particular embodiment an ECM  108  may be selected based at least in part on net charge of a target analyte and/or probe to which the ECM is to be coupled. ECM  108  may be a substance different from the target analyte and/or probe. In the following examples the target analyte and/or probe may be any of a variety of species that have a net charge in the specified range and claimed subject matter is not limited in this regard. 
     For example, in a particular embodiment in a working solution having a pH in the range of 3-10 where the analyte or probe has a net charge in the range of about −20 to 20, an ECM  108  comprising an effective charge in the range of about −10 to −2 or about 2 to 10 may be selected to be coupled to the analyte and/or probe. Effective charge may be a net charge of ECM  108  after subtracting the net charge of the analyte or probe. In this embodiment, ECM  108  may improve the sensitivity of a chemical sensor by enhancing physical changes associated with molecular recognition events during detection of an analyte as described above. ECM  108  may comprise, for example, a polypeptide or other polymer comprising about 20 mers in one embodiment, but claimed subject matter is not limited in this regard. 
     In another particular embodiment in a working solution having a pH in the range of 3-10 where the analyte or probe has a net charge in the range of about −40 to 40, an ECM  108  comprising an effective charge in the range of about −15 to −2 or about 2 to 15 may be selected to be coupled to the analyte and/or probe. In this embodiment, ECM  108  may improve the sensitivity of a chemical sensor by enhancing physical changes associated with molecular recognition events during detection of an analyte as described above. ECM  108  may comprise, for example, a polypeptide or other polymer comprising about 30 mers in one embodiment, but claimed subject matter is not limited in this regard. 
     In another particular embodiment in a working solution having a pH in the range of 6-8 where the analyte or probe has a net charge in the range of about −3 to 3 (such as a protein), an ECM  108  comprising an effective charge in the range of −15 to −2 or about 2 to 15 may be selected to be coupled to the analyte and/or probe. In this embodiment, ECM  108  may improve the sensitivity of a chemical sensor by enhancing physical changes associated with molecular recognition events during detection of an analyte as described above. ECM  108  may comprise, for example, single-stranded DNA (ssDNA) or other polymer comprising about 15 mers in one embodiment, but claimed subject matter is not limited in this regard. 
     In another particular embodiment in a working solution having a pH in the range of 6-8 where the analyte or probe has a net charge in the range of about −10 to 10 (such as various metabolites), an ECM  108  comprising an effective charge in the range of about −25 to −2 or about 2 to 25 may be selected to be coupled to the analyte and/or probe. In this embodiment, ECM  108  may improve the sensitivity of a chemical sensor by enhancing physical changes associated with molecular recognition events during detection of an analyte as described above. ECM  108  may comprise, for example, ssDNA or other polymer comprising about 25 mers in one embodiment, but claimed subject matter is not limited in this regard. 
     ECM  108  may comprise phosphate, carboxylate, amine and/or sulfonate groups and claimed subject matter is not limited in this regard. In a particular embodiment, phosphate, carboxylate, and/or sulfonate groups may be negatively charged under biological conditions (ph 6.0-8.0) whereas amine groups may comprise positive charges under biological conditions. 
     In another particular embodiment, ECM  108  may comprise an artificial and/or native polymer backbone with functional groups. Such polymer backbone may comprise a variety of species including; negative DNA (deoxyribonucleic acid) oligomers, negative or positive peptide oligomers and/or synthetic polymers with positive or negative side groups. In a particular embodiment, such side groups may comprise sulfonate and/or carboxylated aliphatic and aromatic amines and/or heterocyclic-organometalic complexes. Additionally, in a particular embodiment, a ECM  108  may be chosen to comprise a higher or lower pH than the pH of sample medium  122  (working solution). 
     In another embodiment, ECM  108  may comprise a number of charged groups where the number of charged groups on ECM  108  is selected to be inversely proportional to the concentration of analyte  102  in sample medium  122 . For example, if analyte  102  concentration is low in sample medium  122 , an ECM  108  may be selected comprising a greater number of charged groups to enhance sensitivity of a chemical sensor. In another example, if analyte concentration is high, ECM  108  may be selected comprising a lower number of charge groups to minimize unintended interactions between charged groups. 
     According to a particular embodiment, ECM  108  may be coupled to analyte  102  by a variety of methods such as, for instance, carbodiimide coupling of sDNA, peptide nucleic acid (PNA), and/or a peptide unit to analyte  102  and/or secondary probe  150 . In another particular embodiment, short peptide or PNA sequences may be coupled to ECM  108  comprising other charged species as described above. Such short peptide or PNA sequences may be engineered such that they may bind to the analyte by specific interaction on specific locations. However, these are merely examples of a variety of enhanced charge markers and claimed subject matter is not limited in this regard. 
     According to a particular embodiment, marking analyte  102  with ECM  108  may enable enhanced detection of analyte  102  by chemical sensors capable of recognizing analyte  102  wherein the chemical sensor detects the presence of analyte  102  by sensing steric and/or electrostatic changes brought about during a recognition event. Such sensors may comprise a variety of devices and/or materials capable of detecting steric, electrostatic, conformational, charge and/or conductivity changes by enhancing an electrostatic charge at an interface upon analyte  102  interaction with probe  150 . Such physical changes may activate a transducing mechanism of a sensor. Such chemical sensors may be field effect transistors, piezo-electric materials, crystal material, ion-sensitive field effect transistors (ISFET), electrolyte-insulator-semiconductor (EIS), amperometric or potentiometer electrode sensor, capacitance sensor and/or reflectance and refractive sensors (for example, surface plasmon resonance (SPR), Elipsometery, etc) and claimed subject matter is not limited in this regard. 
       FIG. 2  illustrates a particular embodiment of secondary probe  150  coupled to charged ECM  108 . In a particular embodiment, secondary probe  150  coupled to ECM  108  may enable enhanced detection of an analyte (not shown). In a particular embodiment, ECM  108  may be a substance different from secondary probe  150 . In a particular embodiment, an enhanced charge of ECM  108  may enable an increased sensitivity in chemical sensors capable of detecting the presence of an analyte by detecting physical changes such as steric, electrostatic, conformational, charge and/or conductivity affects associated with a recognition event between an analyte immobilized on one or more probes of the chemical sensor and secondary probe  150 . According to a particular embodiment, such a chemical sensor may be capable of enhance detection because steric, electrostatic, conformational, charge and/or conductivity affects corresponding to a recognition event between secondary probe  150  and an immobilized analyte may be exaggerated by the presence of an enhanced charge on ECM  108 . 
       FIG. 3  illustrates an embodiment of sensor  100  during detection of analyte  102  marked with a poly-charged ECM  108 . Block  180  on the left depicts sensor  100  before exposure to a sample  122  containing analyte  102 . Block  182  on the right depicts sensor  100  after exposure to sample  122  where probes  104  and analyte  102  have undergone a recognition event and analyte  102  is coupled to probes  104 . 
     In a particular embodiment, sensor  100  may be a chemical sensor capable of detecting a variety of chemical, biochemical and biomolecular species and claimed subject matter is not limited in this regard. In a particular embodiment, sensor  100  may comprise one or more embedded field effect devices (FED)  103  disposed in substrate  106 . Sensor  100  may comprise a single FED  103  or may comprise an array of FEDs  103  (as shown in  FIG. 3 ). Such FEDs  103  may comprise field effect transistors, piezo-electric materials, crystal material, ion-sensitive field effect transistors (ISFET), and/or electrolyte-insulator-semiconductor (EIS) devices and claimed subject matter is not limited in this regard. FED  103  may be sterically and/or electrostatically sensitive and may be coupled to a capture molecule such as a probe  104 . Sensor  100  may be fabricated in a variety of dimensions, such as, microscale or nanoscale fabrication and claimed subject matter is not limited in this regard. 
     In a particular embodiment, probe  104  may be directly in contact with the ambient, such as, sample  122 . In a particular embodiment, probe  104  may be coupled to member  110  extending from substrate  106 . Sensor  100  may be exposed to sample  122  containing analyte  102 . Such a sample may be in solid, liquid and/or gas phase and may comprise a variety of species from which an analyte  102  may be differentiated. Sensitivity and specificity of sensor  100  may depend on a number of variables such as, for instance, the type of sterically and/or electrostatically sensitive device or material used and the specificity of probe  104  and claimed subject matter is not limited in this regard. In a particular embodiment, ECM  108  may enable enhanced detection of an analyte  102  with respect to the results that may be achieved without coupling analyte  102  to ECM  108 . 
     In a particular embodiment, during a recognition event, probe  104  may be coupled to an outside surface of member  110  and may be capable of forming a bond to analyte  102  and thereby inducing electrostatic effects and mechanical stress on member  110  due to steric and/or electrochemical effects of bonding. In another particular embodiment, charge density rearrangement of analyte  102  may occur during such a recognition event. Such charge density rearrangement may change the net charge of analyte  102  and enable a surface potential on member  110 . Such a change in the surface potential in member  110  may modulate channel conductivity in FED  103  by changing a voltage on a gate (not shown) of FED  103 . In another particular embodiment, member  110  may be coupled to a variety of probes that may be capable of bonding to different analytes. Thus, sensor  100  as disclosed herein may be capable of detecting and/or recognizing one or more analytes to enable detection of different analytes in the same sample. However, these are merely examples of probe configurations for a biosensor and claimed subject matter is not so limited. 
     In a particular embodiment, probe  104  may be immobilized on one or more members  110  extending from substrate  106 . Such members  110  may comprise a variety of structures such as cantilevers, blades, cylinders, flexible gate electrodes (FGE) and/or nanotubes and claimed subject matter is not limited in this regard. According to a particular embodiment, member  110  may be coupled to FED  103  and may be operable to translate steric, electrostatic, conformational, charge and/or conductivity changes related to a recognition event into a signal in FED  103 . According to a particular embodiment, member  110  may comprise an FGE where such an electrode may comprise a selectively permeable or reactive coating, such as, for instance, a lipid bilayer, hydrogel, polyvinyl acetate (PVA) and polyethylene glycol (PEG) based functional polymers and/or polyelectrolyte and claimed subject matter is not limited in this regard. According to a particular embodiment, an inside surface  130  of sensor  100  may be coated with various selectively permeable and/or reactive coatings and claimed subject matter is not limited in this regard. 
     In a particular embodiment, probe  104  may comprise a variety of materials and/or compounds that if exposed to sample  122  may be capable of recognizing and/or detecting the presence of analyte  102  in sample  122  to a greater extent than other substances that may be found in sample  122 . Such recognition and/or detection may comprise probe  104  bonding, binding and/or coupling to analyte  102  via covalent and/or non-covalent or other forces. In a particular embodiment, recognition and/or detection may comprise probe  104  exhibiting steric and/or electrostatic behavioral changes associated with the presence of analyte  102  in a sample. Such a recognition event may trigger conformational and/or electrostatic changes in probe  104  that may be translated to FED  103  and/or a FED  103  array. In a particular embodiment, detection may be measured by a signal induced by FED  103  in response to recognition of analyte  102 . 
     In a particular embodiment, probe  104  may comprise a variety of biomolecular species, such as: antibodies, antibody fragments, single-chain antibodies, genetically engineered antibodies, artificial antibodies (for example, affibodies or phages caring binding peptides), peptide nucleic acids, proteins, peptides, binding proteins, receptor proteins, transport proteins, lectins, substrates, inhibitors, activators, ligands, hormones, neurotranamitters, growth factors, cytokines, carbohydrates, aptamers, lipids, lipid bilayers and/or charged polymers and claimed subject matter is not limited in this regard. 
     In one example embodiment, an ECM  108  comprises a sodium poly(aspartate) molecule. An ECM  108  comprising a sodium poly(aspartate) molecule may be formed, for example, by reacting a molecule comprising a backbone having repeating succinimide units with sodium hydroxide to form a carboxylated functional group on every monomer unit. ECM  108  comprising poly(aspartate) may be a linear molecule having the formula —[CH(CH 2 CO 2 Na)CONH] n — where n comprises a value from about 20 to about 50, or about 50 to about 500, or about 500 to about 5000, or combinations thereof. In another embodiment, n comprises a value from about 10 to about 100. Other useful substituents may include amine and/or sulfonate groups. For example, ECM  108  may comprise polystyrene sulfonic acid, poly(2-acrylamido-2-methyl-1-propanesulfonic acid), poly(allylamine hydrochloride), or poly(acrylamido-N-propyltrimethylammonium chloride), however, claimed subject matter is not so limited. 
     An ECM  108  such as a sodium poly(aspartate) molecule may be attached to a probe  104  such as, for example, immunoglobulin G (IgG) comprising anti-PSA antibody (Prostate Specific Antigen). Such ECM  108  may be coupled with the antibody using, for example, a carbodiimide coupling reagent such as 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) to form an amide bond between the ECM  108  and the probe  104 . A resulting theoretical net charge on such ECM-antibody complex may comprise one negative charge per unit monomer at pH higher than pKa values of about 4.5. Part of such theoretical net charge may be screened to an extent by counter ions and polarity of water molecules, for example, however, significant charge may remain unscreened to affect the device  103 . Subject matter is not necessarily limited in this regard. 
     In a particular embodiment, analytes  102  may comprise a variety of biomolecular species, such as: amino acid, peptide, polypeptide, protein, glycoprotein, lipoprotein, antibody, sugar, carbohydrate, oligosaccharide, polysaccharide, fatty acid, lipid, hormone, metabolite, growth factor, cytokine, chemokine, receptor, neurotransmitter, antigen, allergen, antibody, substrate, metabolite, cofactor, inhibitor, drug, pharmaceutical, nutrient, biohazardous agent, infectious agent, prion, vitamin, heterocyclic aromatic compound, carcinogen, mutagen, waste product, virus, bacterium,  Salmonella, Streptococcus, Legionella, E. coli, Giardia, Cryptosporidium, Rickettsia,  spore, mold, yeast, algae, amoebae, dinoflagellate, unicellular organism, pathogen, prion and/or a cell and claimed subject matter is not limited in this regard. 
     In a particular embodiment, substrate  106  may be comprised of a variety of materials, such as, for instance: silicon, silicon-oxide, gallium arsenide, silicon germanium, silicon carbide, gallium phosphide and/or polysilicon and claimed subject matter is not so limited. According to a particular embodiment, substrate  106  may be disposed on a support structure  124 . According to a particular embodiment, the assembly may be sealed with a coating  130  that may be substantially impermeable to a variety of substances in a variety of physical phases and claimed subject matter is not so limited. 
     According to a particular embodiment, coating  130  may comprise any of a variety of materials, such as, photo resists, polyimide, epoxy, metal nitride, metal oxide, or any other barrier materials know to those of skill in the art and claimed subject matter is not limited in this regard. Such coating  130  may enable sensor  100  to be immersed in a liquid or gas sample and to be used repeatedly while resisting wear and device failure. However, this is merely an example of a method of protecting a surface of substrate  106 /support  124  assembly and claimed subject matter is not so limited. 
     In a particular embodiment, sensor  100  may be exposed to sample  122  by a variety of methods, such as, for instance, by titrating an aqueous sample  122  containing analyte  102  directly onto FED  103  array and claimed subject matter is not limited in this regard. In a particular embodiment, sensor  100  may be partially enclosed in a package (see  FIG. 5 ). Such a package may be configured in a variety of ways to enclose all or a portion of sensor  100  and claimed subject matter is not limited in this regard. 
       FIG. 4  illustrates an embodiment of sensor  400  during detection of analyte  402 . In a particular embodiment, block  480  depicts sensor  400  prior to exposure to a sample  122  containing analyte  402 . Block  482  depicts sensor  400  after exposure to sample  422  where probes  404  and analyte  402  have undergone a recognition event and analyte  402  is coupled to one or more probes  404 . Block  484  depicts sensor  400  after sample  422  has been rinsed away and sensor  422  is exposed to a working solution comprising a secondary probe  412  coupled to an enhanced charge marker (ECM)  408 . In this particular embodiment of a chemical assay using a secondary probe  412  an analyte  402  may be detected by sensor  400  if a recognition event between a secondary probe  412  and an immobilized analyte  402  occurs. Such an assay may have an increased specificity and/or selectivity due to use of two probes capable of undergoing recognition events in the presence of analyte  402 . According to a particular embodiment, such an assay may also have an increased sensitivity due to an enhanced charge marker  408  marking the secondary probe  412 . As described above, such an enhanced charge may increase steric and electrostatic effects brought on by a recognition event between a secondary probe and an analyte. 
     In a particular embodiment, secondary probe  412  may comprise monoclonal antibodies such as monoclonal antibodies raised against Prostate Specific Antigen (anti-PSA). In a particular embodiment, anti-PSA may be used to detect analyte  402  where analyte  402  is PSA. Such a secondary probe  412  may be coupled to ECM  408  by a variety of methods. For instance, ECM  108  may comprise peptide nucleic acid (PNA). In a particular embodiment, a PNA ECM  108  may be coupled to secondary probe  412  by coupling carbodiimide to the PNA. According to a particular embodiment, ECM  108  may have a variety of lengths. In one embodiment, ECM  108  comprises between about 5 mers to about 50 mers. Other lengths may be used in other embodiments and claimed subject matter is not limited in this regard. However, this is merely an example of marking a secondary probe with a particular electrostatic marker and claimed subject matter is not so limited. 
       FIG. 5  illustrates a particular embodiment of a sensor  500  for detecting analyte  502  wherein analyte  502  is electrostatically labeled with ECM  508 . In a particular embodiment, ECM  508  may be a native or synthetic polymer comprising functional groups having a pKa lower (negative) or higher (positive) than the pH of a sample  522 . Sensor  500  may be immersed in sample  522  within package  523 . In a particular embodiment, sensor  500  may comprise FET  503  embedded in substrate  524 . An outside surface of the substrate  524 /FET  503  assembly may be sealed with impermeable coating  530 . However, this is merely an example of a method of protecting a surface of the substrate  524 /FET  503  assembly and claimed subject matter is not so limited. 
     In a particular embodiment, member  510  may be an extended gate electrode (FGE), may function as the FET  503  gate electrode and may be coupled to and extend from gate  516 . In a particular embodiment, member  510  may be directly in contact with the ambient, such as, sample  522 . Member  510  may have a substantially rectangular shape and may comprise or be coupled to an analyte sensitive material such as probe  504 . According to a particular embodiment, probes  504  may be located on a single side of member  510  to enable mechanical stress to flex member  510  along arc  520 . However, this is merely an example of a shape of a member  510  and a particular placement of probes  504  and claimed subject matter is not so limited. 
     Upon detection of analyte  502 , member  510  may exert both mechanical stress on FET  503  and induce an electrostatic charge in gate  516 . A specific recognition event between probes  504  and analyte  502  marked with ECM  508  may deflect FGE  510 , along an arc  520  and may induce strain on FET  503  which may transform into conductivity effects in channel  518  of FET  503 . 
     Sensor  500  may be immersed in sample  522  contained in package  523 . Package  523  may be configured in a variety of ways and claimed subject matter is not limited in this regard. In a particular embodiment, sensor  500  may communicate detection of analyte  502  to a processing unit  550 , such as a computer CPU and/or mobile unit processor and claimed subject matter is not limited in this regard. Communication may be via communication route  555  by any of a variety of communication techniques, such as for instance via wireline and/or wireless communication and claimed subject matter is not limited in this regard. 
     In another particular embodiment, sensor  500  may comprise a sensitive hydrogel (not shown). Such a hydrogel may be sensitive to a variety of stimuli and substances. Upon recognition of a substance or stimulus to which a hydrogel is sensitive, the volume of the hydrogel may change. According to a particular embodiment, member  510  may be in contact with a hydrogel and may undergo a change in volume upon sensing a probe  504  coupled to ECM  508 . Such ECM  508  may amplify a volume change due to enhanced steric and/or electrostatic effects of charged marker ECM  508  on a hydrogel. In a particular embodiment, a hydrogel may deflect member  510 , along an arc  520  and may induce strain on FET  503  which may transform into conductivity effects in channel  518 . In a particular embodiment, such a hydrogel may be immobilized on a surface of member  510  and/or member  510  may be immersed in a sensitive hydrogel within an enclosed package. According to a particular embodiment, a sensitive hydrogel may comprise one or more biomolecular probes sensitive to one or more analytes. However, these are merely examples of a sensor  500  comprising a hydrogel and claimed subject matter is not limited in this regard. 
       FIG. 6  is a block diagram illustrating a process  600  for detecting an analyte. At block  602 , a sensor may be prepared by immobilizing a probe or capture molecule on a sensor surface and/or members extending from a sensor surface. Such probes or capture molecules may be capable of undergoing a recognition event with an analyte. According to a particular embodiment, process  600  may proceed to block  604  where a sample matrix (containing the analyte) and/or secondary probe may be prepared by marking with an electrostatic marker as described above. Process  600  need not proceed according in the order provide in  FIG. 6 . In a particular embodiment, analytes and secondary probes may be prepared at any time and claimed subject matter is not limited in this regard. 
     Process  600  may proceed to block  606  where a sample containing one or more analytes of interest may be exposed to the sensor. In a particular embodiment, exposing a sample to the sensor may immobilize an analyte on a surface of the sensor. Process  600  may proceed to block  608  where if the analyte is marked with an ECM process  600  may proceed to block  610  and if the analyte is not marked then process  600  may proceed to block  612 . 
     At block  610  of process  600 , an analyte may be detected by a sensor upon occurrence of a specific recognition event. During such a recognition event electrostatic and/or steric changes associated with the recognition event may translate to detecting devices of the sensor. When an analyte is detected, such detection may be communicated to a computing unit. 
     At block  612  of process  600  an analyte may be exposed to a secondary probe marked with an electrostatic marker. Process  600  may proceed to block  610  where an analyte may be detected by a sensor upon occurrence of a specific recognition event between the secondary probe and the analyte. During such a recognition event, electrostatic and/or steric changes associated with the recognition event may translate to detecting devices of the sensor. When an analyte is detected, such detection may be communicated to a computing unit. 
     While certain features of claimed subject matter have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such embodiments and changes as fall within the spirit of claimed subject matter.