Patent Description:
<CIT> describes a method for covalently immobilizing probe-biomolecules on organic surfaces by means of photoreactive crosslinking agents. The method has in practice proven to be advantageous particularly because it permits an immobilization of probe biomolecules on unreactive surfaces, such as silanized glass supports and substrates made of standard commercial plastics. A polymer is used in the method described in <CIT> to form a type of three-dimensional network onto which the probe biomolecules can be bonded, either at the network's surface or in the inside of the network. Compared to an organic surface on which the probe biomolecules are only immobilized in two-dimensional form, the three-dimensional immobilization of the biomolecules in the polymer and/or copolymer network permits a higher density of the probe biomolecules on the organic surface. This increases the amount of analyte which can be bonded per surface unit of the organic surface. Use of the surface as biological sensor thus gives rise to a higher measurement accuracy and a high measurement dynamic.

However, a disadvantage of the methods and polymer networks described in <CIT> is that analyte molecules or analyte components which bind to probe biomolecules arranged on or close to the surface of the polymer network can block the network. Further analyte molecules or analyte constituents can then no longer bind as well to as yet unbound probe biomolecules which are arranged at a greater distance from the surface of the network in its interior.

Thus, there is a need for improved polymer networks.

<CIT> relates to microarrays having a substrate and a plurality of three-dimensional microstructures formed on the substrate, where each of the three-dimensional microstructures is made with polymer material and has a plurality of reactive sites formed on its surface and interior pores. The polymer material is polymer gel or other porous polymer.

<NPL> relates to a process for immobilizing biomolecules on polymer substrates, where in the process probe molecules are mixed with a photoactive copolymer in aqueous buffer, spotted onto a solid support, and cross-linked as well as bound to the substrate during brief flood exposure to UV light.

<NPL>) relates to superporous poly(<NUM>-hydroxyethyl methacrylate) (PHEMA) scaffolds as supports for cell cultivation, where superpores were formed by salt-leaching.

The disclosure provides three-dimensional polymer networks comprising a crosslinked polymer and a plurality of channels that extend from a surface and/or near a surface of the network into the network's interior. The networks are suitably covalently attached to a surface. A majority of probes, such as a biomolecule, are immobilized on the surface of the network and throughout the interior of the network, providing a sensor for detecting the presence of and/or measuring the amount of an analyte in a sample. For example, nucleic acid probes can be used to detect complementary nucleic acids present in a sample and antibody probes can be used to detect antigens present in a sample. The networks of the invention allow for faster hybridization of a given amount of analyte than networks lacking channels because the channels can effectively increase the surface area of the network, exposing more probes to the sample in a given amount of time. Additionally, the networks of the invention can bind more analyte than the same volume of a channel-free network because the channels decrease or eliminate the problem whereby analyte or other components of a sample bound to probes at or near the surface of the network block access to probes located in the interior of the network. Another advantage of the networks of the invention is that the high amount of analyte loading made possible by the channels allows for a more sensitive detection of analyte than may be possible with a channel-free network, i.e., the signal to noise ratio can be improved compared to channel-free networks because a given amount of analyte can be concentrated in a smaller network volume. Yet another advantage of the networks of the invention is that the high analyte loading made possible by the channels allows for quantification of a wider range of analyte concentrations compared to channel-free networks.

This disclosure also provides arrays comprising a plurality of the three-dimensional networks according to claims <NUM> to <NUM> and a substrate. Arrays of the disclosure can be used to detect and/or measure one or more analytes in one or more samples simultaneously. The arrays of the disclosure can be washed and reused, providing a significant cost advantage over single use arrays. Another advantage of the arrays of the disclosure is that they can be manufactured in a simple manner because all of the components needed to make an individual network can be applied as a single mixture onto a surface of the substrate during the manufacturing process.

This disclosure also provide processes for making the three-dimensional networks according to anyone of the claims <NUM> to <NUM> and arrays according to anyone of claims <NUM> to <NUM>. The three-dimensional networks of the disclosure can be made by crosslinking a polymer in the presence of salt crystals, preferably needle-shaped salt crystals, and subsequently dissolving the salt crystals to leave behind channels in the crosslinked polymer network.

This disclosure also provides processes for using the three-dimensional networks according to anyone of the claims <NUM> to <NUM> and arrays according to anyone of claims <NUM> to <NUM> to detect and/or measure an analyte in a sample, preferably a liquid sample.

The three-dimensional networks of the invention comprise a crosslinked polymer, e.g., a polymer according to <NPL> or <CIT>. The three-dimensional networks of the invention further comprise a plurality of channels and further comprise one or more probes immobilized on the network.

Polymers that can be used to make the networks are described in Section <NUM>. Cross-linkers than can be used to make the networks are described in Section <NUM>. Features of the one or more channels are described in Section <NUM>. Probes that can be immobilized on the networks are described in Section <NUM>.

The three-dimensional networks of the invention comprise a crosslinked homopolymer, copolymer, mixtures of homopolymers, mixtures of copolymers, or mixtures of one or more homopolymers and one or more copolymers. The term "polymer" as used herein includes both homopolymers and/or copolymers. The term "copolymer" as used herein includes polymers polymerized from two or more types of monomers (e.g., bipolymers, terpolymers, quaterpolymers, etc.). Copolymers include alternating copolymers, periodic copolymers, statistical copolymers, random copolymers, block copolymers, linear copolymers and branched copolymers. The three-dimensional networks of the disclosure can comprise any combination of the foregoing types of polymers. Reagents and methods for making such polymers are known in the art (see, e.g., <NPL>; <NPL>; <NPL>; <NPL>).

Preferred polymers are hydrophilic and/or contain hydrophilic groups. The polymer is water soluble. In an embodiment, the polymer is a copolymer that has been polymerized from two or more species of monomers selected to provide a desired level of water solubility. For example, water solubility of a copolymer can be controlled by varying the amount of a charged monomer, e.g., sodium <NUM>-vinylsulfonate, used to make the copolymer.

When crosslinked, water soluble polymers form water-swellable gels or hydrogels. Hydrogels absorb aqueous solutions through hydrogen bonding with water molecules. The total absorbency and swelling capacity of a hydrogel can be controlled by the type and degree of cross-linkers used to make the gel. Low crosslink density polymers generally have a higher absorbent capacity and swell to a larger degree than high crosslink density polymers, but the gel strength of high crosslink density polymers is firmer and can maintain network shape even under modest pressure.

A hydrogel's ability to absorb water is a factor of the ionic concentration of the aqueous solution. In certain embodiments, a hydrogel of the disclosure can absorb up to <NUM> times its weight (from <NUM> to <NUM> times its own volume) in deionized, distilled water and up to <NUM> times its weight (from <NUM> to <NUM> times its own volume) in saline. The reduced absorbency in saline is due to the presence of valence cations, which impede the polymer's ability to bond with the water molecule.

The three-dimensional network of the disclosure can comprise a copolymer that has been polymerized from one, two, thee, or more than three species of monomers, wherein one, two, three or more than three of the species of monomers have a polymerizable group independently selected from an acrylate group (e.g., acrylate, methacrylate, methyl methacrylate, hydroxyethyl methacrylate, ethyl acrylate, <NUM>-phenyl acrylate), an acrylamide group (e.g., acrylamide, methacrylamide, dimethylacrylamide, ethylacrylamide), an itaconate group (e.g., itaconate, <NUM>-methyl itaconate, dimethyl itaconate) and a styrene group (e.g. styrene, <NUM>-methyl styrene, <NUM>-ethoxystyrene). Preferred polymerizable groups are acrylate, methacrylate, ethacrylate, <NUM>-phenyl acrylate, acrylamide, methacrylamide, itaconate, and styrene. In some embodiments, one of the monomers used to make the copolymer is charged, e.g., sodium <NUM>-vinylbenzenesulfonate.

The polymer used to make a network of the invention can comprise at least one, at least two, or more than two cross-linker groups per molecule. A cross-linker group is a group that covalently bonds the polymer molecules of the network to each other and, optionally, to probes and/or a substrate. Copolymers that have been polymerized from two or more monomers (e.g., monomers having a polymerizable group independently selected from those described in the preceding paragraph), at least one of which comprises a cross-linker, are suitable for making a three-dimensional network of the disclosure. Exemplary cross-linkers are described in Section <NUM>. A preferred monomer comprising a cross-linker is methacryloyloxybenzophenone (MABP) (see <FIG>).

In a preferred embodiment, the copolymer is a bipolymer or a terpolymer comprising a cross-linker. In a particularly preferred embodiment, the copolymer comprises p(Dimethylacrylamide co methacryloyloxybenzophenone co Sodium <NUM>-vinylbenzenesulfonate) (see <FIG>).

Crosslinking reagents (or cross-linkers) suitable for making the crosslinks in the three-dimensional networks include those activated by ultraviolet light (e.g., long wave UV light), visible light, and heat. Exemplary cross-linkers activated by UV light include benzophenone, thioxanthones (e.g., thioxanthen-<NUM>-one, <NUM>-methylphenothiazine) and benzoin ethers (e.g., benzoin methyl ether, benzoin ethyl ether). Exemplary cross-linkers activated by visible light include ethyl eosin, eosin Y, rose bengal, camphorquinone and erythirosin. Exemplary cross-linkers activated by heat include <NUM>,<NUM>' azobis(<NUM>- cyanopentanoic) acid, and <NUM>,<NUM>-azobis[<NUM>-(<NUM>-imidazolin-<NUM>-yl) propane] dihydrochloride, and benzoyl peroxide. Other cross-linkers known in the art, e.g., those which are capable of forming radicals or other reactive groups upon being irradiated, may also be used.

The three-dimensional networks of the invention contain a plurality of channels.

As used herein, a "channel" is an elongated passage in a network that (<NUM>) is substantially straight, and (<NUM>) in the hydrated state of the network, has a minimum cross-section that is at least <NUM> and a length that is at least five times, and preferably at least ten times, the minimum cross-section of the passage. For example, the length of the channel can be <NUM> to <NUM> times, <NUM> to <NUM> times, or <NUM> to <NUM> times the minimum cross-section of the channel. A channel that is "substantially straight" is one which extends from a point of nucleation in one direction without changing direction more than <NUM> degrees in any direction, i.e., the X, Y or Z direction.

The "hydrated state of the network" means that the network is at equilibrium with respect to water absorption, i.e., it absorbs in aqueous solution as much water as it emits.

Channels can allow access to the interior of the network. Although channels can have a relatively large channel cross-section, the network can remain mechanically stable because the mesh size of the network can be significantly smaller than the channel cross-section. The channels can form a sort of highway, through which analytes can enter quickly into the interior of the network. The transport of the analytes can be effected in the channel by diffusion and/or convection.

The channels can extend from a surface or near the surface of the network into the interior of the network. For example, the one or more channels can extend from a point that is less than <NUM> microns, less than <NUM> microns, less than <NUM> microns, less than <NUM> microns, less than <NUM> microns, less than <NUM> microns, less than <NUM> microns, less than <NUM> microns, less than <NUM> microns, less than <NUM> micron from the surface of the network, or extends into the interior from a point on the surface of the network. The network contains a plurality of channels (e.g., <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>), each of which can extend from a surface or near a surface of the network into the interior of the network. In preferred embodiments, the network contains <NUM>, <NUM>, <NUM>, <NUM> or <NUM> channels, or a number of channels ranging between any two of the foregoing values (e.g., <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM> channels). In a specific preferred embodiment, the network contains <NUM> to <NUM> channels.

In some embodiments, the length of at least one channel is <NUM> to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM> to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM> to <NUM>%, or <NUM>% to <NUM>% of the largest dimension of the network. In preferred embodiments, the length of at least one channel is approximately <NUM>%, <NUM>%, <NUM>%, <NUM>% or <NUM>% of the largest dimension of the network, and in some embodiments has a length ranging between any pair of the foregoing embodiments (e.g., <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, or <NUM>% to <NUM>% of the largest dimension of the network). In a specific preferred embodiment, the length is <NUM>% to <NUM>% of the largest dimension of the network.

In some embodiments, the network comprises at least one channel having a minimum cross-section of at least <NUM> times, at least <NUM> times, at least <NUM> times, or at least <NUM> times the mesh size (e.g., <NUM> to <NUM> times, <NUM> to <NUM> times, <NUM> to <NUM> times, <NUM> to <NUM> times, <NUM> to <NUM> times, <NUM> to <NUM> times, <NUM> to <NUM> times, <NUM> to <NUM> times, <NUM> to <NUM> times, <NUM> to <NUM> times, <NUM> to <NUM> times, <NUM> to <NUM> times, <NUM> to <NUM> times, <NUM> to <NUM> times, <NUM> to <NUM> times, <NUM> to <NUM> times, <NUM> to <NUM> times, <NUM> to <NUM> times, or <NUM> to <NUM> times the network's mesh size). In preferred embodiments, the network comprises at least one channel having a minimum cross-section of <NUM> to <NUM> times the mesh size. This ensures a high stability of the polymer network, and can also prevent network penetration and binding by undesirable larger molecules or components in a sample.

The network can have a mesh size (measured in the hydrated state of the network) of, for example, <NUM> to <NUM> (e.g., <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>).

The networks of the invention comprise a plurality of channels (e.g., <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>), and each channel can independently have one or more of the features described in this section. In some embodiments, the majority of the channels have one or more features described in this section. In a specific preferred embodiment, the network contains <NUM> to <NUM> channels that each have one or more of the features described in this section.

The three-dimensional networks contain a plurality of channels that converge at a point located within the network, and are arranged such that, starting from the surface of the network towards the interior, the lateral distance between the channels decreases. In some embodiments, a plurality of channels extend approximately radially away from a point situated in the interior of the network. In some embodiments, the three-dimensional network contains multiple pluralities of channels (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> pluralities of channels), each plurality converging at a different point within the network. In certain aspects, a plurality (or each plurality) are connected at the point of their convergence.

The presence of a channel in a network can be verified using the following procedure:
The network is brought into contact with an aqueous liquid at room temperature, for example, in a bowl. The liquid contains a plurality of nanoparticles which are larger than the mesh size of the network and smaller than the minimum cross-section of the channel. Thus, nanoparticles can enter the channel and spread along the channel. Without being bound by theory, it is believed that this can occur due to the Brownian molecular motion and/or convection through the liquid in the channel. Such nanoparticles are known as quantum dots. They can, for example, have a diameter of about <NUM> nanometers.

An incubation period is selected so that the network in the liquid is completely hydrated, i.e., that the network on average takes the same amount of water as it releases. The incubation period can be, for example, one hour. The penetration of the nanoparticles in the channel can be accelerated by setting in motion the network and/or the liquid during the incubation, for example, by vibrating the network and/or liquid, preferably by means of ultrasonic waves.

After completion of the incubation, the liquid is separated from the network, for example, by draining the liquid from the bowl or taking the network out of the bowl.

Then, the hydrated network is frozen, for example, by means of liquid nitrogen. Thereafter, the frozen network can be cut with the aid of a cryomicrotome along mutually parallel cutting planes into thin slices. The cutting planes are arranged transversely to the longitudinal extension of the channel and penetrate the channel. The cutting is preferably carried out using a liquid nitrogen-cooled diamond blade. The thickness of the slices can be, for example, about <NUM> or <NUM>.

With the aid of a microscope, the nanoparticles disposed in the disks obtained by cutting the frozen network are located. The nanoparticles can be fluorescent and optically highlighted so that they can be better distinguished from the network, if necessary. The locating of the nanoparticles can be done using a suitable software with image processing methods. To examine the disks, preferably a confocal microscope laser scanning microscope with fluorescence optics or an electron microscope is used.

The geometry and/or position information of the nanoparticles obtained in this manner may be, with the aid of a computer, used to make a three-dimensional geometric model of distribution of the nanoparticles in the network. The model can then be used to determine whether the arrangement of the nanoparticles in the network comprises at least one substantially straight region whose cross-section is in no place smaller than <NUM> and whose length corresponds at least to the five-fold of its smallest cross-section. If this condition is fulfilled it is determined that the network comprises at least one channel.

Alternatively, the three-dimensional distribution of the nanoparticles can be determined in the network by means of micro-3D X-ray computer tomography.

A probe immobilized on the network of the disclosure can be a biomolecule or a molecule that binds a biomolecule, e.g., a partner of a specifically interacting system of complementary binding partners (receptor/ligand). For example, probes can comprise nucleic acids and their derivatives (such as RNA, DNA, locked nucleic acids (LNA), and peptide nucleic acids (PNA)), proteins, peptides, polypeptides and their derivatives (such as glucosamine, antibodies, antibody fragments, and enzymes), lipids (e.g., phospholipids, fatty acids such as arachidonic acid, monoglycerides, diglycerides, and triglycerides), carbohydrates, enzyme inhibitors, enzyme substrates, antigens, and epitopes. Probes can also comprise larger and composite structures such as liposomes, membranes and membrane fragments, cells, cell lysates, cell fragments, spores, and microorganisms.

A specifically interacting system of complementary bonding partners can be based on, for example, the interaction of a nucleic acid with a complementary nucleic acid, the interaction of a PNA with a nucleic acid, or the enzyme/substrate, receptor /ligand, lectin/sugar, antibody/antigen, avidin/biotin or streptavidin/biotin interaction.

Nucleic acid probes can be a DNA or an RNA, for example, an oligonucleotide or an aptamer, an LNA, PNA, or a DNA comprising a methacyrl group at the <NUM>' end (<NUM>' Acrydite™). Oligonucleotide probes can be, for example, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM> or <NUM> to <NUM> nucleotides long. In preferred embodiments, the oligonucleotide probe is <NUM> to <NUM> nucleotides in length.

When using a nucleic acid probe, all or only a portion of the probe can be complementary to the target sequence. The portion of the probe complementary to the target sequence is preferably at least <NUM> nucleotides in length, and more preferably at least <NUM>, at least <NUM> or at least <NUM> nucleotides in length. For nucleic acid probes of greater length than <NUM> or <NUM> nucleotides, the portion of the probe complementary to the target sequence can be at least <NUM>, at least <NUM> or at least <NUM> nucleotides in length.

The antibody can be, for example, a polyclonal, monoclonal, or chimeric antibody or an antigen binding fragment thereof (i.e., "antigen-binding portion") or single chain thereof, fusion proteins comprising an antibody, and any other modified configuration of the immunoglobulin molecule that comprises an antigen recognition site, including, for example without limitation, single chain (scFv) and domain antibodies (e.g., human, camelid, or shark domain antibodies), maxibodies, minibodies, intrabodies, diabodies, triabodies, tetrabodies, vNAR and bis-scFv (see e.g., <NPL>). An antibody includes an antibody of any class, such as IgG, IgA, or IgM (or sub-class thereof), and the antibody need not be of any particular class. Depending on the antibody amino acid sequence of the constant domain of its heavy chains, immunoglobulins can be assigned to different classes. There are five major classes of immunoglobulins: IgA, IgD, IgE, IgG, and IgM, and several of these may be further divided into subclasses (isotypes), e.g., IgG<NUM>, IgG<NUM>, IgG<NUM>, IgG<NUM>, IgA<NUM> and IgA<NUM>. "Antibody" also encompasses any of each of the foregoing antibody/immunoglobulin types.

Three-dimensional networks of the invention can comprise a single species of probe or more than one species of probe (e.g., <NUM>, <NUM>, <NUM>, or <NUM> or more species). Three-dimensional networks can comprise more than one species of probe for the same target (e.g., antibodies binding different epitopes of the same target) and/or comprise probes that bind multiple targets.

The networks can comprise a labeled (e.g., fluorescently labeled) control probe molecule that can be used, for example, to measure the amount probe present in the network.

The probes can be distributed throughout the network (e.g., on a surface and the interior of a network). Preferably, at least one probe is spaced away from the surface of the network and adjoins at least one channel. A probe so located is then directly accessible for analyte molecules or analyte components through the channel. In some embodiments, a majority of the probes are located in the interior of the network.

The one or more probes can be immobilized on the network covalently or non-covalently. For example, a probe can be crosslinked to the crosslinked polymer or a probe can be non-covalently bound to the network (such as by binding to a molecule covalently bound to the network). In a preferred embodiment, one or more probes are crosslinked to the crosslinked polymer. In some embodiments, a majority of the probes are covalently bound in the interior of the network (e.g., such that at least a portion of the probes adjoin a channel).

Without being bound by theory, the inventors believe that the processes described in Section <NUM> for manufacturing three-dimensional networks in the presence of salt crystals (particularly phosphate salt crystals) may result in a greater concentration of probe molecule at or near the interface between the polymer and the channel due to electrostatic interactions between the probe molecules (particularly nucleic acid probe molecules) and the salt crystals. Accordingly, in some embodiments of the invention, the disclosure provides networks according to the disclosure in which the probe density is greater at the interface between the polymer and the channels than within regions of the polymer not abutting a channel. In various embodiments, the probe density it at least <NUM>%, at least <NUM>%, at least <NUM>%, at least <NUM>%, or at least <NUM>% more dense at the interface between the polymer and the channels than within regions of the polymer not abutting a channel.

The density of probe molecule in a network can be verified using the following procedure:
The network is brought into contact with an aqueous liquid at room temperature, for example, in a bowl. The liquid contains a plurality of nanoparticles attached to a moiety that interacts with the probe molecules in the network, for example streptavidin if the probe molecules are biotinylated. The size of the nanoparticles is smaller than the mesh size of the network and smaller than the minimum cross-section of the channel to allow the nanoparticles to become distributed throughout the polymer. Suitable nanoparticles are quantum dots <NUM>-<NUM> nanometers in dimeter.

An incubation period is selected so that the network in the liquid is completely hydrated, i.e., that the network on average takes the same amount of water as it releases. The incubation period can be, for example, one hour. The penetration of the nanoparticles in the network can be accelerated by setting in motion the network and/or the liquid during the incubation, for example, by vibrating the network and/or liquid, preferably by means of ultrasonic waves.

The geometry and/or position information of the nanoparticles obtained in this manner may be, with the aid of a computer, used to make a three-dimensional geometric model of distribution of the nanoparticles in the network. The model can then be used to determine whether the distribution of nanoparticles reflects a greater density of probe molecules near sites of channels.

The three-dimensional networks of the disclosure can be positioned (e.g., deposited) on a substrate, and are preferably immobilized on a substrate (e.g., by covalent crosslinks between the network and the substrate). A plurality of networks can be immobilized on a substrate to form an array useful, for example, as a biochip.

Suitable substrates include organic polymers, e.g., cycloolefin copolymers (COCs), polystyrene, polyethylene, polypropylene and polymethylmethacrylate (PMMA, Plexiglas®). Ticona markets an example of a suitable COC under the trade name Topas®. Inorganic materiels (e.g., metal, glass) can also be used as a substrate. Such substrates can be coated with organic molecules to allow for crosslinks between the network and a surface of the substrate. For example, inorganic surfaces can be coated with self-assembled monolayers (SAMs). SAMs can themselves be completely unreactive and thus comprise or consist of, for example, pure alkyl silanes. Other substrates can also be suitable for crosslinking to the three-dimensional network provided they are able to enter into stable bonds with organic molecules during free-radical processes (e.g., organoboron compounds).

The substrate can be rigid or flexible. In some embodiments, the substrate is in the shape of a plate (e.g., a rectangular plate, a square plate, a circular disk, etc.). For example, the substrate can comprise a microwell plate, and the three-dimensional networks can be positioned in the wells of the plate.

The individual networks can be positioned at distinct spots on a surface of the substrate, e.g., in a matrix comprising a plurality of columns and rows. In the embodiment shown in <FIG>, the networks are located at <NUM> spots arranged in six columns and six rows. Arrays having different numbers of rows and columns, the number of each of which can be independently selected, are contemplated (e.g., <NUM> to <NUM> columns and <NUM> to <NUM> rows). The columns can be separated by a distance X and the rows can be separated by a distance Y (for example, as shown in <FIG>) so as to form a grid of spots on which the individual networks can be located. X and Y can be selected so that the networks, located at the spots of the grid, do not contact each other in the dehydrated state and do not contact each other in the hydrated state. The dimensions X and Y can be the same or different. In some embodiments, X and Y are the same. In some embodiments, X and Y are different. In some embodiments, X and Y are independently selected from distances of at least about <NUM> (e.g., <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>). In some embodiments, X and Y are both about <NUM>. In other embodiments, X and Y are both <NUM>.

In some embodiments, substrate is band-shaped (for example, as shown in <FIG>). The networks can be arranged as a single row extending in the longitudinal direction of a band-shaped organic surface, or can be arranged as multiple rows extending in the longitudinal direction of the band-shaped surface. The rows and columns in such band-shaped arrays can have grid dimensions X and Y as described above.

The individual networks can each cover an area of the surface of the array that is circular or substantially circular. Typically, the diameter of the area on the surface of the array covered by the individual networks (i.e., the spot diameter) is <NUM> to <NUM>. In various embodiments, the spot diameter is <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>, or selected from a range bounded by any two of the foregoing embodiments, e.g., <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>, and so on and so forth. In a preferred embodiment, the diameter ranges from <NUM> to <NUM> or a subrange thereof.

The arrays of the invention typically have at least <NUM> individual three-dimensional networks. In certain aspects, the arrays have at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, or at least <NUM> individual three-dimensional networks. In some embodiments, the arrays of the disclosure have <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM> individual networks, or have a number of three-dimensional networks selected from a range bounded any two of the foregoing embodiments, e.g., from <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM> three-dimensional networks, and so on and so forth. In a preferred embodiment, number of three-dimensional networks on an array ranges from <NUM> to <NUM>. In a particularly preferred embodiment, the number of three-dimensional networks on an array ranges from <NUM> to <NUM>.

The individual networks which comprise the arrays of the disclosure can have identical or different probes (e.g., each network can have a unique set of probes, multiple networks can have the same set of probes and other networks can have a different set or sets of probes, or all of networks can have the same set of probes). For example, networks arranged in the same row of a matrix can comprise the same probes and the networks arranged in different rows of the matrix can have different probes.

Typically, the individual networks on an array vary by no more than <NUM>%, no more than <NUM>%, no more than <NUM>% or no more than <NUM>% from one another by spot diameter and/or network volume.

In some embodiments, the arrays comprise one or more individual networks (e.g., spots on an array) with one or more control oligonucleotides or probe molecules. The control oligonucleotides can be labelled, e.g., fluorescently labelled, for use as a spatial control (for spatially orienting the array) and/or a quantifying the amount of probe molecules bound to the networks, for example, when washing and reusing an array of the disclosure (i.e., as a "reusability control"). The spatial and reusability control probes (which can be the same or different probes) are referred to in Section <NUM> as a "landing light", where the same probe is used for both purposes.

The same spot on the array or a different spot on the array can further include an unlabelled probe that is complementary to a known target. When used in a hybridization assay, determining the signal strength of hybridization of the unlabelled probe to the labelled target can determine the efficiency of the hybridization reaction. When an individual network (i.e., a spot on an array) is used both as a reusability and/or spatial control and a hybridization control, a different fluorescent moiety can be used to label the target molecule than the fluorescent moiety of the reusability control or spatial control probes.

In some embodiments, the arrays of the invention can be reused at least <NUM> times, at least <NUM> times, at least <NUM> times, at least <NUM> times, at least <NUM> times, or at least <NUM> times (e.g., <NUM> to <NUM> times, <NUM> to <NUM> times, <NUM> to <NUM> times, <NUM> to <NUM> times, <NUM> to <NUM> times, <NUM> to <NUM> times, or <NUM> to <NUM> times, preferably comprising reusing the array <NUM> to <NUM> times). The array can be washed with a salt solution under denaturating conditions (e.g., low salt concentration and high temperature). For example, the array can be washed with a <NUM>-<NUM> phosphate buffer at <NUM>-<NUM> between uses. The temperature of the wash can be selected based upon the length (Tm) of the target:probe hybrid.

The integrity of an array can be determined by a "reusability control" probe. The reusability control probe can be fluorescently labeled or can be detected by hybridization to a fluorescently labeled complementary nucleic acid. The fluorescent label of a fluorescently labeled reusability control probe may be bleached by repeated excitation, before the integrity of the nucleic acid is compromised; in such cases any further reuses can include detection of hybridization to a fluorescently labeled complementary nucleic acid as a control. Typically, an array of the invention is stable for at least <NUM> months.

In various embodiments, a fluorescently labeled reusability control probe retains at least <NUM>%, <NUM>% <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>% of its initial fluorescence signal strength after <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> uses. Preferably, the reusability control probe retains least <NUM>% of its fluorescence signal strength after <NUM> or <NUM> uses. An array can continue to be reused until the reusability control probe retains at least <NUM>% of its fluorescence signal strength, for example after <NUM>, <NUM>, <NUM> or <NUM> reuses. The fluorescent signal strength of the control probe can be tested between every reuse, every other reuse, every third reuse, every fourth reuse, every fifth reuse, every sixth reuse, every seventh reuse, every eighth reuse, every ninth reuse, every tenth reuse, or a combination of the above. For example, the signal strength can be tested periodically between <NUM> or <NUM> reuses initially and the frequency of testing increased with the number of reuses such that it is tested after each reuse after a certain number (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM>) uses. In some embodiments, the frequency of testing averages once per <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM> uses, or averages within a range bounded between any two of the foregoing values, e.g., once per <NUM>-<NUM> uses, once per <NUM>-<NUM> uses, once per <NUM>-<NUM> uses, or once per <NUM>-<NUM> uses.

It is noted that the nomenclature of "spatial control", "reusability control" and "hybridization control" is included for convenience and reference purposes and is not intended to connote a requirement that the probes referred to "spatial control", "reusability control" and "hybridization control" be used as such.

In one aspect, the processes of the invention for making three-dimensional polymer networks comprise (a) exposing a mixture comprising an aqueous salt solution, a polymer, a cross-linker and probes to salt crystal forming conditions, (b) exposing the mixture to crosslinking conditions to crosslink the polymer for form a crosslinked polymer network, and (c) contacting the crosslinked polymer network with a solvent to dissolve the salt crystals and form one or more channels.

The processes can further comprise a step of forming the mixture by combining an aqueous salt solution, a polymer, a cross-linker and probes, and/or further comprise a step of applying the mixture to a substrate (e.g., a substrate described in Section <NUM>) prior to exposing the mixture to salt forming conditions. If the polymer being used has a pre-attached cross-linker (e.g., when using a copolymer polymerized from a monomer comprising a cross-linker), the step of forming the mixture can comprise combining an aqueous salt solution with the polymer and, optionally, one or more probes.

The channels formed by dissolution of the salt crystals can have one or more of the features described in Section <NUM>.

The mixture can be applied to a substrate prior to exposing the mixture to salt forming conditions for example, by spraying the mixture onto a surface of the substrate (e.g., at <NUM> sites on the surface). The mixture can be applied to the surface using a DNA chip spotter or inkjet printer, for example. In a preferred embodiment, the mixture is sprayed using an inkjet printer. This permits a simple and rapid application of the mixture to a large number of spots on the substrate. The spots can be arranged, for example, in the form of a matrix in several rows and/or columns. Preferably, the salt content in the mixture during printing is below the solubility limit so that the mixture does not crystallize in the printing head of the printer. The volume of mixture applied at individual spots can be, for example, <NUM> pl, <NUM> pl, <NUM> pl, <NUM> pl, <NUM> pl, <NUM> pl, <NUM> nl, <NUM> nl, <NUM> nl, <NUM> nl, or <NUM> nl, or can be selected from a range bounded by any two of the foregoing values (e.g., <NUM> pl to <NUM> nl, <NUM> pl to <NUM> nl, <NUM> pl to <NUM> nl, <NUM> pl to <NUM> nl, <NUM> pl to <NUM> pl, <NUM> pl to <NUM> nl, <NUM> pl to <NUM> nl <NUM> nl to <NUM> nl, and so on and so forth). In preferred embodiments, the spot volume is <NUM> pl to <NUM> nl.

The diameter of the individual spots will depend on the composition of the mixture, the volume of the mixture applied, and the surface chemistry of the substrate. Spot diameters typically range between <NUM> to <NUM> and can be obtained by varying the foregoing parameters. In various embodiments, the spot diameters are <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>, or selected from a range bounded by any two of the foregoing embodiments, e.g., <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>, and so on and so forth. In a preferred embodiment, the diameter ranges from <NUM> to <NUM> or a subrange thereof.

Suitable polymers, cross-linkers, and probes that can be used in the processes of the disclosure are described in Sections <NUM>. <NUM>, <NUM>. <NUM>, and <NUM>. <NUM>, respectively. In some embodiments, the polymer used in the processes has at least one cross-linker group per polymer molecule. In a preferred embodiment, the polymer has at least two cross-linker groups per molecule. In a particularly preferred embodiment, the polymer has at least two photoreactive cross-linker groups per molecule. In these embodiments, separate polymer and cross-linker molecules are not needed.

Suitable salts that can be included in the mixture are described in Section <NUM>. Suitable salt forming conditions are described in Section <NUM>. Suitable crosslinking conditions are described in Section <NUM>. Suitable solvents for dissolving the salt crystals are described in Section <NUM>.

The salt can be selected for its compatibility with one or more probes. Ideally, the salt has one or more of the following characteristics, (i) the salt is not toxic to the probes (e.g., the salt does not denature the probes), (ii) the salt does not react chemically with the probes, (iii) the salt does not attack fluorophores, such as cyanine dyes, which are suitable for the optical marking of probes, (iv) the salt does not react with analytes, detection molecules, and/or binding partners bonded thereto, and/or (v) the salt forms needle-shaped crystals.

In a preferred embodiment, the salt solution comprises monovalent cations. The mixture can comprise disodium hydrogen phosphate and/or sodium dihydrogen phosphate which, in aqueous solution, releases Na+ cations and phosphate ions PO<NUM><NUM>-. Sodium phosphate is readily soluble in water and forms colorless crystals.

In a particularly preferred embodiment, the mixture comprises dipotassium hydrogen phosphate (K<NUM>HPO<NUM>) and/or potassium dihydrogen phosphate (KH<NUM>PO<NUM>). These salts are excellently soluble in water and can therefore form a correspondingly large number of needle-shaped salt crystals in the mixture.

Salt crystal forming conditions can comprise forming in the mixture at least one salt crystal, preferably a needle-shaped salt crystal, by dehydrating the mixture or cooling the mixture until the relative salt content in the mixture increases to above the solubility limit, meaning that the mixture is supersaturated with the salt. This promotes the formation of salt crystals from a crystallization germ located in the volume of the mixture towards the surface of the mixture.

The mixture can be dehydrated by heating the mixture, exposing the mixture to a vacuum, and/or reducing the humidity of the atmosphere surrounding the mixture.

The mixture can be heated by placing the mixture on a heated substrate or surface (e.g., between about <NUM> to about <NUM>), heating the substrate or surface on which the mixture has been placed (e.g., to between about <NUM> to about <NUM>), and/or contacting the mixture with a hot gas (e.g., air, nitrogen, or carbon dioxide having a temperature that is higher than the temperature of the mixture) such that water is evaporated from the mixture. The contacting with the hot gas can, for example, take place by placing the mixture in a heating oven. During the transportation to the heating oven, the mixture is preferably kept moist, in particular at a relative humidity of above <NUM>%. As a result of this, an uncontrolled formation of salt crystals during the transportation of the mixture to the heating oven is counteracted. This permits the formation of longer, needle-shaped salt crystals in the heating oven. By heating the mixture it is also possible to activate thermally activatable cross-linkers, if present, and crosslink the polymer thereby.

In some embodiments, the temperature of the heated substrate and/or air used to dehydrate the mixture is <NUM> or more above the temperature of the mixture before heating the mixture, but less than <NUM>.

The mixture can be cooled by placing the mixture on a cooled substrate or surface (e.g., between about <NUM> to about <NUM>), cooling the substrate or surface on which the mixture has been placed (e.g., to between about <NUM> to about <NUM>) and/or bringing it into contact with a cold gas (e.g., air, nitrogen, or carbon dioxide having a temperature that is lower than the temperature of the mixture). When cooled, the temperature-dependent solubility limit of the salt in the mixture decreases until the mixture is ultimately supersaturated with the salt. The formation one or more salt crystals, preferably needle-shaped, is promoted by this. In some embodiments, the mixture is cooled by incubating it in a cold chamber with low humidity (e.g., temperatures between <NUM> and <NUM>, relative humidity < <NUM>%).

The temperature in the mixture is preferably held above the dew point of the ambient air surrounding the mixture during the formation of the one or more salt crystals. This prevents the mixture becoming diluted with water condensed from the ambient air, which could lead to a decrease in the relative salt content in the mixture.

The crosslinking conditions can be selected based upon the type of cross-linker used. For example, when using a cross-linker activated by ultraviolet light (e.g., benzophenone, a thioxanthone or a benzoin ether), the crosslinking conditions can comprise exposing the mixture to ultraviolet (UV) light. In some embodiments, UV light having a wavelength from about <NUM> to about <NUM> is used (e.g., <NUM> ±<NUM> or <NUM> ±<NUM>). The use of lower energy/longer wavelength UV light (e.g., <NUM> UV light vs. <NUM> UV light) can require longer exposure times. When using a cross-linker activated by visible light (e.g., ethyl eosin, eosin Y, rose bengal, camphorquinone or erythirosin), the crosslinking conditions can comprise exposing the mixture to visible light. When using a thermally activated cross-linker (e.g., <NUM>,<NUM>' azobis(<NUM>- cyanopentanoic) acid, and <NUM>,<NUM>-azobis[<NUM>-(<NUM>-imidazolin-<NUM>-yl) propane] dihydrochloride, or benzoyl peroxide), the crosslinking conditions can comprise exposing the mixture to heat.

The length and intensity of the crosslinking conditions can be selected to effect crosslinking of polymer molecules to other polymer molecules, crosslinking of polymer molecules to probe molecules (if present), and crosslinking of polymer molecules to substrate molecules or organic molecules present on the substrate (if present). The length and intensity of crosslinking conditions for a mixture containing probes can be determined experimentally to balance robustness of immobilization and nativity of probe molecules, for example.

After crosslinking the polymer, the one or more salt crystals can be dissolved in the solvent in such a way that at least one channel is formed in the network, said channel extending starting from the surface and/or near the surface of the network into the interior of the network. Advantageously, after the salt crystals have dissolved in a solvent, a hollow, elongated channel is produced in the place where the salt crystal was, according to the principle of the "lost" form. The channels allow analytes to penetrate through the channel into the interior of the network and specifically bind a probe located in the interior of the network. When using an array produced by the method of the disclosure as a biological sensor, a high measurement accuracy and high measurement dynamic are permitted.

The solvent for dissolving the one or more salt crystals can be chosen in such a way that it is compatible to the polymer and probes, if present (e.g., the solvent can be chosen such that it does not dissolve the polymer and probes). Preferably, the solvent used is a water based buffer, such as diluted phosphate buffer. Methanol, ethanol, propanol or a mixture of these liquids can be added to the buffer to facilitate the removal of unbound polymer from the network.

After the removal of the salt crystals the network can collapse due to drying and can be rehydrated. Drying the network has advantages for shipping and stabilization of probe biomolecules.

The networks and arrays of the invention can be used to determine the presence or absence of an analyte in a sample, preferably a liquid sample. The disclosure therefore provides methods for determining whether an analyte is present in a sample or plurality of samples, comprising contacting a network or array of the disclosure comprising probe molecules that are capable of binding to the analyte with the sample or plurality of samples and detecting binding of the analyte to the probe molecules, thereby determining whether the analyte is present in the sample or plurality of samples. When arrays comprising different species of probes capable of binding different species of analyte are used in the methods, the presence of the different species of analytes can be determined by detecting the binding of the different species of analytes to the probes. In some embodiments, the methods further comprise a step of quantifying the amount of analyte or analytes bound to the array.

The analyte can be, for example, a nucleic acid, such as a polymerase chain reaction (PCR) amplicon. In some embodiments, the PCR amplicon is amplified from a biological or environmental sample (e.g., blood, serum, plasma, tissue, cells, saliva, sputum, urine, cerebrospinal fluid, pleural fluid, milk, tears, stool, sweat, semen, whole cells, cell constituent, cell smear, or an extract or derivative thereof). In some embodiments, the nucleic acid is labeled (e.g., fluorescently labeled).

An analyte placed on the surface of the network can penetrate into the interior of the network through the channel in order to specifically bind to a probe (e.g., a biomolecule) covalently bonded there to the polymer. When using the arrays of the disclosure with the networks immobilized thereon as biological sensor, a high measurement accuracy and also a high measurement dynamic is permitted.

The networks and arrays of the disclosure can be regenerated after use as a biosensor and can be used several times (e.g., at <NUM> times, at least <NUM> times, at least <NUM> times, at least <NUM> times, at least <NUM> times, or at least <NUM> times). If the probe molecules are DNA, this can be achieved, for example, by heating the network(s) in an 1x phosphate buffered saline to a temperature between <NUM> and <NUM> for about <NUM> minutes. Then, the phosphate buffered saline can be exchanged for a new phosphate buffered saline to wash the denatured DNA out of the network(s). If the probe molecules of the network(s) or array are antigens the network(s) or array can be regenerated by bringing the network(s) into contact with <NUM> N NaOH for about <NUM> minutes. Then, the <NUM> N NaOH can be exchanged for a phosphate buffered saline to wash the antigens out of the network. Thus, some embodiments of the methods of using the networks and arrays of the disclosure comprise using a network or array that has been washed prior to contact with a sample or a plurality of samples.

Because the arrays of the invention achieve economical determination of the qualitative and quantitative presence of nucleic acids in a sample, it has immediate application to problems relating to health and disease in human and non-human animals.

In these applications a preparation containing a target molecule is derived or extracted from biological or environmental sources according to protocols known in the art. The target molecules can be derived or extracted from cells and tissues of all taxonomic classes, including viruses, bacteria and eukaryotes, prokaryotes, protista, plants, fungi, and animals of all phyla and classes. The animals can be vertebrates, mammals, primates, and especially humans. Blood, serum, plasma, tissue, cells, saliva, sputum, urine, cerebrospinal fluid, pleural fluid, milk, tears, stool, sweat, semen, whole cells, cell constituent, and cell smears are suitable sources of target molecules.

The target molecules are preferably nucleic acids amplified (e.g., by PCR) from any of the foregoing sources).

The arrays of the invention can include probes that are useful to detect pathogens of humans or non-human animals. Such probes include oligonucleotides complementary at least in part to bacterial, viral or fungal targets, or any combinations of bacterial, viral and fungal targets.

The arrays of the invention can include probes useful to detect gene expression in human or non-human animal cells, e.g., gene expression associated with a disease or disorder such as cancer, cardiovascular disease, or metabolic disease for the purpose of diagnosing a subject, monitoring treatment of a subject or prognosis of a subject's outcome. Gene expression information can then track disease progression or regression, and such information can assist in monitoring the success or changing the course of an initial therapy.

The following exemplary protocols, which refer to the reference numbers provided in the figures, are within the scope of the disclosure and can be used in conjunction with the polymers, cross-linkers and probes of Sections <NUM>. <NUM>, <NUM>. <NUM> and <NUM>. <NUM>, respectively. Further useful polymers (including co-polymers) and cross-linker groups for use in the following methods are described in <NPL> and in <CIT>. In one embodiment, a polymer mixture according to Section <NUM> is used.

A plate with an organic surface (<NUM>) is placed on a heated holder (<NUM>). Temperatures between <NUM> and <NUM> are suitable. A mixture (<NUM>) containing a polymer (<NUM>), probe biomolecules (<NUM>) and an aqueous salt solution is spotted on the organic surface (<NUM>) using a standard DNA chip spotter (e.g., Scienion, Germany). Volumes of <NUM> to <NUM> nl are printed on each spot (<NUM>) (see, <FIG>). The liquid of these spots dries almost immediately leading to a very fast nucleation of salt crystals (<NUM>). After nucleation, needle-shaped salt crystals can extend from at least one crystallization germ (<NUM>) located in the volume of the mixture (<NUM>) to the surface (<NUM>) of the mixture (<NUM>) (see, <FIG>). After nucleation of the crystals (<NUM>) the spots (<NUM>) are irradiated in a UV cross-linker immediately with optical UV radiation (<NUM>) (see, <FIG>) such that the probe biomolecules (<NUM>) are covalently bonded to the polymer (<NUM>), and the polymer (<NUM>) is covalently bonded to the organic surface (<NUM>) and crosslinked (see, <FIG>). Care is taken that the dried, crosslinked mixture (<NUM>) is not attracting moisture to become liquid again.

The dried, crosslinked mixture (<NUM>) is then brought into contact with a solvent (<NUM>) for the crystals (<NUM>) such that at the places at which the crystals (<NUM>) were, channels (<NUM>) are formed in the network (<NUM>) comprising the polymer (<NUM>) and the probe biomolecules (<NUM>) (see, <FIG>). Thereafter, the solvent (<NUM>) is removed. The channels (<NUM>) can extend from the surface (<NUM>) of the network (<NUM>) into the interior of the network (<NUM>). The solvent (<NUM>) in which the salt crystals (<NUM>) are dissolved is chosen in such a way that it is compatible to the probe biomolecule (<NUM>) and also the polymer (<NUM>). Preferably, the solvent (<NUM>) used is water based.

A mixture (<NUM>) containing a polymer (<NUM>), probe biomolecules (<NUM>) and an aqueous salt solution is spotted on an organic surface (<NUM>) arranged on a plate using a standard DNA chip spotter (e.g., Scienion, Germany). Volumes of <NUM> to <NUM> nl are printed on each spot <NUM> (see, <FIG>). The plate with the spots (<NUM>) on the organic surface (<NUM>) is placed on a chilled holder (<NUM>) (see, <FIG>). Temperatures between <NUM> and <NUM> are suitable. The liquid of these spots is cooled down to reach an over saturation of the buffer that almost immediately leads to a nucleation of crystals. After nucleation needle-shaped salt crystals (<NUM>) can extend from at least one crystallization germ (<NUM>) located in the volume of the mixture (<NUM>) to the surface (<NUM>) of the mixture (<NUM>). After printing these targets are put in an oven (e.g., at <NUM>) for complete drying. After nucleation of the crystals the spots are irradiated in a UV cross-linker immediately with optical UV radiation (<NUM>) (see, <FIG>) such that the probe biomolecules (<NUM>) are covalently bonded to the polymer (<NUM>), and the polymer (<NUM>) is covalently bonded to the organic surface (<NUM>) and crosslinked. Care is taken that the dried, crosslinked mixture is not attracting moisture to become liquid again.

The dried, crosslinked mixture (<NUM>) is then brought into contact with a solvent (<NUM>) to dissolve the crystals (<NUM>) such that at the places at which the crystals (<NUM>) were, channels (<NUM>) are formed in the network (<NUM>) comprising the polymer (<NUM>) and the probe biomolecules (<NUM>). Thereafter, the solvent (<NUM>) is removed. The channels (<NUM>) can extend from the surface (<NUM>) of the network (<NUM>) into the interior of the network (<NUM>). The solvent (<NUM>) in which the salt crystals (<NUM>) are dissolved is chosen in such a way that it is compatible with the probe biomolecule (<NUM>) and the polymer (<NUM>). Preferably, the solvent (<NUM>) used is water based.

As can be seen in <FIG> a plurality of channels (<NUM>) can be formed in the network (<NUM>). The channels (<NUM>) can extend from the surface (<NUM>) of the network (<NUM>) to at least one point located within the network (<NUM>). The channels (<NUM>) can be arranged in such a way that - starting from the surface (<NUM>) in the direction of the interior - the lateral distance between the channels (<NUM>) decreases.

A mixture (<NUM>) containing a polymer (<NUM>), probe biomolecules (<NUM>) and an aqueous salt solution is printed on an organic surface (<NUM>) of a plate at normal conditions with a humidity ranging from <NUM> - <NUM>%, preferably <NUM>-<NUM>%. The mixture can be near saturation, <NUM> sodium phosphate, pH <NUM>, for example. Volumes of <NUM> to <NUM> nl are printed on each spot (<NUM>). The moisture content in the print compartment makes sure the spots (<NUM>) stay liquid without crystal formation (i.e., no nucleation takes place). The plate is then put in a container, a cardboard box for example. Lids are put on the plate having the organic surface (<NUM>) for transport. The plate with the spots (<NUM>) on the organic surface (<NUM>) is then put in a drying oven or on a hot plate to rapidly cause nucleation such that needle-shaped salt crystals (<NUM>) extend from at least one crystallization germ (<NUM>) located in the volume of the mixture toward the surface <NUM> of the mixture (<NUM>).

The temperature of the oven / hot plate should be <NUM> or more above the printing temperature. Temperatures above <NUM> are not necessary.

After drying, the mixture is irradiated to crosslink the polymer (<NUM>), probe biomolecules (<NUM>), and organic surface (<NUM>).

The dried, crosslinked mixture (<NUM>) is then brought into contact with a solvent (<NUM>) such that at the places at which the crystals (<NUM>) were, channels (<NUM>) are formed in the network (<NUM>) comprising the polymer (<NUM>) and the probe biomolecules (<NUM>). Thereafter, the solvent (<NUM>) is removed. The channels (<NUM>) can are extend from the surface (<NUM>) of the network (<NUM>) into the interior of the network (<NUM>). The solvent (<NUM>) in which the salt crystals (<NUM>) are dissolved is chosen in such a way that it is compatible with the probe biomolecules (<NUM>) and the polymer (<NUM>). Preferably, the solvent (<NUM>) used is water based.

Alternatively, a plate with spots (<NUM>) on the organic surface (<NUM>) prepared as in exemplary protocol <NUM> can be cooled to achieve nucleation by putting in a cold chamber with low humidity (e.g., temperatures < <NUM>, relative humidity < <NUM>%). The drying can be performed by reducing the humidity or by applying a vacuum after nucleation has started. After nucleation, needle-shaped salt crystals (<NUM>) can extend from at least one crystallization germ (<NUM>) located in the volume of the mixture (<NUM>) toward the surface (<NUM>) of the mixture (<NUM>). The plate with the spots (<NUM>) on the organic surface (<NUM>) is put in an oven at <NUM>°-<NUM> for <NUM> hour to fully dry the spots. The spots (<NUM>) are UV irradiated with <NUM> J @ <NUM> in a UV cross-linker, i.e. Stratalinker <NUM>. To do this, the plate with the spots (<NUM>) on the organic surface (<NUM>) can be put into the center of the chamber with the shorter side parallel to the door of the chamber. Then, the cover is removed and the cross-linker is started. When machine is finished the array is removed and the cover is replaced.

Alternatively, other UV cross-linkers with the same wavelength (<NUM>-<NUM>, for example) or longer wavelengths, e.g., <NUM>, can be used.

The mixture (<NUM>) is then brought into contact with a solvent (<NUM>) to dissolve the crystals (<NUM>) such that at the places at which the crystals (<NUM>) were, channels (<NUM>) are formed in the network (<NUM>) comprising the polymer (<NUM>) and the probe biomolecules (<NUM>). Thereafter, the solvent (<NUM>) is removed. The channels (<NUM>) can extend from the surface (<NUM>) of the network (<NUM>) into the interior of the network (<NUM>). The solvent (<NUM>) in which the salt crystals (<NUM>) are dissolved is chosen in such a way that it is compatible with the probe biomolecules (<NUM>) the polymer (<NUM>). Preferably, the solvent (<NUM>) used is water based.

A <NUM>/ml polymer stock solution is prepared by dissolving <NUM> of the crosslinking polymer poly(dimethylacrylamide) co <NUM>% methacryloyloxybenzophenone co <NUM>% Sodium <NUM>-vinylbenzenesulfonate in <NUM> of DNAse free water. This is achieved by vigorous shaking and vortexing for approximately <NUM> minutes until all the visible polymer is dissolved. The stock solution is then wrapped in foil to protect it from light and placed in a refrigerator overnight to ensure the polymer completely dissolves and to allow the foam to reduce. The polymer has at least two photoreactive groups per molecule.

A mixture comprising the polymer, DNA oligonucleotide probes, and sodium phosphate is made by mixing <NUM>µl of a <NUM> DNA oligonucleotide stock solution, <NUM>µl of the <NUM>/ml polymer stock solution (to provide a concentration of polymer in the mixture of <NUM> / ml), and <NUM>µl of a <NUM> sodium phosphate buffer, pH <NUM>.

The mixture is used to prepare a three-dimensional network of the invention using the method of any one of Exemplary Protocols <NUM> through <NUM>.

Oligonucleotides for immobilization were dissolved at a concentration of <NUM> in a <NUM> sodium phosphate buffer, pH <NUM> containing <NUM>/ml of the photoreactive polymer described in Example <NUM>. Each oligonucleotide had a length of <NUM>-<NUM> nucleotides complementary to the target DNA and a tail of <NUM> thymidines (for a total oligonucleotide length of <NUM>-<NUM> nucleotides).

The mixture was used to print the following spots on an organic surface of a plate to provide an array:.

In order to avoid the formation of salt crystals on the source plate (i.e., the plate from which the mixture was taken) this plate was kept at ambient temperature (<NUM>).

A Greiner <NUM> well plate with a flat crystal clear bottom with an organic surface was cooled to <NUM> to avoid drying out of the printed spots. Using a Scienion® SciFlex <NUM> printer with a PDC <NUM> nozzle <NUM> drops per spot were printed on the organic surface, resulting in a spot volume of approx. The humidity of the printer was kept at <NUM>-<NUM>% relative humidity.

After the print the size of the spots was checked by an automated head camera on the print head to assure that no drying in or crystal formation has taken place in the spots. All spots were still wet and have the same size. No crystal formation was visible.

The <NUM> well plate was then sealed with a lid to avoid drying in and immediately put on a hot plate (<NUM>) in a drying oven to perform crystal initiation and drying of the spots.

After <NUM> hr incubation at <NUM> to ensure proper drying of the spots the plate was irradiated with 1J @ <NUM> in a Stratalinker® <NUM>.

A procedure similar to that described in Section <NUM>. <NUM> was used but the target plate was kept at ambient temperature substantially as described by <NPL>. After the print, some spots showed a reduced size, i.e., some of the spots in random places in the array were dried in and exhibited phase separation immediately after the printing. The plate was then taken out of the printer and taken to the sample drying process as described above with no lid on, upon which further drying in occurred.

Before use the plates were washed in a plate washer for <NUM> times with <NUM>µl of wash buffer (<NUM> sodium phosphate pH <NUM>) and then the buffer was exchanged to <NUM> sodium phosphate pH <NUM>. The plates were heated for <NUM> minutes at <NUM> on a heater shaker to extract unbound DNA and polymer. The buffer then was exchanged to <NUM> sodium phosphate buffer using an automated <NUM> well plate washer.

A mix of <NUM> Cy5-labeled PCR product and <NUM> sodium phosphate buffer (<NUM>, pH7) was incubated on the arrays for <NUM> minutes at <NUM> and <NUM> minutes at <NUM> on heater shaker. Afterward the plates were washed with <NUM> sodium phosphate buffer pH7 for three times in <NUM> well plate washer. Plates with buffer were scanned in Sensovation® Flair reader and the spot intensity of the different spots was measured.

<NUM> arrays produced by the method of Section <NUM>. <NUM> and <NUM> arrays produced by the method of Section <NUM>. <NUM> were analysed and the data processed in a spreadsheet program. Mean and standard error of the mean (SEM) were calculated and compared. Results are shown in <FIG>.

Several arrays were prepared according to the procedure described in Section <NUM>. <NUM>, including a "landing light" spot containing fluorescently labeled oligonucleotides. The arrays were reused in hybridization assays and washed according to the following procedure in between hybridizations:.

Claim 1:
A three-dimensional network having a surface and an interior, said three-dimensional network:
(a) is composed of a water-swellable polymer formed by crosslinking water soluble polymer chains;
(b) is crosslinked to the surface of a substrate; and
(c) comprises probe molecules covalently attached to the polymer chains, characterized in that
(i) said network comprises a plurality of channels that converge at a point in the interior of the network such that the lateral distance between the channels decreases from the surface toward the point in the interior; and
(ii) a majority of the probe molecules are immobilized in the interior of the network and at least a portion of the probe molecules adjoin a channel.