Hydrogel microarrays

C. R., Fabrication and characterization of 3D hydrogel microarrays to measnre antigenicity and antibody functionality for biosensor applications. Biosens. Bioelectron., 20(4), 753-764, 2004. 

In 2008, inkjet printing was used to elaborate hydrogel microarrays (73,74). The polymer hydrogel microarrays were fabricated from monomers and initiator, allowing up to 1800 individual polymer features to be printed on a single glass slide. 

In contrast to high density arrays low density arrays are made by deposition of pre-synthesized oligonucleotides or proteins on activated surfaces. There are several printing techniques for fabricating microarrays Non-contact biochip arrayers, commonly based on the piezoelectric effect, can apply controlled sub-nanoliter probe volumes to pre-specified locations on the chip surface. Due to the fact that the dispenser does not touch the surface, a non-contact arrayer provides low risk of contamination and is most suitable for printing on soft materials such as hydrogels. 

Gurevitch, D., Dong, X.F., Pircher, T.J., Matsumoto, S.S., Roycroft, P, Tsinber, R, Falcovitz, Y.Ff., and Flahn, S., A novel three-dimensional hydrogel-based microarray platform, JALA, 6, 87-91, 2001. 

Motorola Life Sciences and Packard Biosciences (now Perkin Elmer Life Sciences) established a development partnership with ANL to commercialize the technology in 1998 but later abandoned the technology in favor of the SurModics hydrogel introduced in 1999 (3D-Link ). Motorola introduced the CodeLink microarray product based upon the SurModics PhotoLink chemistry. Amersham Biosciences acquired Motorola s biochip business in 2002 and now offers CodeLink microarrays. Perkin Elmer sells a similar product under the trade name of HydroGel 3D. 

In protein microarrays, capture molecules need to be immobilized in a functional state on a solid support. In principle, the format of the assay system does not limit the choice of appropriate surface chemistry. The same immobilization procedure can be applied for both planar and bead-based systems. Proteins can be immobilized on various surfaces (Fig. 1) (12). Two-dimensional polystyrene, polylysine, aminosilane, or aldehyde, epoxy- or thiol group-coated surfaces can be used to immobilize proteins via noncovalent or covalent attachment (13,14). Three-dimensional supports like nitrocellulose or hydrogel-coated surfaces enable the immobilization of the proteins in a network structure. Larger quantities of proteins can be immobilized and kept in a functional state. Affinity binding reagents such as protein A, G, and L can be used to immobilize antibodies (15), streptavidin is used for biotinylated proteins (16), chelate for His-tagged proteins (17, 18), anti-GST antibodies for GST fusion proteins (19), and oligonucleotides for cDNA or mRNA-protein hybrids (20). 

Key words Protein microarray, Hydrogel, Immobilization, SPR, Protein-protein interaction... 

Y. Zhou, O. Andersson, P. Lindberg and Liedberg, B. (2004) Protein microarrays on carboxymethylated dextran hydrogels immobilization, characterization and application. Microchim. Acta., 147, 21-30. 

Koh, W.-G., Itle, L. J., Pishko, M. V., Molding of hydrogel microstructures to create multiphenotype cell microarrays. Anal. Chem, 2003, 75, 5783-5789. 

Dyukova VI, Dementieva El, Zubtsov DA, Galanina OE, Bovin NV, Rubina AY. Hydrogel glycan microarrays. Anal. Biochem. 2005 347 94-105. 

Alexeev VL, Das S, Finegold DN, Asher SA (2004) Photonic crystal glucose-sensing material for noninvasive monitoring of glucose in tear fluid. Clin Chem 50(12) 2353-2360 Allcock HR, Phelps MVB, Barrett EW, Pishko MV, Koh WG (2006) Ultraviolet photolithographic development of polyphosphazene hydrogel microstructures for potential use in microarray biosensors. Chem Mater 18(3) 609-613... 

Figure 3.8 The most frequently used methods to immobilize capture molecules onto microarray surfaces. (A) Antibody adsorption by poly-L-lysine-, nitrocellulose-, or polyvinylidene fluoride-treated surface. (B) Covalent binding using various silane reagents of APTES (3-aminopropyl)triethoxysilane, GPTS (3-gly-cidoxypropyl)trimethoxysilane, and MPTS (3-mercaptopropyl)trimethoxysilane. (C) Affinity interactions by biotin/streptavidine or histidine-tag/nickel-nitrilotri-acetic acid. (D) Diffusion-based (hydrogel) antibody-immobilization technique.

Alternatively, each molecule can be attached to the carrier material (e.g., a PEG-based hydrogel or glass surfaces that carry thiol or olefin moieties). Synthesis is then performed via adding, for example, the components of an Ugi-reaction in a spatially defined fashion. The identity (or combination of diversity reagents) for each compound is thereby defined by its position in the microarray. Often, fluorescence is used for detection [165], but other technologies such as surfece plasmon resonance (SPR) have been used as well [166]. 

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