Fabricating three-dimensional hydrogel oligonucleotide microarrays to detect single nucleotide polymorphisms

Here, a three-dimensional (3D) oligonucleotide microarray-based fluorescent assay has been developed for single nucleotide polymorphisms (SNPs) and allele frequency determination. The 3D oligonucleotide microarray is fabricated on a home-made polyacrylamide hydrogel microarray which is generated by UV light photopolymerization of tiny acrylamide monomer droplets on a PEG terminated glass slide. After activation by glutaraldehyde (GA), the polyacrylamide hydrogel is able to react with NH2-modified oligonucleotides with high efficiency to generate a high signal-to-background ratio without the conventional blocking step. We demonstrate that the assay is able to detect complimentary 25 mer oligonucleotide target (fragment of a tumor suppressor gene P53) down to 100 pM and SNP with true-to-false ratios (the ratio of fluorescence signal from perfect matched DNA strands to that from the one-base mismatched DNA strands) above 20. Taking advantage of the high specificity of the assay, allele frequency as low as 2% can be accurately determined.