Single nucleotide polymorphism analysis by chip-based hybridization and direct current electrical detection of gold-labeled DNA.

Single nucleotide polymorphism (SNP) analysis at the point of care requires a low cost detection technology that is capable of miniaturization, multiplexing, and high sensitivity. Direct current electrical detection (DCED) of DNA following nanoparticle labeling and silver enhancement is a promising candidate technology for point-of-care diagnostics. In this work we present, for the first time, SNP analysis in PCR products from patient samples using DCED, taking this platform technology a step closer to practical application. We developed a silane functionalized polymer for coating of biochip surfaces. This polymeric coating is stable under harsh conditions and has exceptionally high binding capacity. Allele-specific oligonucleotide probes were immobilized on chips coated with this polymer. Biotinylated PCR products of the human cholesteryl ester transfer protein gene from different patients were hybridized to the chips, labeled with gold nanoparticles, and autometallographically enhanced. The chips were scanned for DC electrical resistance by applying movable electrodes to the surface. Eighteen of nineteen patient samples were assigned the correct genotype. Our results demonstrate that SNP analysis of patient samples is feasible with DCED.