An electronic sensor array for label-free detection of single-nucleotide polymorphisms

Abstract

A highly sensitive and selective electronic sensor array for label-free detection of single-nucleotide polymorphisms (SNPs) is described in this work. Its sensing mechanism relies on building target DNA-templated silver nanowires (conductive paths) across a nanogap. Following hybridization with a SNP target, a cocktail of nucleases is applied to the nanogap sensor array. Free capture probes (CPs) and imperfectly hybridized CPs are digested while the perfectly hybridized CPs are covalently joined together over the nanogap at the mutation site. Detection of SNPs down to 0.10fM is realized by measuring the conductance of the nanogap after a simple DNA metallization step. The engagement of the nucleases grants the nanogap sensor excellent ability to discriminate against mismatched sequences and allows hybridization to be carried out at very low stringency (room temperature), enabling a highly selective approach for SNP genotyping. And hybridization at low stringency ensures that all targets will be preferably hybridized at equilibrium. A selectivity factor of 3000 is observed when a mixture of a wild-type and a mutated gene is analyzed by the sensor array. Attempts are made in applying the sensor array to the detection of SNPs in DNA samples extracted from tissues and cultured cells.