Highly sensitive impedimetric sensing of DNA hybridization based on the target DNA-induced displacement of gold nanoparticles attached to ssDNA probe

Abstract

An impedimetric DNA sensor based on the displacement of gold nanoparticles (AuNPs) by target DNA was developed for the highly sensitive detection of DNA hybridization without signal amplification. A thiol-modified probe ssDNA (PDNA) was immobilized on a gold electrode by self-assembly followed by backfill with mercaptohexanol. Subsequently, positively charged 5 nm AuNPs were attached to the immobilized PDNA by base–Au and electrostatic interaction. Attachment of AuNPs to the immobilized ssDNA probe significantly decreased the electron transfer resistance ( Ret) of the DNA sensor. After hybridization of target ssDNA to immobilized PDNA, the AuNPs were displaced by target DNA, which led to an increase in the Ret value. Based on the displacement of AuNPs by target ssDNA, the DNA sensor showed an increased Ret response to a target DNA concentration increase from 50 fM to 1 pM. The sensor surface clearly distinguished between complementary target ssDNA from single-base pair mismatches and non-complementary ssDNA.