A reusable and label-free supersandwich biosensor for sensitive DNA detection by immobilizing target-triggered DNA concatamers on ternary self-assembled monolayer

Abstract

A reusable and label-free supersandwich biosensor was constructed for sensitive DNA detection by immobilizing target-triggered DNA concatamers with redox-active intercalators on ternary self-assembled monolayer (TSAM). Interestingly, the target DNA (T-DNA) could hybridize with the inert dumbbell-shaped DNA (D-DNA) to form a duplex DNA containing two sticky termini. The duplex DNA was then hybridized with the capture DNA (C-DNA) and the DNA concatamer reaction proceeded. The ternary self-assembly method was chosen to obtain the low-density C-DNA without reciprocal winding on the gold electrode for high-efficient concatamers hybridization. Hexaammineruthenium chloride was herein used as an electrochemical probe and could intercalate into the groove of double-helix DNA via electrostatic effect. The resultant supersandwich biosensor showed a high sensitivity for the T-DNA detection and a linear dependence between the reduction peak currents and logarithm of T-DNA concentrations in the range of 100.0 fM–10.0nM with a relatively low detection limit of 30.0 fM. Moreover, the proposed biosensor exhibited favorable specificity and regenerability, and provided a new alternative to detect various target analytes by changing the sequence of capture probe and dumbbell probes, holding great potential for early diagnosis in gene-related diseases.