Exonuclease III-assisted positive feedback signal amplification strategy for ultrasensitive electrochemical detection of nucleic acids

Abstract

Diffusion-mediated homogeneous electrochemical assay has attracted substantial attention owing to its simplicity, rapid response, and high recognition efficiency, however, lack of inherent connection between signal reporter and electrode surface restricts the improvement of detection sensitivity and further limits its potential applications. Herein, a facile electrochemical strategy is proposed through integrating the advantages of traditional heterogeneous assay and homogenous assay. In this strategy, a small amount of target DNA can trigger the release of assist DNA from the electrode surface. Then, the assist DNA can induce the homogeneous amplification reaction, which in turn promotes the amplification on the electrode surface by generating numerous target DNA analogues, thereby realizing positive feedback signal amplification. As a result, ultrasensitive electrochemical detection of nucleic acids was achieved in the dynamic range from 5 aM to 5 fM with a detection limit down to 1.2 aM. There is about 2.5 orders of magnitude improvement in sensitivity compared with the control strategy without homogeneous amplification. Moreover, the proposed strategy was demonstrated with high selectivity, reproducibility, and capability of detecting nucleic acids in serum samples, displaying its promising potential in the development of ultrasensitive electrochemical biosensing platform for disease diagnosis applications.