An electrochemical DNA biosensor based on gold nanofilm and stable Y junction structure

Abstract

On the basis of gold nanofilm (GNF) electrode and Y junction structure of DNA, a simple and facile single-step DNA sensing protocol with improved sensitivity and lower detection limit was successfully developed. The GNF was prepared via rapid electrooxidization of the gold surface followed by the chemical reduction of the produced gold oxide layer. The capture probe DNA (c-DNA) was firstly immobilized onto GNF electrodes via Au-S bonding, for the subsequent forming of Y junction structure with target DNA (t-DNA) and reporter probe DNA (r-DNA) labeled with methylene blue (MB). Harnessing the unique properties of GNF would allow the improved contact of MB with the electrode surface and hence boost the interfacial electron communication. Experimental results of differential pulse voltammetry (DPV) showed that the peak current of the prepared biosensor was linear with the target DNA concentration from 1.0 × 10-12 to 1.0 × 10-9 mol/L and the proposed strategy could detect the target DNA down to the level of 2.4 × 10-13 mol/L. Comparing with the traditional electrochemical sensors, the present protocol enabled the generation of electrochemical signal from scratch and possessed an improved selectivity against even a single base mismatch. Besides, this DNA sensor exhibited fairly good reproducibility, stability and reusability. © 2012 Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences.