Electrochemical DNA probe for Hg2+ detection based on a triple-helix DNA and Multistage Signal Amplification Strategy

Abstract

In this work, an ultrasensitive electrochemical sensor was developed for detection of Hg2+. Gold nanoparticles decorated bovine serum albumin reduction of graphene oxide (AuNP-BSA-rGO) were used as subsurface material for the immobilization of triple-helix DNA. The triple-helix DNA containing a thiol labelled single-stranded DNA (sDNA) and a thymine-rich DNA (T-rich DNA), which could be unwinded in the present of Hg2+ to form more stable thymine–Hg2+–thymine (T–Hg2+–T) complex. T–Hg2+–T complex was then removed and the sDNA was left on the electrode. At this time, gold nanoparticle carrying thiol labelled cytosine-rich complementary DNA (cDNA-AuNP) could bind with the free sDNA. Meanwhile, the other free cDNA on AuNP could bind with each other in the present of Ag+ to form the stable cytosine–Ag+–cytosine (C–Ag+–C) complex and circle amplification. Plenty of C–Ag+–C could form silver nanoclusters by electrochemical reduction and the striping signal of Ag could be measured for purpose of the final electrochemical detection of Hg2+. This sensor could detect Hg2+ over a wide concentration range from 0.1 to 130nM with a detection limit of 0.03nM.