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

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 130 nM with a detection limit of 0.03 nM. (C) 2016 Elsevier B.V. All rights reserved.