Target-Induced DNA Mismatch for One-Spot Simultaneous Electrochemical Detection of Multiple Heavy Metals Based on the Amplification of DNA Concatemers

Abstract

Here, we develop a sensitive and selective method for simultaneous detection of Ag+ and Hg2+ by target-induced conformational switch and DNA concatemers amplification protocol. Two dsDNA strands, one is thiol labeled C-rich oligonucleotide (C1) and its partially complementary DNA (P1), the other is thiol labeled T-rich oligonucleotide (C2) and its partially complementary DNA (P2), were firstly coimmobilized on electrode. When four auxiliary DNA strands, anthraquinone-2-carboxylic acid (AQ) labeled LS1 and LS2, thionine (Thi) labeled LS3 and LS4, were introduced, extended dsDNA polymers with lots of AQ moieties and Thi moieties could be formed on electrode, which were employed P1 and P2 as primers for concatemer reaction. In the presence of Ag+ and Hg2+, C1 and C2 on electrode via the insertion approach can fold into hairpin structures, resulting in the release of redox-tagged DNA concatemers from electrode with a substantially decreased redox current for quantitatively detecting the targets. As a result, the proposed aptasensor showed a good linear relationship between reduction peak currents and analyte concentrations in the ranges from 0.01 nM to 5 μM with a detection limit of 2 pM for Ag+, and 0.5 nM to 50 μM with a detection limit of 7.5 pM for Hg2+, respectively.