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 Hg 2+ by target-induced conformational switch and DNA concatemers amplification protocol. Two dsDNA strands, one is thiol labeled C-rich oligonucleotide (C 1 ) and its partially complementary DNA (P 1 ), the other is thiol labeled T-rich oligonucleotide (C 2 ) and its partially complementary DNA (P 2 ), were firstly coimmobilized on electrode. When four auxiliary DNA strands, anthraquinone-2-carboxylic acid (AQ) labeled LS 1 and LS 2 , thionine (Thi) labeled LS 3 and LS 4 , 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 Hg 2+ , C 1 and C 2 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 Hg 2+ , respectively.

Advances in Design Strategies of Multiplex Electrochemical Aptasensors

“…The selected redox compound should also show high stability and the ability to bind to nanoparticles or to form conjugates with the applicable receptor molecule without affecting its recognition functionality [ 66 , 71 ]. From among the aptasensors proposed for simultaneous multiple analytes detection, two types of sensors have most often been considered: Structure-switching sensors [ 72 ], in which the redox-tag labelled aptamer alters the conformation upon binding a target molecule, resulting in changes in the rate of electron transfer between the redox tag and electrode surface [ 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 ], and Sensors based on bioconjugates containing nanomaterials, such as gold nanoparticles (AuNPs), gold nanorods (AuNRs), or nano zirconium-metal organic framework (NMOF), modified further with aptamer and redox tag molecules [ 70 , 84 , 85 , 86 ]. …”

“…Structure-switching sensors [ 72 ], in which the redox-tag labelled aptamer alters the conformation upon binding a target molecule, resulting in changes in the rate of electron transfer between the redox tag and electrode surface [ 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 ], and…”

Hg2+ Electrochemical Biosensor Based on Target Triggered Exonuclease III-Assisted Dual Cycle Amplification and Tetrahedron DNA Nanostructures as Signal Molecule Carrier

“…[9][10][11] Recently, many researches have demonstrated that thymine-thymine (T-T) mismatches base pairs can capture Hg 2+ through N-Hg covalent bonding to form stable T-Hg 2+ -T structures, [12][13][14][15] which provided great opportunities for selective Hg 2+ detection. [16][17][18][19] However, some of them suffered from low sensitivity, complicated experimental procedures and increased costs. 18,19 Thus, it is urgently needed to develop a highly sensitive and inexpensive testing system for Hg 2+ monitoring.…”

“…[16][17][18][19] However, some of them suffered from low sensitivity, complicated experimental procedures and increased costs. 18,19 Thus, it is urgently needed to develop a highly sensitive and inexpensive testing system for Hg 2+ monitoring. Recently, the enzyme-aided target recycling strategy has been used to develop sensitive and selective detection of Hg 2+ in which cleavage activity of polymerase and nicking endonuclease on DNA duplexes with T-Hg 2+ -T base pairs was inactivated to release for Hg 2+ and initiated a new cycle to amplify response signal.…”