Add time:07/24/2019         Source:sciencedirect.com

In this work, a label-free electrochemical biosensor is fabricated for the detection of nereistoxin (NRT)-related insecticides based on NRT binding-triggered conformational switching of DNAzyme and micropipette tip-based miniaturized homogeneous electrochemical device. NRT-related insecticides are first converted into NRT with two sulfhydryl groups in a pretreatment step. Then, the thymine-Hg2+-thymine (T-Hg2+-T) mismatch is used to induce the programmed assembly of DNAzyme subunits into functional catalytic structures, thereby activating the Mg2+-DNAzyme and the subsequent hemin/G-quadruplex DNAzyme, respectively. The electrochemical signals generated by the catalytic activity of hemin/G-quadruplex DNAzyme are recorded using a miniaturized electrochemical device. After introduction of the converted NRT, the catalytic functions of Mg2+-DNAzyme are switched-off by uptaking Hg2+ from Mg2+-DNAzyme to disband its catalytic structure, and block the electrochemical signal generation pathway. With such design, a highly sensitive “signal-off” strategy is proposed for bensultap (BST) detection, with a 6.9 ng/L detection limit and 0.01–2000 μg/L linear range. Our strategy also demonstrates the applicability of BST detection in agricultural products.

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