| Abstract
| - An enzyme electrode for the detection of V-type nerveagents, VX (O-ethyl-S-2-diisopropylaminoethyl methylphosphonothioate) and R-VX (O-isobutyl-S-2-diethylaminoethyl methylphosphonothioate), is proposed. Theprinciple of the new biosensor is based on the enzyme-catalyzed hydrolysis of the nerve agents and amperometricdetection of the thiol-containing hydrolysis products atcarbon nanotube-modified screen-printed electrodes.Demeton-S was used as a nerve agent mimic. 2-(Diethylamino)ethanethiol (DEAET) and 2-(dimethylamino)ethanethiol (DMAET), the thiol-containing hydrolysis product and hydrolysis product mimic of R-VX and VX,respectively, were monitored by exploiting the electrocatalytic activity of carbon nanotubes (CNT). As low as 2μM DMAET and 0.8 μM DEAET were detected selectivelyat a low applied potential of 0.5 V vs Ag/AgCl at a CNT-modified mediator-free amperometric electrode. Further,the large surface area and the hydrophobicity of CNT wasused to immobilize organophosphorus hydrolase mutantwith improved catalytic activity for the hydrolysis of theP−S bond of phosphothiolester neurotoxins including VXand R-VX nerve gases to develop a novel, mediator-free,membrane-free biosensor for V-type nerve agents. Theapplicability of the biosensor was demonstrated for direct,rapid, and selective detection of V-type nerve agents'mimic demeton-S. The selectivity of the sensor againstinterferences and application to spiked lake water sampleswas demonstrated.
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