title: V-type nerve agent detection using a carbon nanotube-based amperometric enzyme electrode.
abstract: An enzyme electrode for the detection of V-type nerve agents, VX (O-ethyl-S-2-diisopropylaminoethyl methylphosphonothioate) and R-VX (O-isobutyl-S-2-diethylaminoethyl methylphosphonothioate), is proposed. The principle of the new biosensor is based on the enzyme-catalyzed hydrolysis of the nerve agents and amperometric detection of the thiol-containing hydrolysis products at carbon 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 2 microM DMAET and 0.8 microM DEAET were detected selectively at 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 was used to immobilize organophosphorus hydrolase mutant with improved catalytic activity for the hydrolysis of the P-S bond of phosphothiolester neurotoxins including VX and R-VX nerve gases to develop a novel, mediator-free, membrane-free biosensor for V-type nerve agents. The applicability of the biosensor was demonstrated for direct, rapid, and selective detection of V-type nerve agents' mimic demeton-S. The selectivity of the sensor against interferences and application to spiked lake water samples was demonstrated.
authors.affiliation: Department of Chemical and Environmental Engineering, University of California, Riverside, California 92521, USA.
authors.forename: Kanchan A
authors.initials: KA
authors.lastname: Joshi
authors.forename: Marek
authors.initials: M
authors.lastname: Prouza
authors.forename: Maxwell
authors.initials: M
authors.lastname: Kum
authors.forename: Joseph
authors.initials: J
authors.lastname: Wang
authors.forename: Jason
authors.initials: J
authors.lastname: Tang
authors.forename: Robert
authors.initials: R
authors.lastname: Haddon
authors.forename: Wilfred
authors.initials: W
authors.lastname: Chen
authors.forename: Ashok
authors.initials: A
authors.lastname: Mulchandani
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D002619:Chemical Warfare Agents / Q000032:analysis*; D004563:Electrochemistry; D036103:Nanotechnology; D037742:Nanotubes, Carbon; D009498:Neurotoxins / Q000032:analysis*; D009946:Organothiophosphorus Compounds / Q000032:analysis*; D013438:Sulfhydryl Compounds
chemical_list: D002619:Chemical Warfare Agents; D037742:Nanotubes, Carbon; D009498:Neurotoxins; D009946:Organothiophosphorus Compounds; D013438:Sulfhydryl Compounds; C009680:VX-agent