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Carbon nanotube-based electrochemical sensor for cholinesterase enzyme activity: an organophosphorus insecticide and nerve agent exposure monitor.

Wang-J; Liu-G; Timchalk-C; Lin-Y
Toxicologist 2008 Mar; 102(1):360
Simple, rapid and sensitive analytical sensors are needed to evaluate exposures to organophosphorus insecticides and nerve agents utilizing readily obtainable biological fluids, like saliva. An electrochemical sensor coupled with a micro-flow injection system was developed to characterize cholinesterase (ChE) enzyme activity. The sensor is based on a carbon nanotube (CNT)-modified screen-printed carbon electrode (SPE) integrated into a flow cell. The electrocatalytic activity of the carbon nanotubes, enable the sensor to detect electroactive species that are produced from enzymatic reactions with high sensitivity. The electrochemical properties of ChE enzymatic products were studied using the sensor, and the operation parameters such as the applied potential and substrate concentration were optimized. ChE activity was further investigated using the CNT-based sensor with purified human acetylcholinesterase (AChE) and in vitro with saliva obtained from naive rats. For purified AChE the calibration curve was linear over a range of concentrations (5 pM to 0.5 nM) and the detection limit was estimated to be ~2 pM. The dynamics of salivary ChE activity was also studied in vitro. Paraoxon (0.7 nM and 7 nM) was mixed with 10-fold diluted saliva (1:1 v/v) and incubated for different time periods (5 to 120 min) then 100 microL of the mixed solution was reacted with an equal volume of 5 mM acetylthiocholine (~10 min) and sequentially assayed with the sensor. A concentration-dependent inhibition of salivary ChE activity was observed. At 0.7 nM paraoxon, the sensor response indicated ~80% enzyme inhibition within 0.5 h; whereas, at 7 nM 100% inhibition was achieved. Future studies will evaluate the sensor performance following in vivo exposure of rats to ChE inhibiting pesticides. This new CNT-based electrochemical sensor represents a potential next generation sensor for noninvasive biomonitoring of exposure to OP insecticides and chemical nerve agents.
Agricultural-chemicals; Insecticides; Organo-phosphorus-compounds; Organo-phosphorus-pesticides; Electrochemical-analysis; Electrochemical-reactions; Electrochemistry; Biological-effects; Laboratory-animals; Pesticide-residues; Pesticides-and-agricultural-chemicals; Chemical-agent-detectors; Chemical-analysis; Chemical-synthesis; Monitors; Nanotechnology
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Agriculture, Forestry and Fishing
Source Name
The Toxicologist. Society of Toxicology 47th Annual Meeting and ToxExpo, March 16-20, 2008, Seattle, Washington
Performing Organization
Battelle Pacific Northwest Laboratories