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Development of A Handheld Pest-pen Device For The Rapid Detection of Organophosphate Insecticides On Food and Clothing

Rosenberg, Yvonne J
Plantvax, Inc.
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ABSTRACTThe neurotoxicity of OP pesticides in humans may result from dermal or inhalation exposure onclothing or machinery or orally from the residue on food. In the latter context, the healthconsequences associated with the use of organophosphate (OP) pesticides, especially in children,could be reduced by monitoring produce and eliminating the consumption of OP-contaminated food.PlantVax currently employs the Nicotiana benthamiana plant expression system to produce highlevels of recombinant human acetylcholinesterase (rHuAChE) which is used in devices eg the FLIRCADpen, for the detection of trace amounts of organophosphate (OP) nerve agents for militarypurposes. In this proposal, PlantVax aims to develop a simplified, hand-held inexpensive PEST-pento rapidly detect phosphorothionate insecticides on food, clothing and machinery. While the newdevice will utilize the same esterase-based embedded chemistry as the CADpen with a yellow tored color as a read-out, important features need to be altered to increase the rate of color changeefficacy of the new device. Firstly, the inhibition constants (ki) obtained for carboxylases (CES) arehigher for insecticides than HuAChE and will initially be incorporated into the pen sponge. Secondlysince phosphorothionate insecticides are inactive and need to be metabolically converted byoxidative desulfuration into the active oxon form by cytochrome P450 in the liver for theirinsecticidal action, the PEST-pen may need to integrate features of both thion oxidation to an oxonas well as CES/AChE inhibition into a single device. The innovation in this proposal will be theidentification of novel indicator molecules with high inhibition rates for incorporation into the sponge.These include (i) the wildtype or G137D mutant form of the carboxylesterase enzyme from theAustralian blow fly Lucilia cuprina (Lc?E7) which exhibits high kinetic parameters for thion forms or(ii) mutant AChE enzyme with increased rates of inhibition by oxon embedded together with a P450,in the presence of a cytochrome c reductase (NADPH), to expedite conversion to the oxonforms.Based on the design of the successful CADpen, several PEST-pen prototypes with differentindicator molecules will be produced and tested within a year.
Funding Source
Nat'l. Inst. of Environmental Health Sciences
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Policy and Planning