RAPID DETECTION OF ANTICHOLINESTERASE INSECTICIDES BY A REUSABLE LIGHT ADDRESSABLE POTENTIOMETRIC BIOSENSOR

A light addressable potentiometric sensor (LAPS) was used to detect organophosphate and carbamate anticholinesterases (anti-ChEs), using eel acetylcholinesterase (AChE) as the biological sensing element. Biotinylated AChE was preincubated with inhibitor or buffer alone and then captured on biotinylated nitrocellulose membrane via streptavidin cross-linking, or AChE was preimmobilized on the capture membrane and then a sample containing the anti-ChE was filtered through the capture membrane. Hydrolysis of acetylcholine (ACh) by the captured AChE resulted in a strong potentiometric signal, and the immobilized AChE retained its affinity for ACh and anti-ChEs. IC50 values for inhibition of captured AChE obtained by the LAPS agreed with those obtained by a spectrophotometric method or a fiber optic evanescent fluorosensor. Paraoxon and bendiocarb were detected at 10 nM, while higher concentrations were required for monocrotophos, dicrotophos, dichlorvos, phosdrin, diazinon, tetraethyl pyrophosphate, aldicarb, and methomyl. Important features of the LAPS for detection of anti-ChEs are speed (eight samples assayed simultaneously in minutes), precision, and reusability.