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Abstract
Organophosphorus (OP) compounds are neurotoxins that are among the most widely used pesticides in agriculture in the United States. In this application, a new integrated point-of-care smartphone/resistive nanosensor device is developed for onsite rapid and sensitive detection of exposure to OP pesticides from a drop of finger-stick blood among a sample of farmworkers. The nanosensor leverages the transport properties of a multiwalled carbon nanotube/polyaniline nanofiber (MWCNT/PAnNF) nanocomposite film on a gold interdigitated electrode and acetylcholinesterase/butyrylcholinesterase (AChE/BChE) hydrolysis of their respective substrates generating protons doping PAnNFs, thereby increasing the conductance of the film. As such, a conductance change can be used to quantify cholinesterase activity, enabling assessment of acute/chronic OP poisoning. Additionally, a mobile app was developed for the nanosensor to process, display, track, and share results. Under optimal conditions, the nanosensor demonstrated exceptional sensitivity with the detection limits of 0.11 U/mL for AChE and 0.093 U/mL for BChE, physiologically relevant dynamic ranges of 2.0–18.0 U/mL for AChE and 0.5–5.0 U/mL for BChE in whole blood, and high reproducibility with the relative standard variation of <4%. The nanosensor was further validated with widely used radiometric and Ellman’s methods, utilizing both in vitro pesticide-spiked blood samples and blood samples from 22 farmworkers. The results between this nanosensor and those two methods demonstrated a strong agreement. This platform provides a new avenue for the simple, rapid, and sensitive biomonitoring of OP pesticide exposure.