RESUMO
Organophosphate (OP) pesticides remain a worldwide health concern due to their acute or chronic poisoning and widespread use in agriculture around the world. There is a need for robust and field-deployable tools for onsite detection of OP pesticides in food and water. Herein, we present an integrated smartphone/resistive biosensor for simple, rapid, reagentless, and sensitive monitoring of OP pesticides in food and environmental water. The biosensor leverages the hydrolytic activity of acetylcholinesterase (AChE) to its substrate, acetylcholine (ACh), and unique transport properties of polyaniline nanofibers (PAnNFs) of chitosan/AChE/PAnNF/carbon nanotube (CNT) nanocomposite film on a gold interdigitated electrode. The principle of the sensor relies on OP inhibiting AChE, thus, reducing the rate of ACh hydrolysis and consequently decreasing the rate of protons doping the PAnNFs. Such resulted decrease in conductance of PAnNF can be used to quantify OP pesticides in a sample. A mobile app for the biosensor was developed for analyzing measurement data and displaying and sharing testing results. Under optimal conditions, the biosensor demonstrated a wide linear range (1 ppt-100 ppb) with a low detection limit (0.304 ppt) and high reproducibility (RSD <5%) for Paraoxon-Methyl (PM), a model analyte. Furthermore, the biosensor was successfully applied for analyzing PM spiked food/water samples with an average recovery rate of 98.3% and provided comparable results with liquid chromatography-mass spectrometry. As such, the nanosensing platform provides a promising tool for onsite rapid and sensitive detection of OP pesticides in food and environmental water.