Rapid and sensitive visual detection of residual pesticides in food using acetylcholinesterase-based disposable membrane chips

The neurotoxic property of organophosphate pesticides due to the inhibition of acetylcholinesterase (AChE) was utilized to develop disposable detection chips for easy and fast detection of the pesticides. An enzymatic assay involving acetylcholinesterase (AChE) was developed using a stable substrate specific to the enzymatic reaction product, thiocholine. The generated thiocholine reacted with 5,5′-dithiobis-2-nitrobenzoic acid (DTNB) to produce 5′-mercapto-2′-nitrobenzoic acid, which was measured at 410 nm. Optimum pH, buffer types and concentrations, substrate concentrations and optimum conditions of the color reaction were investigated. The substrate specificity, test interferences were evaluated. Our simple detection system does not require any expensive instruments. Diazinon-oxon (DZN-oxon) could be detected by a visual color change from white to yellow on the surface of the chip. The total amount of time required for the detection of residual DZN-oxon in apple and orange juices was about an hour. This method provides excellent specificity, reproducibility, a wide measurement range and minimal interference from endogenous substances in juice matrices. Since the reagents are stable after preparation, our method would be useful for routine pesticide screening by non-professional end-users.