Biosensor for organophosphorus pesticides based on the acetylcholine esterase inhibition mediated by choline oxidase bioelectrocatalysis

The method to detect the organophosphorus (OP) pesticide was developed using an acetylcholine esterase (AChE) and choline oxidase (ChOx) bienzyme system. AChE, which is inhibited by the OP pesticide, was enzymatically linked with ChOx in solution as well as on electrodes. By employing acetylcholine as the substrate for AChE, we supplied the enzyme product choline to ChOx in order to generate electrocatalyzed current. For electrochemical signaling with AChE/ChOx, ferrocene (Fc)-mediated bioelectrocatalysis through a flavin adenine dinucleotide (FAD) cofactor of ChOx was verified experimentally. An immobilization method for ChOx on a gold electrode was designed to generate amplified and controlled signal by using poly-L-lysine charge interaction and glutaraldehyde cross-linking. Using diazinon-oxon (DZN) as a detection target among the OP pesticides, we successfully conducted an electrochemical detection on the basis of AChE inhibition mediated by the ChOx bioelectrocatalysis.