A Screen‐Printed, Amperometric, Biosensor Array for the Detection of Organophosphate Pesticides Based on Inhibition of Wild Type, and Mutant Acetylcholinesterases, from Drosophila melanogaster

Abstract

Screen‐printed carbon electrodes (SPCEs) modified with cobalt phthalocyanine (CoPC) have been used as base transducers in the construction of amperometric pesticide biosensors. Six individual biosensors were fabricated by depositing wildtype (WT) acetylcholinesterase (AChE) from Drosophila melanogaster or one of five mutant forms (B02, B03, B04, B421, and B65) of this enzyme, onto the surfaces of CoPC‐SPCEs; these constituted the amperometric biosensor array. The enzyme converts acetylthiocholine into its electroactive product thiocholine, which is detected at only 0 V vs. Ag/AgCl at the CoPC‐SPCEs. The measurement step is performed using chronoamperometry. In the presence of an organophosphate (OP) pesticide, the enzyme is inhibited, which leads to a decrease in thiocholine production and a corresponding decrease in anodic current. This decrease is proportional to the logarithm of the pesticide concentration. Calibration studies were performed with the biosensor array using five OPs of interest to the food industry, namely omethoate, malaoxon, dichlorvos, chlorpyrifos‐methyl‐oxon, and pirimiphos‐methyl‐oxon. It was found that different inhibition patterns occurred for the five OPs indicating the possibility of identifying and quantifying these compounds in food samples. It should be added that there was no detrimental affect on the biosensor response from wheat or apple extracts.