Development of a Disposable Organophosphate Biosensor

A screen-printed enzyme electrode has been developed for the determination of organophosphorus pesticides based on the detection of cholinesterase inhibition by analytes. A cholinesterase enzyme is co-immobilized with choline oxidase peroxidase on the surface of a screen printed carbon electrode. The determination of cholinesterase activity is based on a sequence of enzymatic reactions: butyryl-choline hydrolysis catalyzed by cholinesterase; choline oxidation catalyzed by choline oxidase and the formation of hydrogen peroxide; detection of hydrogen peroxide via peroxidase catalyzed electron transfer. Electroreduction of hydrogen peroxide causes an electrode potential shift due to a decrease of the reaction overvoltage. The rate of electrode potential increase is proportional to the activity of cholinesterase. The electrodes allow rapid quantitative assay of cholinesterase inhibitors, such as organophosphate pesticides, with a low detection limit in sub-micromolar concentration ranges with an overall assay time of 20 minutes. The technique employs low cost disposable sensing elements. Reproducibility of the enzyme sensor technology and the shelf lifetime of the disposable biosensors are evaluated. Applicability of the assay is illustrated by detection of common of organophosphorus pesticides.