Covalently immobilized choline oxidase and cholinesterases on a methacrylate copolymer for disposable membrane biosensors

Bienzymatic sensors for the determination of esters of choline were prepare d by covalent co-immobilization of cholinesterases and choline oxidase on p olymer membranes, obtained by radiation-induced copolymerization of 2-hydro xyethyl methacrylate and glycidyl methacrylate at low temperature. Optimiza tion of the covalent attachment of choline oxidase and acetyl- or butyrylch olinesterase to copolymer was explored. The enzyme-modified polymers were a pplied on platinum electrodes to form amperometric sensors, based on the el ectrochemical detection of enzymatically developed hydrogen peroxide. Acety l-, acetylthio-, butyryl-, and butyrylthiocholine contents in standard solu tions were measured, and linear calibration curves were determined. Tempera ture and pH effects on the electrochemical response are described.