Amperometric Biosensors Based on Choline Oxidase Entrapped in Polyacrylamide Microgels

Abstract

Abstract A choline amperometric biosensor has been designed using as biological component choline oxidase (ChOx) entrapped in polyacrylamide microgels. The working electrode was prepared by holding the enzyme loaded microgels on a platinum electrode by a dialysis membrane. It was found that the optimum microgel cross‐linking required to retain ChOx and to allow the diffusion of choline was 7.0%. The response of the biosensor was optimized in relation to pH, temperature and working potential and the following optimal values were obtained: pH 9.0, temperature range between 20 and 30 °C, and potential +0.6 V. Under optimal conditions the sensitivity for choline was 17.45 mA M −1 cm −2 , the detection limit 8 μM, and the response linear range from 2×10 −5 M to 2×10 −4 M. This biosensor has been also used as a nicotine detector due to the inhibition of the catalytic activity of choline oxidase by this compound. Moreover, the simultaneous entrapment of a second enzyme, acetylcholinesterase (AChE), in the microgels makes the biosensor sensible to acetylcholine.