BIFUNCTIONAL HYDROGEN-PEROXIDE ELECTRODE AS AN AMPEROMETRIC TRANSDUCER FOR BIOSENSORS

This work presents a novel approach to design an amperometric transduc er capable to detect hydrogen peroxide in anodic (oxidation) and catho dic (reduction) mode of operation, The basic transducer employs non-pl atinum electrocatalyst-pyrolyzed cobalt-tetramethoxy-phenylporphyrin ( CoTMPP)-for H2O2 electrooxidation, and bio-electrocatalyst-horseradish peroxidase (HRP)-for H2O2 electroreduction. The bifunctional hydrogen peroxide electrode was used as an amperometric transducer in designin g a glucose biosensor utilizing glucose oxidase (GOD) as second enzyme . A technique for preparation of the transducer electrode with the cat alyst and adsorbed enzymes (bienzyme electrode) from a pressed matrix (tablet) of Teflonized carbon black is described, This technique allow s manufacturing of numerous sensors from the same pressed tablet, all of which demonstrate good reproducibility of their parameters (sensiti vity, linear range, lifetime). Bifunctional glucose sensors were opera ted in H2O2 oxidation mode at applied potentials from +0.2 to +0.6 V v ersus Ag/AgCl, and in H2O2 reduction mode at 0.0 V versus the same ref erence electrode. Linearity of the sensor response to glucose concentr ations up to 25 mM in H2O2 reduction mode is reported. Electro-interfe rence from some substances commonly present in physiological fluids wa s investigated in both reduction and oxidation modes. Sensors can be u sed for continuous glucose monitoring in vitro for at least 1 month wi th constant parameters of the signal output, Sensor demonstrated satis factory performances in undiluted blood plasma in vitro. (C) 1997 Else vier Science S.A.