Bifunctional hydrogen peroxide electrode as an amperometric transducer for biosensors

This work presents a novel approach to design an amperometric transducer capable to detect hydrogen peroxide in anodic (oxidation) and cathodic (reduction) mode of operation, The basic transducer employs non-platinum 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 designing a glucose biosensor utilizing glucose oxidase (GOD) as second enzyme. A technique for preparation of the transducer electrode with the catalyst and adsorbed enzymes (bienzyme electrode) from a pressed matrix (tablet) of Teflonized carbon black is described, This technique allows manufacturing of numerous sensors from the same pressed tablet, all of which demonstrate good reproducibility of their parameters (sensitivity, linear range, lifetime). Bifunctional glucose sensors were operated in H2O2 oxidation mode at applied potentials from +0.2 to +0.6 V versus Ag/AgCl, and in H2O2 reduction mode at 0.0 V versus the same reference electrode. Linearity of the sensor response to glucose concentrations up to 25 mM in H2O2 reduction mode is reported. Electro-interference from some substances commonly present in physiological fluids was investigated in both reduction and oxidation modes. Sensors can be used for continuous glucose monitoring in vitro for at least 1 month with constant parameters of the signal output, Sensor demonstrated satisfactory performances in undiluted blood plasma in vitro. (C) 1997 Elsevier Science S.A.