A MINIATURIZED GLUCOSE BIOSENSOR BASED ON THE COIMMOBILIZATION OF GLUCOSE-OXIDASE AND FERROCENE PERCHLORATE IN NAFION AT A MICRODISK PLATINUM-ELECTRODE

A miniaturized glucose biosensor based on the coimmobilization of Fc() (ferrocene perchlorate)/GOD (glucose oxidase) in nafion film at the surface of a microdisk platinum electrode was fabricated and successfu lly used for the amperometric determination of glucose. The influences of various experimental conditions, including the relative amounts of glucose oxidase in diluted nafion aqueous solution, the concentration of ferrocene perchlorate and oxygen etc., were investigated in this p aper. Ferrocene perchlorate as a redox mediator could catalyze the oxi dation of the generated H2O2 based on the enzymatic reaction of glucos e in the presence of glucose oxidase and oxygen at a favorable lower w orking potential (ca. 0.25 V vs. SCE). Moreover, it could also oxidize the reduced flavin adenine dinucleotide (FADH(2)) of glucose oxidase directly in anaerobic environment. The response time and the detection limit under an optimal parameters were 2 min and 1 x 10(-5) M, respec tively. The interferences of ascorbic acid and uric acid could be obvi ously reduced because of the ion-selective characteristics of nafion f ilm and a favorable lower working potential. From the Michealis-Menten analysis, the apparent Michaelis constants for glucose and the maximu m limiting currents determined were 10.7 mM and 5.1 nA for the incorpo ration of Fc(+) in 1.00 mM Fc(+) solution, 7.06 mM and 5.85 nA in 2.00 mM Fc(+), respectively, Moreover, using water instead of organic solv ents for nafion dilution made this enzyme electrode exhibit a good sta bility and reproducibility for a long-term use. (C) 1997 Elsevier Scie nce S.A.