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 successfully 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 paper. Ferrocene perchlorate as a redox mediator could catalyze the oxidation of the generated H₂O₂ based on the enzymatic reaction of glucose in the presence of glucose oxidase and oxygen at a favorable lower working potential (ca. 0.25 V vs. SCE). Moreover, it could also oxidize the reduced flavin adenine dinucleotide (FADH₂) of glucose oxidase directly in anaerobic environment. The response time and the detection limit under an optimal parameters were 2 min and 1 × 10⁻⁵ M, respectively. The interferences of ascorbic acid and uric acid could be obviously reduced because of the ion-selective characteristics of nation film and a favorable lower working potential. From the Michealis-Menten analysis, the apparent Michaelis constants for glucose and the maximum limiting currents determined were 10.7 mM and 5.1 nA for the incorporation 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 solvents for nafion dilution made this enzyme electrode exhibit a good stability and reproducibility for a long-term use.