Electron Transfer Studies Between New Fad-Dependent Glucose Dehydrogenase and Different Osmium Polymers (Applications in Biosensors and Biofuel Cells)

A new extracellular flavin adenine dinucleotide (FAD)-dependent glucose dehydrogenase from Glomerella cingulata (GcGDH) was electrochemically studied as a recognition element in glucose biosensors. The redox enzyme was recombinantly produced in Pichia pastoris, homogeneously purified and its glucose oxidizing properties on spectrographic graphite electrodes were investigated. Six different Os-polymers, the redox potentials of which ranging in a broad potential window between +15 and +489 mV vs. NHE, were used to immobilize and “wire” GcGDH to the spectrographic graphite electrode’s surface. The GcGDH/Os-polymer modified electrodes were evaluated by chronoamperometry using flow injection analysis.  The current response was investigated using a step-wisely increased applied potential. It was observed that the ratio of GcGDH:Os-polymer and the overall loading of the enzyme electrode significantly affect the performance of the enzyme electrode for glucose oxidation. The best suited Os-polymer [Os(4,4¢-dimethyl-2,2¢-bipyridine)₂(PVI)Cl]⁺ had a potential of +309 mV vs. NHE and the optimum GcGDH:Os-polymer ratio was 1:2 yielding a maximum current density of 493 µAcm^-2at a 30 mM glucose concentration.

Key words: Glucose dehydrogenase, FAD, Os-polymers, glucose biosensor, chronoamperometry, oxygen reactivity.