Fluorescence Quenching-Based Evaluation of Glucose Oxidase Composite with Conducting Polymer, Polypyrrole

Glucose oxidase (GOx) composites with conducting polymers (e.g., polypyrrole (Ppy)) are excellent nanobiomaterials suitable for the design of bioelectronic devices such as biosensors and biofuel cells. Here, we address the spectroscopic properties of GOx, flavin adenine dinucleotide (FAD), and composites of these compounds with polypyrrole (Ppy). The exploration of native GOx and FAD solutions confirmed that about 5% of FAD dissociated from GOx during the period of solution preparation, and this fraction remained constant for 1 month. It has been found that the Ppy, which formed composites with FAD and GOx, facilitated the removal of FAD molecules from GOx and twice reduced the fluorescence decay rate. Differences in the FAD and Ppy average fluorescence relaxation times showed that the FAD composite with Ppy and Ppy effectively quenched the FAD fluorescence and FAD could not freely unfold. The intramolecular electron transfer took place between adenine and isoalloxazine moieties over the first 5 ps after the excitation. The findings are very useful in the selection and adaptation of enzyme immobilization strategies, which are applied in the development of biosensors and biofuel cells.