Electrocatalytical oxidation of glucose on graphite using covalently immobilized glucose oxidase and 1,6-dithia- and 1,6-dioxapyrenes as mediators

Electrocatalytical oxidation of glucose on graphite using new mediators (1,6‐dithiapyrenes (DTPs) and 1,6‐dioxapyrenes) was performed. The electrocatalysis of glucose oxidase (GO) was based on the dithia(dioxa)pyrene cation‐radicals reaction with reduced GO. The rate of reduced GO oxidation by the cation‐radical of dithiapyrene was 4.8 × 10⁴ M⁻¹ s⁻¹ at 25°C (pH 7.0). For enzyme electrode preparation, the GO was covalently immobilized by carbodiimide, and the mediator was adsorbed on a graphite electrode. The dithia(dioxa)pyrenes mediated glucose oxidation proceeds at potentials higher than 0.1 V (versus standard calomel electrode (SCE)). Of the investigated substituted dithia(dioxa)pyrenes, the largest electrocatalytical current was observed with electrodes comprising of DTP. Linear calibration graphs of these electrodes were obtained up to 12 mM of glucose, the maximal electrode activity was in the range of pH 6.5 to 8.0, and the temperature coefficient was 5.6%/°C. The investigated electrocatalytical systems can be used for construction of disposable senses for glucose determination in physiological solutions.