Covalent immobilization of glucose oxidase on conducting ultrananocrystalline diamond thin films

We demonstrate in this report the covalent immobilization of redox enzymes onto electrically conductive ultrananocrystalline diamond (UNCD) thin films. Glucose oxidase was attached to the UNCD surface via the tethered aminophenyl functional groups which were previously grafted to UNCD surface by electrochemical reduction of aryl diazonium salt. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) observations confirmed the surface functionalization. The tethered glucose oxidase maintains its biocatalytic activity, and the electrical communication between the enzyme active sites and the UNCD surface was established using molecular oxygen as the electron mediator. Our results suggest that conductive diamond thin films, owing to their excellent mechanical, electrical and electrochemical properties, could serve as a robust platform for a new class of bioinorganic interfaces and electrochemical biosensors.