Direct electron transfer of glucose oxidase on carbon nanotubes

Abstract

In this report, exploitation of the unique properties of single-walled carbonnanotubes (SWNT) leads to the achievement of direct electron transfer with theredox active centres of adsorbed oxidoreductase enzymes. Flavin adeninedinucleotide (FAD), the redox active prosthetic group of flavoenzymes thatcatalyses important biological redox reactions and the flavoenzyme glucoseoxidase (GOx), were both found to spontaneously adsorb onto carbon nanotubebundles. Both FAD and GOx were found to spontaneously adsorb tounannealed carbon nanotubes that were cast onto glassy carbon electrodesand to display quasi-reversible one-electron transfer. Similarly, GOx wasfound to spontaneously adsorb to annealed, single-walled carbon nanotubepaper and to display quasi-reversible one-electron transfer. In particular,GOx immobilized in this way was shown, in the presence of glucose, tomaintain its substrate-specific enzyme activity. It is believed that thetubular fibrils become positioned within tunnelling distance of the cofactorswith little consequence to denaturation. The combination of SWNT withredox active enzymes would appear to offer an excellent and convenientplatform for a fundamental understanding of biological redox reactions aswell as the development of reagentless biosensors and nanobiosensors.