Electrochemical Functionalization as a Promising Avenue for Glucose Oxidase Immobilization at Carbon Nanotubes: Enhanced Direct Electron Transfer Process

This work demonstrates an approach for building bioelectrocatalytic interfaces by electrochemically functionalizing carbon nanotubes surface to create a conductive matrix for immobilization of enzymes. Such a strategy not only is simple but presents an opportunity to intimately interface an enzyme and manifests direct electron transfer features. Electrochemically functionalized carbon nanotubes (CNTEF)-glucose oxidase (GOx) electrodes are evaluated electrochemically and characterized by means of FESEM and X-ray photoelectron spectroscopy (XPS). The immobilization of GOx on the CNTs surface was confirmed with XPS analysis. Square wave voltammetry of the CNTEF-GOx in argon saturated PBS solution (pH 7.2) displayed a net current peak at a potential close to that of the FAD/FADH2 cofactor of immobilized GOx. In the presence of glucose, the immobilized GOx demonstrated its ability to simultaneously undergo DET with the electrode and retains biocatalytic activity up to 10 mM of glucose concentration. The proposed electrochemical functionalization method could be without doubt extended to immobilize and evaluate the direct electron transfer of other redox enzymes or proteins on carbon nanostructures.