Preserved enzymatic activity of glucose oxidase immobilized on an unmodified electrode

A novel glucose oxidase (GOx) electrode has been presented through immobilizing GOx on unmodified edge plane of highly oriented pyrolytic graphite (epHOPG). The GOx/epHOPG electrode showed direct electron transfer between GOx and epHOPG due to the redox process of GOx. The measured formal potential of the redox process agrees with that of the native enzyme, suggesting that the immobilized GOx retained its enzymatic activity. The estimated electron transfer rate of the epHOPG electrode immobilized GOx is greater than those for which GOx is immobilized on modified electrodes probably due to the fact that the enzyme makes direct contact to the epHOPG surface. The GOx/epHOPG electrode showed the electrochemical oxidation behavior in the presence of glucose by the immobilized GOx. Therefore, the response of the electrode to glucose confirms that the immobilized GOx retained its enzymatic activity. The properties of the electrode as a glucose sensor are presented.