A pair of well-defined and reversible redox peaks was observed for the direct electron transfer (DET) reaction of an immobilized glucose oxidase (GOx) on the surface of a nano-porous glassy carbon electrode at the formal potential (E degrees') of -0.439 V versus Ag/AgCl/saturated KCl. The electron transfer rate constant (k(s)) was calculated to be 5.27 s(-1). The dependence of E degrees' on pH indicated that the direct electron transfer of the GOx was a two-electron transfer process, coupled with two-proton transfer. The results clearly demonstrate that the nano-porous glassy carbon electrode is a cost-effective and ready-to-use scaffold for the fabrication of a glucose biosensor. (C) 2011 Elsevier Ltd. All rights reserved.