Enzymatic Direct Electron Transfer at Ascorbate Oxidase-modified Gold Electrode Prepared by One-step Galvanostatic Method

A one-step enzyme immobilization by galvanostatic method at gold electrode was applied to achieve direct electron transfer (DET) of ascorbate oxidase from Acremonium sp. (ASOM). The enzyme immobilization was optimized and ASOM was successfully deposited on the gold electrode surface, typically by flowing the oxidation current of 6 mu A corresponding to oxygen evolution for 4 min, which results in a decrease in the local pH in the vicinity of the electrode surface and the precipitation of ASOM on the electrode surface due to the neutralization of its surface charge. A well-defined redox wave with a formal potential of 242 mV (vs. Ag vertical bar AgCl vertical bar KCl(sat)) was observed in 5.0 mM phosphate buffer solution (pH 7.0), confirming DET between ASOM and gold electrode surface.