Amperometric Ascorbic Acid Biosensors Based on the Oxygen and Glassy Carbon Electrodes Modified with Ascorbate Oxidase Immobilized-silk Fibroin/polyethylene Glycol Membrane

Amperometric biosensors for the specific determination of ascorbic acid (AA) were developed by immobilizing ascorbate oxidase (ASOD) on a polyethylene glycol (PEG) modified silk fibroin (SF) membrane coupled to either the O-2 electrode or the glassy carbon electrode (GCE). Both the O-2 electrode and the GCE modified with SF/PEG/ASOD displayed their best sensor response at the same optimum conditions (0.40 mg/L of ASOD in phosphate buffer, pH 5). By comparing the responses of both AA biosensors, the GCE based biosensor showed better linearity (r(2) = 0.999 in the range of 0.5-12.0 mM) with shorter response time (26 s) compared to the O-2 electrode based biosensor (r(2) = 0.997 in the range of 0.5-5.0 mM, response time 48 s). In addition, the GCE based biosensor exhibited better selectivity and had simpler preparation steps. However, both biosensors provided approximately the same sensitivity, but the O-2 electrode based biosensor had a longer storage time (0.703 mA.mM(-1), 9 days) than the GCE based one (0.695 mA.mM(-1), 5 days). For both biosensors, there is little interference from citric acid, sodium chloride or ethanol, but some interference (2-4% error) from glucose.