Development of a cellobiose dehydrogenase modified electrode for amperometric detection of diphenols

A new amperometric biosensor based on cellobiose dehydrogenase (CDH) was created for the detection of ortho- and para-diphenolic compounds. The developed electrode efficiently discriminates between diphenolic and monophenolic compounds. The analyte, a diphenolic compound, is oxidised on the surface of a graphite electrode at an applied potential of +300 mV vs. Ag/AgCl. The diphenol is then regenerated by the adsorbed CDH in the presence of cellobiose, thus allowing an amplified response signal. Different parameters of the CDH-electrode system were optimised, e.g., applied potential, immobilisation time, flow rate, substrate concentration and storage conditions. Using the optimised parameters the sensitivity and detection limits for various diphenolic compounds were evaluated, resulting in detection limits below 5 nM for most of the compounds tested. The highest sensitivity recorded was obtained for dopamine, 3.6 A l mol(-1) cm(-2). The operational stability of the electrodes was high: during 2 h of continuous operation only a 1-2% decrease in response signal was observed.