A study on electrodeposition of glucose oxidase from low conductivity solutions

By Ammam, Malika & Fransaer, Jan
Published in Electrochimica Acta NULL 2010

Abstract

In this paper, we have investigated the deposition of glucose oxidase from ultrapure water at relatively high applied potential of 4 V vs. Ag/AgCl, as a new deposition technique. Compared to GOx deposited from phosphate buffer, the enzyme electrode prepared from ultrapure water displayed a nearly 10 times higher amperometric response. EQCM measurements showed that the mass and thickness of the deposited enzyme layer from water is nearly 18 times higher than the enzyme deposited from buffer. This difference is also reflected in the impedance spectroscopy and AFM measurements. The electron transfer resistance is higher for the GOx film deposited from water than the GOx deposited from buffer and, AFM displayed a thick and rough film for the GOx deposited from water, while underlying and a smooth morphology were observed for GOx film deposited from buffer. The zeta potential of GOx in water is nearly 25 times higher than the zeta potential measured in buffer. These observations suggest that the GOx deposited from water is subject to both the electrophoretic migration of the enzyme from the bulk to the interface and precipitation at the electrode interface as a consequent of a local decrease in pH. By contrast, deposition of GOx from buffer is only due to a change in pH. The effects of deposition time, enzyme concentration and applied potential on the enzyme deposition from water were explored. The current response of the enzyme electrode as well as the uptake in mass onto the electrode measured by EQCM increase quasi-linearly with deposition time, enzyme concentration and applied potential up to 4 V.

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