(Invited) Glucose Sensor Prepared By the Immobilization of Glucose Oxidase Together with Nanocarbons and Prussian Blue Using Electrodeposition Method

Abstract

A variety of approaches have been explored in the immobilization of enzyme onto the electrodes. Electrochemical deposition and electropolymerization procedure are interesting, since it allows localization of enzymes onto extremely small electrode surfaces, and permits the formation of multilayer structures. The purpose of these strategies are to immobilize enzyme in a highly active state and, at the same time, provide a membrane preferentially permeable to hydrogen peroxide over endogenous electroactive species, such as uric and ascorbic acids. Improvement of sensor sensitivities are of great attention, since it allow minimizing the size of the sensor and are desirable for the fabrication of implantable biosensor for continuous glucose monitoring. Nanocarbon, such as carbon nanotube and graphene are known to have high electroconductivity. Moreover, Prussian blue (PB) is an efficient redox mediator with the highest catalytic activity toward hydrogen peroxide reduction. In this study, we attempt to prepare an electrode, which both nanocarbon and Prussian blue are immobilized together with enzyme, glucose oxidase, to obtain a glucose sensor with high sensitivity. In order to immobilize the enzyme together with nanocarbon and Prussian blue, firstly, dispersed aqueous solution of nanocarbon and Prussian blue were prepared using gelling agent Gallen gum. Secondly, electrodeposition was performed using this solution on the platinum electrode, by applying a constant potential of 1.3 V (vs. Ag/AgCl). Finally, the electropolymerization of 0-phenylenediamine was carried out by applying a constant potential of 0.7 V (vs. Ag/AgCl), which will increase the stability of the electrodeposited film by comprehensive polymer film formation. After the enzyme immobilization, the electrode was soaked in phosphate buffer solution (PBS) with stirring for three days in order to remove weakly absorbed enzyme on the electrode. In contrast, electrodes without PB and/or nanocarbon were also prepared in the same procedure for comparison. A Quartz Crystal Microbalance (QCM) was employed to investigate the behavior of film formation on the electrode during the electrodeposition. It was evident to see that the electrodeposition of the solution with PB showed ten times higher deposit amount than that without it. The glucose response measurement was performed at an applied potential of 0.6V (vs. Ag/AgCl) in 0.1 M PBS containing 0.1 M sodium chloride at 40 ˚C. All prepared GOx-immobilized electrodes showed good response toward the addition of glucose, while the electrode containing both PB and carbon nanotube provided the highest response current with good long-term stability.