Preliminary investigations on a glucose biosensor based on the potentiometric principle

In this study, an electron mediator and a simple immobilization process are adopted to fabricate a potentiometric glucose biosensor. The enzyme and the electron mediator are immobilized on the surface of tin oxide (SnO2)/indium tin oxide (ITO) glass using a covalent bond method to develop a disposable potentiometric glucose biosensor. The SnO2/ITO glass is a pH sensor fabricated by depositing SnO2 thin films onto an ITO glass. The glucose oxidase (GOD) and the electron mediator (ferrocenecarboxylic acid, FcA) are co-immobilized on the SnO2/ITO glass using 3-glycidyloxypropyltrimethoxysilane (GPTS). This work investigates the coimmobilization of GOD and FcA as a useful approach for enlarging the dynamic range to a glucose concentration of 360 mg/dl, and for improving linearity and sensitivity of the fabricated glucose biosensor. The experimental results indicate that the optimal weight ratio of GOD to FcA is 1:1. The output signal is associated with the pH of the measurement environment and the optimal pH value is pH 7.5.