Preliminary investigations on a new disposable potentiometric biosensor for uric acid

In this paper, uricase, catalase, and electron mediator were coimmobilized on the surface of the tin oxide (SnO₂)/indium tin oxide (ITO) glass, to develop a disposable potentiometric uric acid biosensor. The SnO₂ / ITO glass was employed as a pH sensor, fabricated by sputtering SnO₂ thin films on the ITO glass. 3-Glycidyloxypropyltrimethoxysilane (GPTS) was utilized to immobilize uricase, catalase and the electron mediator (ferrocenecarboxylic acid, FcA) on the sensing window. The experimental results reveal that the optimal weight ratio of uricase, FcA to catalase (CAT) is 4:1:2. The sensor responds linearly between 2 mg/dl and 7 mg/dl at pH 7.5, in 20 mM of test solution, with a correlation coefficient of 0.99213. Accordingly, no significant interference was observed when interfering substances, glucose, urea and ascorbic acid, were added to the uric acid solution. Moreover, the recorded voltage was relatively constant during the first 28 days of measurement. Consequently, a potentiometric uric acid biosensor was realized with the advantages of low cost and simple fabrication.