An amperometric uric acid biosensor based on modified Ir-C electrode

The level of uric acid (UA) has a high relationship with gout, hyperuricemia and Lesch-Nyan syndrome. The determination of UA is an important indicator for clinics and diagnoses of kidney failure. An amperometric UA biosensor based on an Ir-modified carbon (Ir-C) working electrode with immobilizing uricase (EC 1.7.3.3) was developed by thick film screen printing technique. This is the first time to report the utilization of an uricase/Ir-C electrode for the determination of UA by using chronoamperometric (CA) method. The high selectivity of UA biosensor was achieved due to the reduction of H2O2 oxidation potential based on Ir-C electrode. Using uricase/Ir-C as the sensing electrode, the interference from the electroactive biological species, such as ascorbic acid (AA) and UA (might be directly oxidized on the sensing electrode) was slight at the sensing potential of 0.25 V (versus Ag/AgCl). UA was detected amperometrically based on uricase/Ir-C electrode with a sensitivity of 16.60 mu A mM(-1) over the concentration range of 0.1-0.8 mM UA, which was within the normal range in blood. The detection limit of UA biosensor was 0.01 mM (S/N = 6.18) in pH 7 phosphate buffer solution (PBS) at 37 degrees C. The effects of pH, temperature, and enzymatic loading on the sensing characteristics of the UA biosensor were also investigated in this study. (c) 2006 Elsevier B.V. All rights reserved.