A new designed biosensor for the uric acid determination

Uric acid is the end result of the catabolism of the purines in humans. The amount of uric acid in biological fluids is important in the diagnosis of many diseases. These diseases are diseases such as gout disease, Lesch-Nyhan syndrome, kidney disease and Von Gierke's disease. Because of these reasons, uric acid determination is of great medical importance. Today, different colorimetric, chromatographic and spectrophotometric methods are used for determination of uric acid. However, biosensor based methods are preferred because they are generally time consuming and costly systems. The most important advantage of biosensors over other methods is that they are economical, practical and specific for the substances to be determined. In this study, a new amperometric biosensor was developed for uric acid determination. In this study for the determination of uric acid, uricase enzyme on the graphite electrode by using BSA/gelatin and crosslinking by glutaraldehyde. Measurements were carry out at 0,1 V. During the optimization studies the amount of gelatin, bovine serum albumin and glutaraldehyde were determined. For the optimization working condition pH, temperature, scanning rate and buffer concentration were carry out. Afterwards, some parameters such as linearty, repeatability of the measurements and shelf life were carry out. From the bioactive layer optimization studies; gelatin, bovine serum albumin amount and optimal percentage glutaraldehyde were determined as 0,45 gr, 0,030 gr and % 2,5 for the BSA-Gelatin/uricase/glutaraldehyde modified biosensor. Asetat buffer of pH 6,5 and 0,1 M, scanning rate of 0,05 V/s, temperature 35 OC were determined as a optimum working conditions. It was determined that limit of detection 2,5×10-7 M and linear results are obtained between the ranges of 2,5×10-7 − 5×10-3 M for üric acid concentration. As for shelf life studies, at the end of 40th day of response has been preserved by 82,5%, repeatability of the measurement (n=15) standard deviation (SS) = 0,1 and % coefficient of variation ( VK) = 0,2 respectively. Key Words: Uric acid biosensor, Graphite electrode, Uricase, Amprometri