Mater. Res. Soc. Symp. Proc. Vol. 1530 © 2013 Materials Research Society DOI: 1 557/op 013 0.1 l.2 .4 An efficient uric acid biosensor based on tin oxide thin film matrix Kashima Arora 1 , Monika Tomar 2 and Vinay Gupta 1 1 Department of Physics and Astrophysics, University of Delhi, Delhi 110007, India 2 Physics Department, Miranda House, University of Delhi, Delhi 110007, India ABSTRACT Uric acid biosensor has been developed using tin oxide (SnO 2 ) thin film. The electrochemistry of the developed thin film based electrode is investigated by using cyclic voltammetry. The obtained results demonstrate that the semiconducting SnO 2 matrix offers a striking electrocatalytic activity to the immobilized uricase towards the oxidation of uric acid and promotes the transfer of electrons from the active sites of enzyme onto the electrode. SnO 2 thin film matrix gives a high sensitivity of 0.2 mA/mM and a shelf life of 20 weeks. Moreover, SnO 2 electrode exhibits excellent selectivity and outstanding analytical stability and reproducibility, which enables a reliable and selective determination of uric acid. The SnO 2 based uric acid biosensor shows a linear variation in a wide range from 0 to 1.0 mM of uric acid concentration and the Michaelis Menten Constant (K m ) is estimated to be 0.28 mM which indicated the high affinity of uricase towards its analyte (uric acid). The results indicate that the SnO 2 thin film matrix offers a new and promising platform for the development of novel biosensors. INTRODUCTION Biosensors have found potential applications in the field of health-care, biological analysis, environment-monitoring, food industries and biological warfare. The recent advances in these fields have led to quick development of various biosensors for a wide range of biological elements. Rapid growth in the development of new materials and improvement; in sensing techniques have led to the evolution of advanced biosensors which have potential application in the field of healthcare, biological analysis, environment monitoring and food industries. Uric acid is an important byproduct in human body and a number of pathological disorders are related to its high concentration in human body. It is an end product of purine metabolism in human body, a number of diseases and pathological disorders are related to its high concentration in body fluids (e.g. serum and urine), such as gout, arthritis, kidney disease, cardiovascular disease, and neurological diseases. Consequently, uric acid determination is of paramount importance in the diagnosis of the diseases caused by disorder of purine biosynthesis and catabolism. As a result, its efficient detection at a first step is very important which requires identification of a suitable matrix having high electron communication feature and high adsorption ability. Besides this, efficient immobilization of a specific enzyme on the electrode surface is also crucial. In the past few years, wide band-gap metal oxide semiconductors (ZnO and CeO 2 ) have gained much attention as a matrix for immobilization of various biomolecules due to their bio compatible nature besides strong adsorption ability and abundance in nature. CeO 2 suffers from the stability problem while ZnO based bioelectrodes offer limited sensitivity. Hence, there is an urgent need to identify an alternate matrix which gives stable and enhanced biosensing response characteristics. Recently, few reports have shown the importance of SnO 2 thin film based matrix for the realization of an integrated biosensor due to its good electrochemical behaviour, oxygen 70