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A reagentless uric acid biosensor has been realized using Copper implanted tin oxide thin film (Cu:SnO 2 ) based matrix. The biosensing characteristics of implanted matrix have been studied using the electrochemical impedance spectroscopy and cyclic voltammetry. The prepared matrix (Cu:SnO 2 ), because of the presence of Cu, possess redox properties so that the electron transfer from enzyme to the electrode could be accomplished without using any external mediator in the electrolyte. The developed uric acid biosensor exhibits a high sensitivity of about 0.93 mA/ mM and a linear variation in current response over a concentration range from 0.05 to 1.0 mM of uric acid besides high shelf life (~20 weeks). The Michaelis-Menten kinetic parameter (K m ) is found to be relatively very low (0.12 mM), which indicates the high affinity of the fabricated bioelectrode towards the uric acid (analyte). The results highlight the importance of implanted Cu:SnO 2 thin film as an attractive matrix for the realization of reagentless biosensors towards uric acid.

RF sputtered tin oxide (SnO2) thin film matrix has been efficiently exploited for the detection of uric acid. The deposition parameters for SnO2 thin film have been optimized to yield better electrocatalytic properties. A correlation between its electrocatalytic properties with the structural and electrical properties has been made. SnO2 thin film prepared under optimized growth parameter (70% argon in reactive gas ambient of Ar and O2) exhibits higher mobility of charge carrier and high carrier concentration thereby resulting in enhanced charge transfer characteristics. High surface coverage of uricase onto SnO2 thin films (4.28 × 10(-4) mole cm(-2)), low value of Michaelis-Menten constant (km) 0.18 mM, good linearity in detection of uric acid in the range 0.05-1.00 mM and a fast response of 5 s are attractive features of prepared SnO2 thin film based bioelectrodes for efficient detection of uric acid. The nanoporous and rough surface morphology of SnO2 thin film besides its high carrier mobility in comparison to that of ITO is responsible for the obtained enhanced sensitivity (∼700 μA mM(-1)) and improved sensing response characteristics towards uric acid.

The development of a noninvasive test for uric acid has been the holy grail of uric acid detection research over the last decade. In the present work, a novel matrix comprising of a NiO thin film (a biocompatible material) loaded with Ni microdiscs was prepared on an ITO-coated glass substrate (Ni/NiO/ITO) with the help of RF sputtering for the reagentless detection of uric acid. The bioelectrode was fabricated by immobilizing uricase using a physical adsorption technique on the surface of the Ni/NiO/ITO electrode. The prepared matrix was found to be efficient in sensing biological processes occurring on the surface of the bioelectrode (Ur/Ni/NiO/ITO) in the presence of the analyte (uric acid) to obtain an electronic output. The biosensor exhibits a high sensitivity (431.09 μA mM(-1)), low Km value (0.15 mM), high apparent enzyme activity (5.07 × 10(-2) units per cm(2)), high shelf life (20 weeks) and good selectivity for the detection of uric acid over a wide concentration range (0.05 mM to 1 mM) without any external mediator in the PBS buffer. The obtained results are encouraging for the realization of a reagentless uric acid biosensor with efficient sensing response characteristics.

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