Improved performance of polyaniline-uricase biosensor.

Uricase has been covalently immobilized using glutaraldehyde as cross-linker onto electrochemically synthesized polyaniline (PANI) films. These PANI-uricase electrodes have been characterized using spectroscopic, cyclic voltammetry and impedance measurements. The morphology and covalent linkage of uricase lead to high enzyme loading and better shelf life. The value of the Michaelis-Menton constant obtained as 5.1x10(-3) mM L(-1) for the immobilized uricase compared to 3.4x10(-1) mM L(-1) for the free uricase enzyme, suggests enhancement in affinity and/or activity of uricase attached to PANI. The influence of pH, temperature and concentration on electrode activity were studied. The enzyme electrodes were found to retain 95% of activity after 17-18 weeks when stored at 4 degrees C. These electrodes have a response time of about 60 s and have been used to measure uric acid concentration in serum. These PANI-uricase electrodes can be used for about 30 times for electrochemical measurements while retaining about 90% of its activity indicating improved performance.