A method is described for preparation of uricase nanoparticles (100 nm in size) and their direct immobilization onto the Au electrode. The enzyme electrode along with Ag/AgCl as reference and Pt as auxiliary electrode were connected through potentiostat/galvanostat to construct an amperometric uric acid biosensor. The enzyme electrode was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and electrochemical impedance spectroscopy (EIS). The enzyme electrode detected uric acid level as low as 5.0 mu M at a signal-to-noise ratio of 3, within 7 s at pH 8.5 and 40 A degrees C. The biosensor showed a linear working range, 0.005 to 0.8 mM for uric acid with a sensitivity of 0.03 mA mu M-1 cm(-2). The biosensor was evaluated. The biosensor lost only 15 % of its initial activity over a period of 7 months, when stored at 4 A degrees C. The fabricated biosensor was successfully employed for determination of uric acid in human serum and urine.