Electrochemical determination of uric acid in urine and serum with uricase/carbon nanotube /carboxymethylcellulose electrode

The detection of uric acid in blood and urine is clinically important in terms of suitable diagnosis and self-healthcare. An amperometric thin film biosensor composed of carbon nanotube and uricase enzyme is presented. The CNT is successfully dispersed in aqueous solution with carboxymethylcellulose surfactant. This enables thin film formation by a simple drop-casting layer-by-layer process. The uricase/carboxymethylcellulose dispersed carbon nanotube/gold thin film biosensor shows the best sensing performance compared to that with sodium cholate surfactant in terms of higher current and lower detection potential. The presented procedure shows good performance with neither electron transfer mediator nor complicated process. Cyclic voltammetry exhibited a sensitivity of 233 μA mM⁻¹ cm⁻² at +0.35 V, a linear range of 0.02–2.7 mM, and a detection limit of 2.8 μM. We quantify and graph uric acid data in actual physiological samples (serum and urine) for the first time and detection values showed good agreement with those obtained by a conventional analytical method (enzymatic colorimetry kit).