Enhancing performance of uricase using multiwalled carbon nanotube doped polyaniline

Multiwalled carbon nanotubes (CNT) doped polyaniline (Pani) nanocomposite has been electrochemically deposited onto indium tin oxide (ITO)-coated glass substrate for fabrication of uric acid biosensor. To achieve this, uricase (from Bacillus fastidiosus) has been covalently immobilized onto glutaraldehyde-modified CNT-Pani/ITO and characterized using cyclic voltammetry (CV), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, electrochemical impedance spectroscopy (EIS), etc. CV studies of CNT-Pani/ITO electrode reveals that the system obeys quasi-reversible electron transfer behavior with diffusion coefficient of 2.3346 × 10(-8) cm s(-1) in K3FeCN6. Fabricated uricase-CNT-Pani/ITO electrodes were tested for uric acid detection in buffer and spiked serum samples electrochemically. It was found that fabricated electrode was able to detect 0.01-1.0 mM uric acid using CV and 0.02-0.8 mM uric acid using differential pulse voltammetry (DPV). The enhanced electrochemical performance of this biosensor is due to the high enzyme loading synergistically connected to CNT-Pani nanocomposite leading to improved enzyme characteristics such as Km value of 4.85 × 10(-3) mM L(-1) (about 70 times less than the free enzyme), sensitivity of 43.2 μA mM(-1) for CV-based detection and 8.38 μA mM(-1) for DPV-based detection within response time of 60 s. Fabricated electrodes were able to maintain their electrochemical activity with 60 times reusability and were stable up to 28 weeks when stored at 4 °C.