A Poly(L-Arginine)-Based Electrochemical Sensor for Simultaneous Determination of Uric Acid, Tryptophan, and Hypoxanthine

This study presents the development of an efficient and cost-effective voltammetric sensor for the individual and simultaneous determination of uric acid (UA), tryptophan (Try) and hypoxanthine (HX), the three important biomarkers in the human body. The sensor consists of glassy carbon electrode (GCE) modified with the conducting layer of poly(L-Arginine) (p-Arg) prepared by the electropolymerisation of L-Arginine using cyclic voltammetry. p-Arg modified GCE (p-Arg/GCE) provided well-resolved and improved electrooxidation responses for UA, Try, and HX due to the greater electrocatalytic activity and fast electron transfer ability of the polymer layer. The fabricated sensor was characterised using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), Atomic Force Microscopy (AFM), Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Electrochemical Impedance Spectroscopy (EIS) and electroactive surface area calculations. Under optimal analytical conditions, determination of the three analytes was possible over wide linear ranges with the limit of detection of 1.97 × 10−8M, 4.43 × 10−8M, and 8.44 × 10−9M, respectively for UA, Try, and HX. Practical utility of the sensor was successfully verified in synthetic urine and blood serum samples and determination of Try and HX was carried out in dietary supplements and commercially available samples of tea and coffee, respectively.