A new electrochemical sensor for the detection of uric acid and xanthine based on a carbon paste electrode coated with a metal organic framework

This study presents a simple strategy for developing a new electrochemical sensor based on a carbon paste electrode (CPE) coated with a copper nanotube-based MOF (NT Cu-MOF/CPE) using electrochemical/chemical approaches. This enzyme-free sensor was employed for the selective determination of uric acid (UA) and xanthine (XA) biomolecules in Britton-Robinson buffer (pH 3) individually and simultaneously by differential pulse voltammetry. The electrode surface was characterized using XRD, FE-SEM, EDX, and AFM techniques. Additionally, EIS and CV techniques were employed to investigate the electrochemical behavior of the prepared sensor. The obtained results indicated the facilitated oxidation of UA and XA on NT Cu-MOF/CPE compared to CPE. Under optimized conditions, the simultaneous determination of UA and XA showed a linear dependence of the sensor response on the analyte concentration in the range of 0.25-75.0 μM with detection limits of 0.10 and 0.25 μM for UA and XA, respectively. The sensor sensitivity for UA and XA was found to be 1.16 μA μM^-1 cm^-2 and 1.02 μA μM^-1 cm^-2, respectively. The repeatability of the sensor for six repeated measurements of UA and XA at a concentration of 10.0 μM was 1.3% and 0.5%, respectively. Finally, UA and XA were determined using the developed sensor in biological samples (urine and serum) with acceptable recoveries ranging from 93% to 106%. Furthermore, to assess the freshness of the meat, the XA content in fish meat at different storage times was determined using the developed sensor. The finding demonstrates the excellent potential of the developed sensor for clinical diagnostics and food preservation evaluation.