AuNPs/reduced graphene oxide biointerface with immobilized uricase for mediator-free electrochemical uric acid...

A simplified, mediator-free electrochemical biosensing platform was developed using a nanostructured gold nanoparticles/reduced graphene oxide (AuNPs/rGO)-modified screen-printed carbon electrode (SPCE) for the detection of uric acid (UA). The proposed system combines the conductive properties of rGO and the electrochemical activity of AuNPs with uricase immobilized onto the nanostructured interface by simple adsorption. The sensing principle is based on the enzymatic oxidation of UA to hydrogen peroxide (H₂O₂), followed by electrochemical oxidation of H₂O₂ at the AuNPs/rGO-modified electrode without an external redox mediator. Differential pulse voltammetry (DPV) measurements showed a linear response over the concentration range of 1.0-100 µM. The limit of detection was 0.30 µM in PBS and 0.24 µM in 1:20 diluted human plasma. The biosensor showed satisfactory reproducibility and storage stability, with an RSD ≤ 5% and approximately 90% signal retention after 14 days at 4 °C. Evaluation in spiked diluted plasma samples yielded recoveries ranging from 96.5 to 103.2%. These results demonstrate the feasibility of the proposed uricase-based, mediator-free configuration for UA determination in a diluted biological matrix.