Non-enzymatic uric acid sensing in urine using Ag/rGO@PEI@GQDs-modified screen-printed electrodes

Uric acid (UA), the final product of purine metabolism, is an important clinical biomarker associated with several pathological conditions, including hyperuricemia, gout, and neurological disorders. Therefore, accurate monitoring of UA is of significant diagnostic relevance. However, UA determination in blood requires complex pretreatment procedures, whereas urinary UA analysis is simpler due to its predominantly free-dissolved state. In this context, non-enzymatic electrochemical sensors have emerged as promising alternatives to conventional analytical methods, offering rapid response, operational simplicity, and potential portability. In this study, a novel non-enzymatic electrochemical sensor for uric acid detection is proposed, based on a hierarchical nanostructure composed of graphene quantum dots (GQDs) anchored onto a conductive Ag/rGO@PEI substrate. The designed architecture integrates the high electrical conductivity and structural stability of the Ag/rGO@PEI matrix with the large surface area, rich surface functionality, and electrocatalytic activity of GQDs, resulting in a synergistic platform that facilitates charge transfer and enhances UA oxidation. The sensor exhibited enhanced electron-transfer kinetics, reduced charge-transfer resistance, and a strong electrocatalytic response toward uric acid oxidation. Under optimized conditions, the proposed sensor demonstrated a wide linear detection range from 2.0 to 200 mu M, a low detection limit of 1.9 mu M, good selectivity against common interfering species, high reproducibility, and high stability. Furthermore, the practical applicability of the sensor was validated through the successful determination of uric acid in real human urine samples, achieving satisfactory recovery and precision. These results highlight the Ag/rGO@PEI@GQDs nanocomposite as a promising platform for sensitive, reliable, and non-invasive uric acid detection in clinical diagnostics.