Uric acid detection via dual-mode mechanism with copper-coordinated nitrogen-doped carbon dots as peroxidase mimics

Monitoring disease-related biomarkers, such as uric acid in human body fluids, is essential for effective disease management and clinical diagnosis. In this study, copper-coordinated nitrogen-doped carbon dots (Cu@N-CDs) were synthesized via a simple hydrothermal method, achieving a remarkable photoluminescence quantum yield of 44.69%. The Cu@N-CDs emitted fluorescence at 460 nm upon excitation at 360 nm, making them highly suitable for sensitive biosensing applications. For uric acid detection, a Cu@N-CDs-based probe was developed and coupled with phenol (ph-OH) and 4-aminoantipyrine (AP-NH₂). In the presence of hydrogen peroxide (H₂O₂), generated through the enzymatic breakdown of uric acid by uricase, ph-OH and AP-NH₂ reacted to form a pink-colored compound. This compound quenched the fluorescence emission of Cu@N-CDs via an inner-filter effect, enabling fluorometric detection. Additionally, for colorimetric detection, the pink compound was quantified by measuring absorbance at 510 nm. The detection strategy utilized the peroxidase-mimetic activity of Cu@N-CDs, which was further enhanced by the presence of Cu. Under optimized conditions, the fluorometric method demonstrated a linear detection range of 0.01-700 μM, while the colorimetric method showed a range of 0.07-700 μM for uric acid. The developed approach proved highly effective in detecting uric acid in human blood serum and urine samples, yielding accurate results with acceptable recovery rates. This dual-mode detection method offers a reliable, sensitive, and cost-effective tool for monitoring uric acid levels, marking a significant advancement in clinical diagnostics and personalized healthcare.