Direct, Pretreatment-Free Surface-Enhanced Raman Scattering (SERS) Detection of Uric Acid in Urine Facilitated by Efficient Hydrogen Bonding-Driven Capture

Uric acid, a vital circulating metabolite, is a key biomarker for various health conditions including gout, preeclampsia, and kidney disorders. This underscores the need for noninvasive, rapid, sensitive, and cost-effective methods for monitoring uric acid to enable early preventive interventions. This study introduces a simple and sensitive separation-free "mix-and-detect" method for the direct surface-enhanced Raman scattering (SERS) detection of uric acid in urine, using bimetallic gold-silver nanostars functionalized with sodium dodecyl sulfate (BGNS@SDS). The SDS capping layer facilitates efficient uric acid capture through multiple hydrogen bonds under alkaline conditions, as confirmed by density functional theory (DFT) analysis. Using the optimized nanostar morphology (BGNS-3@SDS), uric acid was detected in water and spiked artificial urine samples with limits of detection of 2.2 and 3 μg/mL, respectively. These detection limits are substantially lower than the clinically relevant concentration range of uric acid in urine and well below the pathological threshold (∼750 μg/mL). The platform also successfully quantified uric acid levels in urine from ten healthy volunteers without sample pretreatment, enabling differentiation between healthy individuals and those at risk. This straightforward and sensitive SERS strategy holds strong promise for rapid, point-of-care diagnostics targeting low-affinity biomarkers.