Hybrid SPR-LSPR Uric Acid Sensor: An Innovative Framework for Ultrasensitive, Selective, and Stable Biomolecular Detection

Accurate and sensitive biomarker detection is vital for modern diagnostics, especially in point-of-care testing (POCT), where real-time analysis is essential. Uric acid (UA), a key indicator of metabolic disorders including gout, nephropathy, and cardiovascular disease, requires precise quantification across physiologically relevant ranges in complex matrices. Conventional UA detection methods suffer from instability, poor selectivity, and susceptibility to interference. This study presents an innovative non-enzymatic hybrid surface plasmon resonance–localized surface plasmon resonance (SPR-LSPR) sensor that combines the long-range sensitivity of SPR with the near-field enhancement of LSPR. The platform incorporates a nanostructured gold-3-aminopropyltriethoxysiane-gold nanoparticle-graphene quantum dots (Au-APTES-AuNP-GQD) matrix, leveraging gold thin films, amine-functionalized AuNP, and GQD to enhance plasmonic confinement and molecular recognition. Structural and optical characterizations confirmed its nanoscale integrity. The sensor achieved a sensitivity of 0.1828°/(mg/dL), a low detection limit of 0.1658 mg/dL, and linearity (R² = 0.8655) across a 1–9 mg/dL UA physiological range. It demonstrated high selectivity, with a 1.1757° shift and 90.1% relative response to UA in the presence of common interferents. This label-free, real-time, and scalable sensor is highly suited for POCT and continuous UA monitoring, with modular adaptability for broader clinical biomarker detection.