Non-enzymatic dual-mode plasmonic framework for robust bioanalyte detection.

Quantitation of biological analytes at point-of-care remains challenging, particularly in complex media with competing species. Uric acid (UA), a clinically significant bioanalyte, is especially difficult to measure due to interference and the limited stability of conventional sensors. This work presents a non-enzymatic dual-mode plasmonic sensing strategy that integrates propagating surface plasmons with localized nanoparticle-driven resonances to enhance interaction strength and improve optical signal definition. The sensing interface features a multilayer nanostructure of gold film, APTES-modified gold nanoparticles, and reduced graphene oxide, providing reinforced light-matter interaction and selective surface affinity. The sensor achieves a high sensitivity of 0.2258°/(mg/dL), a low detection limit of 0.0446 mg/dL, and a high binding affinity of 1451.85 (mg/dL)⁻¹ across UA concentrations of 1-12 mg/dL. Selectivity studies show a pronounced resonance shift of 1.6645°, with interference suppressed to ~ 10% even in mixed solutions. Long-term performance assessments reveal less than 0.3% drift after 30 days, 97.2% sensitivity retention following 10 regeneration cycles, and stability above 90% maintained over 90 days at temperatures exceeding 25 °C. These results demonstrate a robust, regenerable, and interference-resistant platform suitable for real-time UA monitoring and adaptable to other clinically relevant bioanalytes.