A microneedle-based SERS sensor for simultaneous detection of pH and uric acid in interstitial fluid

Monitoring biomarkers in interstitial fluid (ISF) offers a compelling alternative to blood analysis for managing chronic metabolic diseases, owing to the high correlation between ISF and blood analyte concentrations. Herein, we reported a biomimetic microneedle (MN) sensor based on Surface-Enhanced Raman Scattering (SERS) for the minimally invasive, simultaneous detection of pH and uric acid (UA). The sensoring platform functionalized with a plasmonic active interface, constructed via the in situ self-assembly of gold nanoparticles (AuNPs). Crucially, this dense AuNP layer serves a dual function: it creates high-density SERS “hot spots” for signal amplification and significantly improves surface hydrophilicity, thereby facilitating the efficient extraction and enrichment of analytes from the ISF matrix. The sensor displayed superior analytical performance for dual UA and pH detection, offering broad linear dynamic ranges and suitable monitoring intervals relevant to physiological conditions. Additionally, this sensor displayed remarkable durability and reusability, successfully completing penetration and signal acquisition in a simulated skin environment. This work presents a robust, multifunctional sensing strategy for the minimally invasive management of gout and other metabolic disorders, paving the way for future in vivo applications.