Hydrogel-Based Whispering Gallery Mode Microfluidic Biosensor for Urea Detection

Urea plays a critical role in biomedical diagnostics, highlighting the need for reliable and sensitive detection methods. In this study, we present a whispering-gallery-mode (WGM) microfluidic biosensor that employs an enzyme-functionalized, pH-sensitive hydrogel to realize label-free and highly sensitive urea detection. The biocompatibility of hydrogel preserves urease activity throughout the sensing process, while the high-quality (Q) factor of the WGM microresonator enhances the biological response. The biosensing system can detect the urea concentration of the analyte within 8 minutes and achieve a detection limit of 0.3 mM. Furthermore, the biosensor exhibits exceptional selectivity, overcoming the effect of structurally similar compounds. This novel design, which integrates a hydrogel-encapsulated WGM system, offers a robust and versatile platform for biomolecular detection.