Dual-Mode FL-SERS Biosensor for Self-Validating H₂S Detection in Complex Matrices and Mitochondria-Targeted Cellular...

Hydrogen sulfide (H₂S) plays dual-faced roles in physiological regulation and food quality, demanding detection tools with high sensitivity, specificity, and self-validating capability. Herein, a dual-mode biosensor integrating fluorescence (FL) and surface-enhanced Raman scattering (SERS) is developed for ultrasensitive detection and mitochondrial-targeted imaging of H₂S. The biosensor is constructed based on an azide-functionalized metal-organic framework (UiO-66-N₃) coupled with gold nanoparticles (AuNPs), where the electron-withdrawing -N₃ group serves simultaneously as an FL quencher and a SERS reporter. Upon H₂S exposure, the selective reduction of -N₃ to -NH₂ triggers an FL turn-on response and a concomitant SERS signal attenuation. This dual-response mechanism allows for quantitative H₂S detection across a wide dynamic range (0.01-500 nM), with detection limits reaching as low as the pM level. Further functionalization with a mucin1 aptamer and a mitochondrial localization sequence empowers tumor-specific mitochondrial targeting and high-fidelity imaging of endogenous H₂S. The biosensor demonstrates robust applicability in complex beer and wine samples and enables real-time tracking of mitochondrial H₂S fluctuations in living cells. This work establishes a versatile and self-validating sensing platform that bridges materials design with practical bioanalysis, highlighting its broad potential in food safety monitoring and biomedical diagnostics.