Responsive nanosensor for ratiometric luminescence detection of hydrogen sulfide in inflammatory cancer cells

Gasotransmitter hydrogen sulfide (H₂S), produced enzymatically in body, has important functions in biological signaling and metabolic processes. An abnormal level of H₂S expression is associated with different diseases, therefore, development of novel bioanalytical methods for rapid and effective detection of H₂S in biological conditions is of great importance. In this work, we report the development of a new responsive nanosensor for ratiometric luminescence detection of H₂S in aqueous solution and live cells. The nanosensor (Ru@FITC-MSN) was prepared by immobilizing a luminescent ruthenium(II) (Ru(II)) complex into a fluorescein isothiocyanate (FITC) conjugated water-dispersible mesoporous silica nanoparticle (MSN), showing dual emission bands at 520 nm (FITC) and 600 nm (Ru complex). The red luminescence of the formed Ru@FITC-MSN was quenched in the presence of Cu²⁺. The in-situ generated Ru-Cu@FITC-MSN responded to H₂S rapidly and selectively, showing a linear ratiometric luminescence change in FITC and Ru(II) channels with the H₂S concentration (0.5-4 μM). Limit of detection (LoD) and limit of quantification (LoQ) were determined to be 0.36 and 1.21 μM. Followed by investigation of cellular uptake processes, the utility of the nanosensor for ratiometric imaging of H₂S in live cells and its capability to monitor H₂S levels in inflammatory breast cancer cells were then demonstrated. This study provides a powerful approach for detection of highly reactive and unstable H₂S biomolecules in live systems.