Lysosome-targeted dual-locked NIR fluorescent probe for visualization of H₂S and viscosity in drug-induced liver injury and tumor models

Background: Lysosomes, as an indispensable subcellular organelle have numerous physiological functions closely associated with H₂S and viscosity, and accurate assessment of H₂S/viscosity fluctuations in lysosomes is essential for gaining a comprehensive understanding of lysosome-related physiological activities and pathological processes. The previous single-response fluorescent probes for either H₂S or viscosity alone have the potential to generate "false positive" signals in a complex biological environment. In contrast, dual-locked probes can simultaneously respond to multiple targets simultaneously, which could effectively eliminate this defect. Therefore, it is essential to constructed a lysosome-targeted dual-locked NIR fluorescent probe for imaging H₂S and viscosity.

Results: In this study, we developed a lysosome-targeted dual-locked NIR fluorescent probe (LFP-N₃) for imaging H₂S and viscosity based on an integrated ICT-TICT process. In the presence of both H₂S and high viscosity conditions, the azide moiety of LFP-N₃ reacts with H₂S, resulting in the formation of LFP-NH₂ that facilitates the ICT process; high viscosity condition further restricts the chemical bond rotation of LFP-NH₂, which suppresses the TICT process. As a result, the fluorescence signal of LFP-N₃ is significantly enhanced at 690 nm with a large Stokes shift (190 nm). Cytotoxicity assay and colocalization experiments in living cells indicated LFP-N₃ possessed low cytotoxicity and precise lysosome-targeted capability. Moreover, both in vitro and in vivo experiments further validated that the fluorescence signal of LFP-N₃ can be triggered by the presence of both H₂S and high viscosity in tumor and drug-induced liver injury models.

Significance: The lysosome-targeted dual-locked NIR fluorescent probe has been successfully utilized to imaging H₂S and viscosity in vitro and in vivo. Compared with the single-response fluorescent probes, the dual-locked NIR probe (LFP-N₃) could effectively mitigate false-positive signals and increase spatial resolution, and has great potential to be developed as a novel diagnostic agent for lysosome-related diseases.