A naphthalene-based fluorescent probe for ratiometric imaging of lysosomal hydrogen sulfide in living cells

Hydrogen sulfide is an important gasotransmitter that exhibits various functions in physiological processes. We present a ratiometric fluorescence probe (SN-N₃) for H₂S by functionalizing naphthalene imide with 4-(azidomethyl)benzene as a H₂S recognition moiety and morpholine moiety as a lysosomal targeting unit. After reaction with H₂S, the azido moiety is reduced to amine group, and the probe releases the self-immolative linker and regenerates the fluorophore with internal charge transfer effect. SN-N₃ is responsive to H₂S in a ratiometric mode, exhibiting excellent sensitivity and high selectivity. The probe is demonstrated to be localized in lysosomes with high specificity. More importantly, SN-N₃ is successfully demonstrated to image lysosomal H₂S in a ratiometric manner. Our design provides a novel tool to image H₂S in living cells that would hold great potential in exploring various H₂S-related physiological and pathological cellular processes.