A lysosome targetable and acidic pH-activated fluorescent probe for two-photon imaging of hydrogen sulfide in live cells and animals

The design strategy of targeted fluorescent probes usually involves modifying the probes with organelle-targeting groups, which then guide the probes to enter specific organelles by the traction of the targeting groups. However, the targeting ability of subcellular localization groups is not perfect, and the target analytes are not specifically distributed within the cells. Therefore, designing novel molecular fluorescent probes for highly specific and selective detection of target analytes within specific organelles is an important research direction that deserves attention. Although multiple high-efficiency lysosomal localization fluorescent probes for H₂S have been developed, the pH range for the fluorescence response of these probes to H₂S does not match the specific acidic range of the lysosome very well. In this work, by analyzing the relationship between the structures of the pH-responsive groups and the response range, excellent acidic pH-activated lysosome-localized fluorescent probes Lyso-NP-DS and Lyso-NP-NBD with a better performance have been developed. After the reaction with H₂S, the fluorescence activation pH ranges of their derivatives were between 2.5 and 5.5, 3.0 and 5.5, respectively. However, this could not only solve the problem of insufficient matching between the pH activation range for the fluorescence response to H₂S and the specific acidic range within the lysosome, but it also shows the characteristics of two-photon excitation and high sensitivity. This effectively avoids the background interference and extracellular fluorescence interference in the lysosome, and an accurate and efficient detection of H₂S within the lysosome is achieved.