Development of a Rapid-Response Fluorescent Probe for HS: Mechanism Elucidation and Biological Applications.

Hydrogen sulfide (HS) is an important signaling molecule involved in various physiological and pathological processes, making its accurate detection in biological systems highly desirable. In this study, two fluorescent probes ( and ) based on 1,8-naphthalimide were developed for HS detection via a nucleophilic aromatic substitution. demonstrated high sensitivity and selectivity for HS in aqueous media, with a detection limit of 0.64 µM and a strong linear fluorescence response in the range of 0-22 µM of NaHS. The reaction kinetics revealed a rapid response, with a reaction rate constant of 7.56 × 10 M s, and was most effective in the pH range of 6-10. Mechanism studies using H NMR titration confirmed the formation of 4-hydroxyphenyl-1,8-naphthalimide as the product of HS-triggered nucleophilic substitution. was applied in MDA-MB-231 cells for cell imaging, in which provided significant fluorescence enhancement upon NaHS treatment, confirming its applicability for detecting HS in biological environments. In comparison, , designed with extended conjugation for red-shifted emission, exhibited weaker sensitivity due to the reduced stability of its naphtholate product and lower solubility. These results demonstrate that is a highly effective and selective fluorescent probe for detecting HS, providing a valuable resource for investigating the biological roles of HS in health and disease.