A Meldrum's acid-based covalent-assembly fluorescent probe for rapid and sensitive hydrogen sulfide detection

Hydrogen sulfide (H₂S) is an endogenous gaseous signaling molecule involved in various physiological regulatory functions and pathological processes. Therefore, the development of reliable methods for sensitive and selective H₂S detection is highly desirable. In this study, a novel Meldrum's acid-based covalent-assembly fluorescent probe, CA-H₂S, was developed for the rapid and highly sensitive detection of H₂S. CA-H₂S employs a 2,4-dinitrophenyl (DNP) moiety as the recognition unit. Upon reaction with H₂S, the DNP group is cleaved through nucleophilic aromatic substitution, triggering intramolecular cyclization and rearrangement to generate a highly emissive coumarin fluorophore in situ. CA-H₂S produced an approximately 250-fold increase in fluorescence intensity in the presence of H₂S and exhibited a high quantum yield of 94%, fast response characteristics, outstanding selectivity, and an ultralow detection limit of 12 nM. Moreover, the probe enabled effective fluorescence imaging of H₂S in living cells and mice, suggesting its promising applicability in biological imaging studies.