A spiropyran functionalized fluorescent probe for mitochondria targeting and imaging of endogenous hydrogen sulfide in living cells

Abstract

A turn-on spiropyran functionalized fluorescein derivative (FMC) is developed for targeting HS⁻ in mitochondria. FMC exhibits very weak fluorescence at 525 nm under the excitation of 470 nm in aqueous solution due to its colorless spiropyran form; upon addition of HS⁻, a strong fluorescence enhancement by 6.4-fold is observed with spirocycle-opened merocyanine form and rapid trapping kinetics for HS⁻. FMC has good biocompatibility and high selectivity towards HS⁻ with a detection limit of 88.2 nM and is very sensitive among the reported H₂S fluorescent probes. Moreover, the significant colocalization of FMC with Mito Tracker® Deep Red FM in human laryngeal epidermoid carcinoma (HEp-2) cells and the Pearson correlation coefficient of 0.87 together demonstrate that FMC can target and image the endogenous H₂S in the mitochondria of living cells.