Photostable Ratiometric Two-Photon Fluorescent Probe for Visualizing Hydrogen Polysulfide in Mitochondria and Its Application

Hydrogen polysulfide (H2Sn) has currently attracted much research interest because it not only plays an important physiological function in many biological and health-related events, but also is considered as a newfound potent signal transducer. Small-molecule-based ratiometric fluorescent probes have advantages in sensitivity and biodetection, but such approaches that are intentionally developed for H2Sn detection and expected to be mitochondria-accessible are still lacking. In this work, because of the triphenylphosphine group introduced into the molecular scaffold of the naphthalimide derivative, Mito-NRT-HP was successfully applied to visualize intracellular H2Sn in mitochondria with excellent aqueous solubility, super photobleaching resistance, favorable cellular membrane permeability, and good biocompatibility. This one- and two-photon fluorescent probe with high selectivity and sensitivity (limit of detection, LOD = 0.01 mu M) evinced a 70-fold enhancement of the fluorescence ratio (I-546nm/I-478nm) in the presence of H2Sn over other reactive sulfur species (RSS). The experimental results also give Mito-NRT-HP the potential for mapping the H2Sn distribution in mitochondria and evaluating the H2Sn roles in more biological processes, and they demonstrated the practical application possibility of Mito-NRT-HP in the early diagnosis of lipopolysaccharide-induced (LPS-induced) acute organ injury.