A novel lysosome-located fluorescent probe for highly selective determination of hydrogen polysulfides based on a naphthalimide derivative

Hydrogen polysulfides (H2Sn, n > 1) belongs to sulfane sulfur in the reactive sulfur species (RSS) family and plays a significant regulatory role in organisms. Highly selective and lysosome-located probes for detecting hydrogen polysulfides are rare. Thus, it is important to develop a technique to detect the changes of H2Sn level in lysosomes. In this work, a lysosome-targeting fluorescent probe for H2Sn was designed and developed based on a naphthalimide derivative. 4-Hydroxynaphthalimide was selected as the fluorescent group and 2-chloro-5-nitrobenzoate group was used as a specific recognition unit for H2Sn. A morpholine unit was chosen as a lysosome-located group. In the absence of H2Sn, the fluorescent probe exhibited almost no fluorescence. In the presence of H2Sn, the fluorescent probe showed strong fluorescence owing to H2Sn-mediated aromatic substitution-cyclization reactions. The fluorescence emission intensity at 548 nm of the probe showed a good linear relationship toward H2Sn in the range of 2.0 × 10-7 - 9.0 × 10-5 mol·L-1, and the detection limit was found to be 1.5 × 10-7 mol·L-1. The probe possessed a wide work range of pH, including the pH of physiological environment, and high selectivity for H2Sn. There are almost no cytotoxicity and the ability of detecting endogenous and exogenous H2Sn in lysosomes. These results indicate that the fluorescent probe can provide a good tool for intracellular and extracellular detection of H2Sn.