A highly selective fluorescent probe for hydrogen polysulfides in living cells based on a naphthalene derivative.

Hydrogen polysulfides (HS, n > 1) are members of reactive sulfur species (RSS) and signaling molecules derived from hydrogen sulfide (HS). Recently, the functions of HS in physiological and pathological processes have been increasingly recognized. However, their biological effects and detailed mechanisms of action are still little known. Therefore, there is an urgent need to develop highly selective and sensitive techniques for monitoring hydrogen polysulfides (HS) in living cells. In this study, we designed and synthesized a fluorescent probe based on a naphthalene derivative for the detection of hydrogen polysulfides. A naphthalene derivative was applied as the fluorescent main structure and the 2-fluoro-5-nitrobenzoate group was chosen as the recognition unit. In the absence of hydrogen polysulfides, the fluorescent probe displayed almost no fluorescence. In the presence of hydrogen polysulfides, the fluorescent probe exhibited strong fluorescence. The sensing mechanism was based on HS-mediated aromatic substitution-cyclization reactions. The linear range of the response concentration of the probe to hydrogen polysulfide was acquired in a concentration range of HS from 7.5 × 10 to 2.5 × 10 mol L. The detection limit was evaluated to be 5.0 × 10 mol L for HS. The fluorescent probe can applied in a wide pH range including physiological condition pH. The fluorescent probe showed high specificity for HS over other reactive sulfur species (RSS). Moreover, the fluorescent probe has been successfully applied to confocal imaging of hydrogen polysulfides in HepG2 cells without cell cytotoxicity. All of such good qualities indicated that it could be used to detect HS in living cells.