A quaternary ammonium modified fluorescent probe for hydrogen sulfide detection in living cells

Azide-reduction based fluorescent probes are one of the most important methods for H2S detection. However, low water solubility and low sensitivity are common problems encountered by such probes. Herein, five azide-reduction based probes with corresponding hydrophilic moieties (hydroxyl, tertiary amine, and quaternary ammonium) attached were rationally designed and synthesized. After a comparative study of their spectral properties, we found that the quaternary ammonium modified probe H3 showed the total solubility in water and the best reactivity to H2S as well as the lowest detection limit, indicating that the quaternary ammonium moiety not only improved the solubility of the probe, but also had a significant sequestration effect for HS-. A further application of H3 in HeLa cells was also carried out and validated its potential for biological imaging.