A benzophenoxazine-based NIR fluorescent probe for the detection of hydrogen sulfide and imaging in living cells

Hydrogen sulfide (H₂S) plays a vital role in regulating many important physiological functions. However, H₂S-containing industrial wastewater is inevitably pumped into the environment which seriously contaminates water supplies and foodstuffs. So it is crucial to develop a single fluorescent probe for H₂S detection with high sensitivity and selectivity. Herein, a colorimetric and turn-on near infrared (NIR) fluorescent probe NRDNP based on benzophenoxazine was designed and synthesized by thiolysis of 2,4-dinitrophenyl (DNP) ether as the specific reaction site strategy to achieve highly specific H₂S detection in living systems. The studies demonstrated that the probe NRDNP exhibited excellent sensing performance toward H₂S with an about 80-fold NIR fluorescence enhancement, a rapid response within 10 min, excellent sensitivity with a detection limit of 19 nM and good selectivity. Furthermore, the NRDNP is an optical sensor which visually changes in terms of the fluorescence colour/intensity upon sensing gaseous H₂S molecules. NRDNP has low cytotoxicity and has been successfully applied in the fluorescence imaging of H₂S in living cells, suggesting that it would be an effective tool for H₂S detection in living systems.