A viscosity sensitive azide-pyridine BODIPY-based fluorescent dye for imaging of hydrogen sulfide in living cells

A viscosity sensitive BODIPY fluorescent probe BDP-N3 with high selectivity for detecting H2S was synthesized and designed. The probe exhibited weak fluorescence in non-viscous media. With the increase of viscosity, the fluorescence intensity and decay time of the probe was enhanced significantly, which proved that it acted as a molecular rotor and could be utilized for the detection of changes in viscosity. Additionally, the probe showed a fast 'turn-on' fluorescence response to H2S with high selectivity. The H2S concentration was directly proportional to fluorescence intensity at 515 nm. Furthermore, cellular imaging experiments revealed that the probe was cell membrane permeable and could be applied for sensing of both H2S and viscosity in a biological system.