Specific imaging of intracellular hydrogen sulfide by a positively charged NIR fluorescent probe

The poor water solubility of traditional activatable organic molecular probes usually limits their detection ability in physiological environment. In this work, a positively charged H₂S probe was designed, which exhibited a significantly enhanced responsiveness to H₂S in the aggregated state due to the increased positive charge density on the aggregate surface. Under physiological conditions, the probe could be activated by H₂S with specificity and sensitivity to release near-infrared fluorescence signal. Moreover, endogenous H₂S levels in living cells were successfully monitored by using this probe. We expect that this probe can provide a new strategy for the design of activatable probes to break the limitation of poor water solubility of conventional organic molecular probes.