Hydrogen sulfide (H2S) is one of the endogenous regulators of many physiological processes. NIPY-OH based on an imidazo[1,5-α]pyridine has a large Stokes shift, high photostability with green-emission, relatively high fluorescence quantum yield. NIPY-OH could serve as an excellent candidate for the design of fluorescent probes. However, the reported probes cannot sufficiently take advantage of the optical properties of NIPY-OH due to the water-soluble problem. Herein, a new fluorescent probe NIPY-PBA, based on NIPY-OH, was designed for the detection of hydrogen sulfide. By rational design, compared with other probes, we successfully obtained the probe with higher sensitivity (limit of detection = 43 nM) and shorter response time (1.5 minutes) due to better water solubility. NIPY-PBA maintained the excellent optical properties of a 230-fold fluorescence enhancement with a large Stokes shift (208 nm) at the same time. Furthermore, NIPY-PBA was applied for the fluorescence imaging of H2S in living cells with low cytotoxicity, indicating NIPY-PBA has great potential to monitor H2S in biological systems.
