A novel strategy of designing neutrophil elastase fluorescent probe based on self-immolative group and its application in bioimaging

Neutrophil elastase (NE) is an important regulator of immune response and is widely regarded as a biomarker for inflammatory diseases. To date, all the NE probe is designed by linking pentafluoropropionyl and amino-containing fluorophores through amide bond. This method is limited by the fluorophores, which must contain amino functional groups. To overcome this problem, we use the self-immolative group to convert hydroxyl groups to fluorophores HFC (4-trifluoromethyl-7-hydroxyl coumarin) into amino groups, and to connect recognition groups (pentafluoropropionyl) to construct a novel NE fluorescent probe HFC-NE. Predictably, HFC-NE can detect NE activity selectively and sensitively with many advantages, such as good water solubility and biocompatibility, high fluorescence enhancement and high affinity. Besides, HFC-NE is successfully applied to real-time and specific detection of NE activity in living cells and zebrafish models. These excellent outcomes confirmed that this strategy based on self-immolative group is a useful method to design more NE fluorescent probes.