Phenoxazine-based red-emitting fluorescence probe for specific detection and imaging of endogenous neutrophil elastase in vitro and in vivo

Neutrophil elastase is a crucial serine protease, which can be acted as a biomarker of inflammatory-related diseases. Therefore, visual monitoring of NE level is of great significance for studying the occurrence and development of NE-related disease. As far as we know, up till now only five red-emitting fluorescence probes for NE detection with low fluorescent enhancement have been reported. In order to improve the development of NE detection, we developed a novel NE fluorescent probe BP-NE by using a rarely used red-emitting fluorophore BP, which shows extremely high quantum yield. As expected, BP-NE can successfully detect NE activity with low limit of detection, high fluorescence signal-to-noise ratio and high affinity compare with those previous reported red-emitting NE fluorescent probes. More importantly, BP-NE is able to realize quantitative analysis of endogenous NE levels in three different living cell lines (SKOV3, HepG2 and HeLa) and in zebrafish. The results indicate that BP-NE will promisingly facilitate the NE disease research in vitro and in vivo.