Strong red fluorescent probe for detecting chymotrypsin activity in vivo and in vitro

Chymotrypsin is a medication that is useful in treating inflammation, edema, expectoration, and corruption. It has a wide range of medical applications. Therefore, it is critical to create a chymotrypsin real-time drug tracking detection approach. The ester bond in the molecule can be severed by chymotrypsin. Intramolecular charge transfer (ICT) recovers when the ester bond in the probe breaks, resulting in fluorescence. As a result, in this research, we built and investigated the "turn-on" fluorescent probe NBD-1, NBD-2, and NBD-3, which are used to detect endogenous chymotrypsin, and explored the effect of molecular chain length on probe sensitivity through density functional theory (DFT) calculation and spectral testing, and screened the best probe NBD-3, which is a rare bright red fluorescence probe. The presence of endogenous chymotrypsin was subsequently discovered for the first time in the liver of mice with NBD-3 probe in confocal imaging of HeLa cells, in vivo imaging of mice, and in vitro imaging of organs in the experiment. This result confirmed that such probes could precisely detect the distribution of chymotrypsin in various organs of the organism. NBD-3's strong performance makes it possible to detect chymotrypsin medications in real time with a robust tool.