Rapid tumor detection via a fibroblast activation protein-alpha activated fluorogenic probe

Fibroblast activation protein-alpha (FAPa) is an extensively known serine protease that participates in various important physiological processes and found to be highly related to tumor progression and invasion, and its high expression level in various human epithelial carcinomas makes it a potential cancer biomarker. However, as a tumor-specific expression enzyme, only a few fluorescent probes targeting FAPa have been reported, and most of these probes possess either a low emission window or a short Stokes shift, which severely obstructs their application in tissue imaging. Thus, it is an urgent need to acquire more suitable FAPa-targeted fluorescent probes for cancer identification. Herein, by incorporating a previously reported fluorophore that possesses a large Stokes shift (>190 nm) and long emission window (650-700 nm) with a specific recognition unit (N-acylated-glycine-proline, Ac-GP) for FAPa, we acquired a "turn-on" biosensor named TMN-AcGP for FAPa activity sensing. Owing to the high sensitivity and improved optical properties of the newly developed fluorescent probe, in vitro cultured cancer cells and ex vivo dissected tumor tissues were successfully detected and distinguished from normal cells and tissues with a high tumor-to-normal ratio rapidly and accurately.