A novel aminopeptidase N triggered near-infrared fluorescence probe for imaging enzyme activity in cells and mice

Aminopeptidase N (APN) is an important proteinase, and the abnormal level of APN is closely related to many diseases. Thus, the specific detection and tracking of APN activity is of great significance in the fields of clinical diagnosis and drug development. Herein, we designed and synthesized an APN-activated near-infrared (NIR) fluorescent probe ZY-APN and successfully applied it for in vitro and in vivo enzyme detection. Linking L-alanine recognition moiety to the xanthene dye through amide bond endowed ZY-APN with specific response towards APN without being influenced by other bio-species. After reaction with APN, the probe exhibited a notable NIR fluorescence enhancement at 730 nm. With this probe, we could distinguish between normal cells and tumor cells due to the differences of APN activity. Besides, we have realized the visualization of high expression of APN in tumor-bearing mice. Hence, probe ZY-APN may display potential application in the diagnosis and treatment of APN-related diseases, especially cancer.