A Nanofluorescent\nProbe for Evaluating the Fluctuation\nof Aminopeptidase N in Nonalcoholic Fatty Liver Disease and Hepatic\nFibrosis

Aminopeptidase N (APN/CD13) is a\nwidely expressed transmembrane\nectoenzyme that is crucial for maintaining normal physiological activities.\nIt exhibits abnormal activity closely associated with hepatic fibrosis\nand nonalcoholic fatty liver disease (NAFLD). Therefore, there is\na high demand for noninvasive detection of aminopeptidase N (APN)\nin the diagnosis and research of related diseases. Here, we developed\na small molecule fluorescent probe, Hcy-APN, which is a fluorescent\nprobe with high sensitivity and selectivity for the detection of APN.\nFurthermore, we synthesized the fluorescent nanoprobe Hcy-APN@MSN\nby self-assembling Hcy-APN and mesoporous silica nanoparticles in\nsolution using a combination of molecular probe design and nanofunctionalization\nstrategies. The detection limit of this probe was 1.5 ng/mL. Hcy-APN@MSN\nexhibits more stable spectral characteristics compared to Hcy-APN\nand is suitable for detecting APN activity in live cells and mice.\nHcy-APN@MSN was utilized for in vivo and intracellular imaging of\nNAFLD and hepatic fibrosis at different stages, as well as for a systematic\nassessment of APN levels in the liver. The results confirm an elevation\nin the expression levels of APN in NAFLD and hepatic fibrosis models.\nFurthermore, we investigated the inhibitory effect of the APN inhibitor\nbestatin in nonalcoholic fatty liver and hepatic fibrosis disease\nmodels, confirming its regulatory effect on APN levels in cells and\nin vivo in both disease models. Therefore, this study may offer diagnostic\npossibilities for detecting NAFLD and hepatic fibrosis.