Rapid and Sensitive Detection of Cancer Cells with Activatable Fluorescent Probes for Enzyme Activity

Fluorescence (FL)-guided detection of cancer is one of the most promising approaches to achieve intraoperative assessment of surgical margins. Enzymes, such as aminopeptidase, carboxypeptidase, and glycosidase, whose activities are increased in cancer, have attracted great interest as imaging targets for rapid and sensitive visualization of cancerous tissues with fluorescent probes. Activatable probes, which are initially nonfluorescent but become strongly fluorescent upon rapid one-step cleavage of their substrate moiety by the target enzyme, are especially promising for practical clinical application during surgical or endoscopic procedures due to the highly amplified FL change generated by enzyme-catalyzed turnover at lesion sites. Here, we describe robust protocols for using activatable fluorescent probes targeting cancer-associated enzyme activities to visualize cultured cancer cells, metastatic cancer in a mouse model, and cancerous lesions in surgical specimens from patients.