Targeted delivery of cathepsin-activatable near-infrared fluorescence probe for ultrahigh specific imaging of peritoneal metastasis

Inadequate cytoreductive surgery (CRS) has been identified as a prognostic factor for poor patient outcomes in cases of peritoneal metastasis. While imaging probes are used to identify peritoneal metastasis to facilitate CRS, many of these probes exhibit high background signals, resulting in a significant delay in achieving a satisfactory tumor-to-normal ratio (TNR) due to prolonged clearance time. In this study, we designed a novel fluorescent probe named Tras-AA-Cy NH2, which enables the relatively rapid imaging of subcutaneous tumors and peritoneal tumors while maintaining a high TNR. Mechanistically, Tras-AA-Cy NH2 exhibits selective targeting towards the Human epidermal growth factor receptor 2 on the surface of cancer cells. Following internalization, it undergoes enzymatic cleavage catalyzed by the overexpressed cathepsin, leading to the subsequent release of near-infrared fluorophores. Consequently, Tras-AA-Cy NH2 achieved a TNR of 7.8 at 6 h and 21.4 at 24 h in subcutaneous tumor mice. Even after 522 h of in vivo circulation, the TNR remained above 5, indicating an ultralong imaging time window. It is noteworthy that Tras-AA-Cy NH2 has demonstrated successful utilization for peritoneal tumor-specific imaging and further affirmed its tumor tissue-specific recognition capability using human resected tissues. In summary, these findings underscore the rational design of Tras-AA-Cy NH2 for visualizing peritoneal tumors.