NIR-II Ratiometric Fluorescence Probes Enable Precise Determination of the Metastatic Status of Sentinel Lymph Nodes.

Accurately determining the metastatic status of sentinel lymph nodes (SLNs) through noninvasive imaging with high imaging resolution and sensitivity is crucial for cancer therapy. Herein, we report a dual-tracer-based NIR-II ratiometric fluorescence nanoplatform combining targeted and nontargeted moieties to determine the metastatic status of SLNs through the recording of ratio signals. Ratiometric fluorescence imaging revealed approximately 2-fold increases in signals in tumor-draining SLNs compared to inflamed and normal SLNs. Additionally, inflamed SLNs were diagnosed by combining the ratio value with the enlarged size outputted by NIR-II fluorescence imaging. The metastatic status diagnostic results obtained through NIR-II ratiometric fluorescence signals were further confirmed by standard H&E staining, indicating that the ratiometric fluorescence strategy could achieve distant metastases detection. Furthermore, the superior imaging quality of ratiometric probes enables visualization of the detailed change in the lymphatic network accompanying tumor growth. Compared to clinically available and state-of-the-art NIR contrast agents, our dual-tracer-based NIR-II ratiometric fluorescence probes provide significantly improved performance, allowing for the quick assessment of lymphatic function and guiding the removal of tumor-infiltrating SLNs during cancer surgery.