Ultra-Sensitive Detection and Inhibition of the Metastasis of Breast Cancer Cells to Adjacent Lymph Nodes and Distant Organs by Using Long-Persistent Luminescence Nanoparticles

The metastasis of breast cancer mainly occurs through the axillary lymph node and blood circulation systems. It is extremely difficult to know when the cancer cells start to metastasize; however, early detection of breast cancer metastasis is crucial and challenging to enable surgical removal of the primary tumor and perform a systematic lymphadenectomy to eliminate invasion of the tumor. Herein, we report real-time tracking of the metastasis of orthotopic breast cancer with background-free near-infrared long-persistent luminescence (NIR-PL) imaging, and its guidance for the surgical removal of lymph nodes. The NIR-PL imaging is based on Cr3+/Nd3+ codoped ZnGa2O4 (A-ZGCN) nanoparticles with a superlong afterglow time of more than 15 days. We show that the detection sensitivity of metastasis of cancer cells with the NIR-PL imaging is higher than the classic bioluminescence imaging. We find that the metastasis of breast cancer cells to lymph nodes occurred as early as on the third day after orthotopic inoculation of breast cancer cells and followed an order of the proper axillary lymph node (PALN, day 3) > accessory axillary lymph node (AALN, day 6) > accessory mandibular lymph node (AMLN, day 9) > mandibular lymph node (MLN, day 25). In addition, we show that the NIR-PL nanoprobes (i.e., A-ZGCN NPs) displayed 17% radioenhancement, which was used for radiotherapy of orthotopic breast cancer to further prevent and reduce its metastasis to other organs. The radiotherapy treatment is superior to surgery for removal of the tumor accompanied by a NIR-PL imaging-guided lymphadenectomy. Our work demonstrates the great potential of NIR-PL imaging and the corresponding nanoprobes for tracking metastasis of cancer cells and for radiotherapy.