Fabrication of Red Blood Cell-Based Multimodal Theranostic Probes for Second Near-Infrared Window Fluorescence Imaging-Guided Tumor Surgery and Photodynamic Therapy

The therapeutic efficacy of fluorescence image-guided tumor surgery and photodynamic therapy (PDT) is impaired by the penetration depth limitation, low signal-to-noise ratio of traditional first near-infrared window (NIR I) fluorescence and the hypoxic tumor microenvironment. Here, a "red blood cell-based multimodal probe" was proposed to achieve enhanced tumor targeting and retention of fluorescent probes after an intravenous injection, so that second near-infrared window (NIR II) fluorescence bioimaging-guided complete tumor resection and high-efficiency photodynamic therapy could then be realized. Methods: The hexanoic acid ester-modified rose bengal (RB-HA), RGD (Arginine-Glycine-Aspartic) peptide and avidin were covalently coupled onto amine-modified upconversion nanoparticles (UCNPs) via EDC/NHS reaction (UCNPs@RB@RGD@avidin). Afterwards, the complex of ICG with bovine serum albumin (BSA) was loaded into RBCs through hypotonic dialysis (RBC@ICG). Then, the membrane proteins of RBC@ICG were biotinylated by biotin-modified phospholipids (RBC@ICG@biotin). Finally, the RBCp (Red Blood Cell based probe) was obtained by crosslinking UCNPs@RB@RGD@avidin to RBC@ICG@biotin through the interaction of avidin and biotin. The obtained multimodal RBCp was extensively characterized, both in vitro and in vivo, including analysis of chemical, physical and fluorescent features, O₂ delivery ability, tumor accumulation, NIR II fluorescence bioimaging ability, photodynamic therapeutic efficiency, and biosafety. Results: The RBCp experienced efficient tumor targeting and long tumor retention for almost 4 h after intravenous injection, and the superior signal-to-noise ratio at the optimal time window can be used for guiding precise tumor resection under an 808-nm laser irradiation to facilitate lymph popliteal metastasis surgical delineation. Meanwhile, the RBCp can provide laser-responsive O₂ release to enhance the PDT efficiency of popliteal lymph node metastasis under NIR II fluorescence bioimaging guidance. These excellent performances obviously lead to remarkably enhanced synergistic therapeutic effects of tumor surgery and metastatic inhibition. Conclusion: The proposed strategy will develop a new platform to increase surgical resection completeness and improve PDT efficiency, resulting in the successful and complete inhibition of tumor and metastasis, which could offer a promising approach for the clinical translation of malignant tumor treatment.