Red Blood Cell‐Facilitated Photodynamic Therapy for Cancer Treatment

Photodynamic therapy (PDT) is a promising treatment modality for cancer management. So far, most PDT studies have focused on delivery of photo­sensitizers to tumors. O 2 , another essential component of PDT, is not artificially delivered but taken from the biological milieu. However, cancer cells demand a large amount of O 2 to sustain their growth and that often leads to low O 2 levels in tumors. The PDT process may further potentiate the oxygen deficiency, and in turn, adversely affect the PDT efficiency. In the present study, a new technology called red blood cell (RBC)‐facilitated PDT, or RBC‐PDT, is introduced that can potentially solve the issue. As the name tells, RBC‐PDT harnesses erythrocytes, an O 2 transporter, as a carrier for photosensitizers. Because photosensitizers are adjacent to a carry‐on O 2 source, RBC‐PDT can efficiently produce 1 O 2 even under low oxygen conditions. The treatment also benefits from the long circulation of RBCs, which ensures a high intraluminal concentration of photosensitizers during PDT and hence maximizes damage to tumor blood vessels. When tested in U87MG subcutaneous tumor models, RBC‐PDT shows impressive tumor suppression (76.7%) that is attributable to the codelivery of O 2 and photosensitizers. Overall, RBC‐PDT is expected to find wide applications in modern oncology.