Platelet Membrane‐Camouflaged Magnetic Nanoparticles for Ferroptosis‐Enhanced Cancer Immunotherapy

Although cancer immunotherapy has emerged as a tremendously promising cancer therapy method, it remains effective only for several cancers. Photoimmunotherapy (e.g., photodynamic/photothermal therapy) could synergistically enhance the immune response of immunotherapy. However, excessively generated immunogenicity will cause serious inflammatory response syndrome. Herein, biomimetic magnetic nanoparticles, Fe₃ O₄ -SAS @ PLT, are reported as a novel approach to sensitize effective ferroptosis and generate mild immunogenicity, enhancing the response rate of non-inflamed tumors for cancer immunotherapy. Fe₃ O₄ -SAS@PLT are built from sulfasalazine (SAS)-loaded mesoporous magnetic nanoparticles (Fe₃ O₄ ) and platelet (PLT) membrane camouflage and triggered a ferroptotic cell death via inhibiting the glutamate-cystine antiporter system Xc⁻ pathway. Fe₃ O₄ -SAS @ PLT-mediated ferroptosis significantly improves the efficacy of programmed cell death 1 immune checkpoint blockade therapy and achieves a continuous tumor elimination in a mouse model of 4T1 metastatic tumors. Proteomics studies reveal that Fe₃ O₄ -SAS @ PLT-mediated ferroptosis could not only induce tumor-specific immune response but also efficiently repolarize macrophages from immunosuppressive M2 phenotype to antitumor M1 phenotype. Therefore, the concomitant of Fe₃ O₄ -SAS @ PLT-mediated ferroptosis with immunotherapy are expected to provide great potential in the clinical treatment of tumor metastasis.