Drug Delivery Systems Based on Metal-Organic Frameworks for Tumor Immunotherapy.

Metal-organic frameworks (MOFs) are a class of inorganic-organic hybrid nanoparticles formed by the coordination of metal ions/clusters and organic ligands. Due to their high porosities, large surface areas, adjustable structures, and responsiveness to light/sound, etc., MOFs have shown great clinical potential in the field of tumor therapy. Tumor immunotherapy exerts antitumor effects through reshaping tumor immune microenvironment, showing significant preclinical and clinical advantages. Based on the mechanisms of immunity activation, the tumor immunotherapy agents can be divided into chemotherapeutic agents, immunomodulators, enzymes, tumor vaccines and oligonucleotide drugs, etc. Herein, we review the MOFs-based drug delivery systems for tumor immunotherapy. The classification of MOFs, followed by their antitumor immunity activation mechanisms, are first introduced. Drug delivery systems based on MOFs with different immunotherapy agents are also summarized, especially the synergetic immunity activation mechanisms triggered by MOFs and their loadings. Furthermore, the merits and drawbacks of MOFs and the potential strategies for MOFs to promote their clinical applications are discussed.