| As immunotherapy has been intensively investigated,it has played an indefinable role in fighting tumor progression.However,the presence of immunosuppressive cells in the tumor microenvironment such as M2-type macrophages,myeloid-derived suppressor cells(MDSCs),and regulatory T cells(Tregs)limits the immune response.Pyroptosis has received widespread attention as a novel mode of programmed cell death(PCD)capable of reversing the immunosuppressed tumor microenvironment(TME).Normally,the gasdermins protein family lowly expressed in tumor cells.However,during pyroptosis,activated cysteine protease-3(caspase-3)specifically cleaves gasdermin E(GSDME)and causes membrane perforation to releases pro-inflammatory cytokines with tumor-associated antigens,thereby activating antigen-specific T cell proliferation and inducing potent anti-tumor effects.How to induce pyroptosis for efficient tumor immunotherapy by precision delivery is the key issue to be solved.The development of nanomedicine has improved tumor therapeutic effect by increasing drug stability and solubility and prolonging drug halflife.However,passive targeting strategies have insufficient targeting ability to tumors,and it is difficult to escape being eliminated by the immune system as foreign substances.The biomimetic delivery systems is expected to solve these problems.Macrophages,as natural immune cells and antigen-presenting cells,have the natural ability to phagocytose particles and target to tumors.The macrophages-based biomimetic delivery system has a powerful application potential.In addition,the decoration with fluorescent photosensitizer new indocyanine green IR-820,could achieve precise navigation and photothermal treatment of the biomimetic delivery system,enhancing the combined photothermal-immunotherapy for tumor.In this paper,the multifunctional macrophage-based biomimetic delivery system with photothermal conversion and fluorescence navigation was designed.For the high drug loading rate and pH responsiveness,the metal-organic framework material ZIF-8 was utilized to load the chemotherapeutic drug decitabine(DAC)to synthesize decitabine encapsulated ZIF-8 nanoparticles(DZNPs).Attributed to the powerful phagocytic properties,large amount of DZNPs were encapsulated by the macrophages.Modified with fluorescent photothermal agent IR-820,the multifunctional macrophage biomimetic delivery system was constructed.Through the specific recognition of tumor cells by macrophages,the drug was selectively delivered to the inside of tumor cells.Using triple-negative breast cancer cells as model,targeted delivery was achieved under fluorescence imaging guidance.With near-infrared laser excitation,the macrophagebased bionic delivery system induced tumor cell pyroptosis,achieving combined photothermal and immune anti-tumor efficacy,and reversing the immunosuppressed tumor microenvironment,further forming a long-term memory effect to suppress metastatic tumors.The study is divided into two main sections as follows.In the first chapter,a multifunctional macrophage biomimetic delivery system was constructed,and photothermal-induced pyroptosis was evaluated in vitro to activate the immune response.Taking advantage of the powerful phagocytic properties of macrophages,a multifunctional macrophage biomimetic delivery system(IDN@MC)modified by fluorescent photothermal agent IR-820 and loaded with DZNPs was constructed.The gradual degradation of the pH-responsive DZNPs nanoparticles encapsulated in IDN@MC leads to the gradual polarization of the host cells from the M0 type to the M1 type,which enhances their recognition and phagocytosis of tumor cells,thereby directly delivering the loaded chemotherapeutic drug DAC to the tumor cell.The modification of the fluorescent photothermal molecule IR-820 endows IDN@MC with fluorescent navigation and photothermal therapy,which facilitates realtime tracking of the in vivo process of the biomimetic drug delivery system using fluorescent images and induces photothermal pyroptosis with external laser control.Using 4T1 breast cancer cell as a model cell,we evaluated the photothermal-induced pyroptosis of tumor cells and further assessed the release of inflammatory factor IL-18 and intracellular calreticulin(CRT)eversion in pyroptosis cells,thereby promoting the maturation of dendritic cells(DCs)and activating their ability to present antigens and trigger immune responses.These results suggest that the macrophage biomimetic delivery system IDN@MC can modulate the photothermal-induced pyroptosis of tumor cells,offering the possibility of combined photothermal-immunotherapy of tumors.In the second chapter,the 4T1 tumor-bearing mouse model was constructed to explore the tumor target,and photothermal conversion performance of the biomimetic delivery system IDN@MC,and the therapeutic effect of combined photothermalimmunotherapy of IDN@MC on primary tumors as well as metastatic tumors.With fluorescent navigation of IR-820,the in vivo tumor targeting behavior of IDN@MC was tracked to achieve precise tumor delivery of drugs.Triggered by the external 808 nm NIR laser,temperature at the tumor site was increased to initiate photothermalinduced pyroptosis,activating the immune response and amplifying the immunotherapy.In addition,under laser irradiationm the IDN@MC induced cell pyroptosis could upregulate the expression of pyroptosis-related proteins GSDME and cas-3,and promote the release of various inflammatory factors,such as IL-2,TNF-α,IFN-y,and IL-18 in the tumor microenvironment.Photothermal-induced tumor pyroptosis activates the immune response and reshapes the tumor immune microenvironment.Flow cytometric analysis of tumor tissues showed that the proportion of antigenpresenting cells DCs and M1-type macrophages in the tumor microenvironment were upregulated,the content of immunomodulatory CD4+T cells and tumor-killing CD8+T cells were increased,and the proportion of M2-type macrophages,MDSCs,and Tregs cells were decreased.These results validated that IDN@MC photothermal activation of pyroptosis-induced tumor immunotherapy significantly inhibited the proliferation of the primary tumor.In addition,IDN@MC photothermal activation of pyroptosisinduced tumor immune combination therapy showed an immune memory effect that inhibited systemic metastasis of tumors.In summary,a macrophage-mediated multifunctional biomimetic delivery system IDN@MC is designed,which integrates a fluorescent navigation system,a tumor tropism system,and a drug loading system.The host macrophages act as self-driven"motors" and drug reservoirs with tumor-targeted accumulation activity for precise drug delivery.The modification of fluorescent photothermal agent IR-820 endows IDN@MC with the performance of fluorescent navigation and photothermal therapy.The inherent tumor tropism of macrophages enables precise tumor-targeted delivery under image guidance.The DZNPs as loading capsules could be packaged into macrophages to realize the pH controlled sustained release of DAC,achieving timelapse control of host macrophages differentiation to M1 phenotype.It enables transfer of therapeutic agents IR-820 and DAC to tumor cells by recognizing and phagocytosing tumor cells.Subsequently,external laser irradiation induces local hyperthermia,initiates photothermal chemotherapy,and synergistically triggers pyroptosis of cancer cells.Inflammatory factors released by pyroptotic tumor cells can activate systemic anti-tumor immune responses and inhibit tumor progression and metastasis.It maybe a potential delivery platform for breast cancer therapy and metastasis prevention. |
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