Iron Oxide-based Nanocomposite For Dual-modality Imaging Guided Chemical Phototherapy And Anti-tumor Immunotherapy Against Immune Cold Triple-negative Breast Cancer

Background and objective:Triple negative breast cancer（TNBC）lacks of the expression of estrogen receptor（ER）,progesterone receptor（PR）and human epidermal growth factor receptor-2（HER2）,which is not sensitive to routine hormone therapy and antibody therapy.Therefore,it is urgent to develop new treatment strategies.Compared with normal tissue,abnormal metabolism of tumor cells forms a special tumor microenvironment,such as acidic nature,hypoxia,excessive hydrogen peroxide（H₂O₂）and insufficient catalase activity,which is related to the adverse results of surgery,radiotherapy and chemotherapy.In view of these characteristics,we designed a nanocomposite to diagnose cancer and ascertain the treatment time window through dual-mode imaging.Contraposed the characteristics of tumor microenvironment,chem-phototherapy and immunity were used to effectively inhibit tumor growth and metastasis.Research methods:（1）Preparation and physicochemical characterization of superparamagnetic iron oxide nanoparticles（SPIONs）-based nanocomposites（SPIO@NC）:Firstly,SPIONs were synthesized by high temperature solvothermal decomposition.Secondly,the SPIO@NCs were obtained by self-assembly of Pluronic 123 with SPIONs and IR-780 dyes.The particle size,Zeta potential and stability of SPIO@NCs were characterized.The photothermal conversion efficiency of SPIO@NCs were calculated following previous literature reports.The near infrared imagingⅡregion（NIR-Ⅱ）and magnetic resonance imaging（MRI）properties were tested.In addition,the photothermal effect and catalase-like catalytic activity were determined.（2）Cell experiments:Firstly,in order to evaluate the biocompatibility of SPIO@NC,the cytotoxicity was determined by CCK-8 assay.The uptake of SPIO@NC by cells was tested by Prussian blue staining,the observation upon confocal microscope and flow cytometry.The photothermal therapy and ROS generation of SPIO@NC in cells were performed in vitro.In addition,the polarization properties of SPIO@NC on macrophages from M2 to M1 were also tested.（3）Animal experiments:Firstly,Balb/c mice（female,6 weeks old）were used to establish 4T1 breast cancer model,and NIR-Ⅱ/MRI dual-mode imaging were used to find the tumor location and confirm the laser irradiation time.Secondly,after various treatments,the body weights and tumor sizes of mice in each group were measured.The blood,spleens and tumors were collected,and the related immune cells and cytokines were analyzed to evaluate the therapeutic effect.The liver and kidney functions were measured by the biochemical test.The hematoxylin-eosin（H&E）staining of important organs and tumors were performed to analyze the biocompatibility in vivo.Results:SPIO@NC system has excellent NIR-Ⅱand MRI imaging effect and preeminent photothermal effect.It can accumulate tumor by enhancing permeability and retention（EPR）effect,to be a dual catalase-like enzyme to catalyse H₂O₂ to produce ROS and O₂,and induce M2 macrophages to reprogram into M1 macrophages.In the course of treatment,anti-tumor immune cells（M1 macrophages and CD8⁺T cells）were effectively up-regulated,and tumor-promoting immune cells（M2 macrophages,regulatory T cells and bone marrow-derived suppressor cells）were down-regulated,which played an excellent anti-tumor effect,and had no obvious side effects in vivo.Conclusion:we have developed a multi-functional SPIO@NC nanocomposite,which can diagnose tumors and ascertain the laser irradiation time through NIR-Ⅱ/MRI dual-mode imaging,and guide chem-phototherapy and anti-tumor immunity,inhibiting tumor growth effectively.This iron oxide-based nanocomposite provides a promising strategy for the diagnosis and treatment of cancer.