Research On A New Type Of Freeze-dried Lipid Microsphere Preparation And Its Application Of Sensitization Anti-tumor Immunotherapy

Due to its low cure rate,malignancy have become one of the most serious diseases that threat human life and health.At present,the conventional therapeutics fail to achieve a desired clinical effect.Nanomaterials have received extensive attention due to their unique electrical,optical,magnetic and thermal properties.They facilitate a precise diagnosis of cancer,and promote the accurate and continuous delivery of therapeutic agents to the tumor sites,bearing great significance and broad application prospects in the field of biology.As a result,nanomaterials are widely used in the tumor treatment research.The delivery efficiency and therapeutic effect of nanoparticles are closely related to their fate in vivo,such as the biodistribution profiles,drug release behavior,and pharmacokinetics.Therefore,studying the fate of nanomedicine in vivo is also an indispensable part in the process of developing nanomedicine.Encapsulating chemotherapeutics in nanoparticles for anti-tumor therapy has become a current research hotspot.However,a single mode of treatment is usually insufficient in eliciting desired anti-tumor effect.Therefore,it is of great necessity to develop a reasonable combination therapy to enhance the anti-tumor effect and even inhibit tumor recurrence and metastasis.The use of immune checkpoint inhibitors is becoming a clinical research focus,which is often combined with other therapies in order to exert better therapeutic effects.A large number of researches on the combined treatment of immunotherapeutics and chemotherapy have been carried out clinically,demonstrating remarkably enhanced therapeutic efficacy than any single treatment method.However,there are relatively few studies on which combination treatment method is most suitable for clinical use.The exposure behavior of the drug is closely related to its efficacy in vivo,which will inevitably affect the synergistic effect of combined therapy.In this study,we first developed a safe,simple and highly reductive biocompatible nanosystem by encapsulating extremely high concentration of vitamin E(VE)into nanoparticles formed with phospholipids,and then prepared reductive lyophilized docetaxel lipid microspheres(DTX-VNS)by encapsulating DTX.The nanosystem exhibited a high encapsulation ability for DTX,which could be stably stored at 4? for at least 12 months,and significantly reduced myelosuppression,neurotoxicity and hemolysis caused by DTX,displaying a high biological safety.Mice could tolerate over2-fold higher total dose of DTX after multiple intravenous injections of DTX-VNS,compared to that of the clinical DTX agent(Taxotere).In addition,the in vivo fate of DTX-VNS over time after administration was revealed by F?rster resonance energy transfer(FRET)analysis.Our nanosystem has a higher selectivity and more rapid release of drug in the tumor sites than in normal organs,owing to the higher level of ROS within tumors.Excessive oxidative stress is always related to the serious side effects of chemotherapy.Our highly reduced nanosystem significantly alleviates the oxidative stress of cells and reduces the accumulation of reactive oxygen species(ROS)in the cells,greating reducing the side effects.Compared with Taxotere,DTX-VNS also showed a significantly enhanced anti-tumor effect in various models,which results from the synergistic effect of chemotherapy and VE-mediated immunosuppressive microenvironment alleviation.Our research has constructed a highly reduced nanosystem that can selectively release drugs in tumor cells and inhibit oxidative stress in normal cells,thereby improving efficacy and reducing toxicity,providing valuable clinical applications reference.Next,we selected DTX-VNS,which can specifically release drugs in tumor cells,in combination with the immune checkpoint inhibitor anti-PD-1 antibody(?PD-1)for the treatment of malignant tumors.Aiming at studying the exposure behavior of the nanoparticles and ?PD-1 at the tumor site,we designed three ways to combine with ?PD-1 therapy to achieve the optimum chemotherapy sensitization and immunotherapy.Including the simultaneous administration of DTX-VNS and ?PD-1;first injecting DTXVNS for two days and then injecting ?PD-1;injecting ?PD-1 for two days and then injecting DTX-VNS.The results showed that the ?PD-1 delivered two days post DTXVNS treatment showed the strongest anti-tumor effect in a variety of tumor models,and significantly prolonged the survival time of the mice.Through mass spectrometry,multifactor detection and other methods,it is found that this treatment regime improved the tumor immune microenvironment greatly,resulting in a significantly stronger anti-tumor immune response.This may be related to the maximum therapeutic additive effect caused by such delivery strategy and the efficacy of this additive effect is mainly enlarged by the simultaneous exposure behavior of DTX-VNS and ?PD-1 at the tumor site.By analyzing the exposure behavior of drugs in vivo,we have explored the best combination treatment plan for our nanoparticles and immunotherapy,which provided a valuable reference for the reasonable combination of chemotherapy and immunotherapy in the clinic.