Investigation On Oral Micro/Nano Drug Delivery System For Enhanced Tumor Combined Chemotherapy Based On Lymphatic Transport

Malignant tumor is a major disease that threatens human life.Among the many ways of tumor treatment,chemotherapy is still the most commonly used method for its low cost,remarkable therapy effect and easy operation.Compared with other ways of drug administration,oral administration is the most convenient and has good compliance.However,the therapeutic effect is limited by the harsh environment in gastrointestinal tract and the obstacles in blood circulation.Some studies have shown that macrophages have great potential in tumor targeted drug delivery system,for they can migrate to tumor tissues under inflammatory recruitment.Herein,a novel micro/nano oral drug delivery system(YGM/PEI/FeNPs-5-Fu)was developed and the oral drug delivery system consists of a YGM outer shell,a PEI intermediate layer,and an Iron nanoparticles(FeNPs)core containing drugs.1)The outer YGM could not only protect the drug-loaded from degradation and clearance in gastrointestinal tract,but also be recognized and uptaken by macrophages,so that the drug delivery system could be loaded into macrophages,then migrate to tumor tissues hitchhiking lymphatic system.2)The PEI is requisitioned to accomplish the FeNPs loaded into YGM by electrostatic adsorption which are both negatively charged.The PEI could also prevent the leakage and degradation of drugs in gastrointestinal tract through the proton buffering effect.3)The FeNPs is benefit for minimally releasing of 5-fluorouracil(5-Fu)into macrophages.On the other hand,FeNPs could induce the ferroptosis of tumor cells and M1 polarization of macrophages,enhance the anti-tumor activity of 5-Fu.The main contents of this study are as follows:1.Preparation and characterization of YGM/PEI/FeNPs-5-Fu.In this study,FeNPs was synthesized by Hubble-bubble method and 5-Fu was loaded into FeNPs to construct FeNPs-5-Fu,then PEI encapsulates FeNPs-5-Fu by electrostatic adsorption to construct PEI/FeNPs-5-Fu,PEI/FeNPs-5-Fu was loaded into YGM by electrostatic action and siphon.Finally,the oral micro/nano drug delivery system(YGM/PEI/FeNPs-5-Fu)was prepared.The results showed that the drug loading efficacy and encapsulation efficiency of FeNPs to 5-Fu were(51.10±2.87)%and(26.24±3.11)%,respectively.The encapsulation efficiency of YGM to PEI/FeNPs-5-Fu were(92.08±2.65)%.The results of stability in simulated gastrointestinal juice in vitro showed that the cumulative release rate of 5-Fu from YGM/PEI/FeNPs-5-Fu was(14.47±1.96)%in simulated gastric juice and(20.38±1.91)%in artificial intestinal juice for 8 h,indicating that YGM/PEI/FeNPs-5-Fu had a good stability in gastrointestinal tract and could effectively protect 5-Fu from release in gastric juice and intestinal juice.2.Study on the antitumor activity of YGM/PEI/FeNPs-5-Fu in vitro.To accomplish the anti-tumor activity of this novel oral drug delivery system,YGM/PEI/FeNPs-5-Fu must be uptaken by macrophages and exert no effect to the normal physiological function of macrophages.Firstly,the mouse macrophage cell line RAW264.7 and mouse peritoneal primary macrophage(PEMs)were used as models to investigate the performance of YGM/PEI/FeNPs-5-Fu.The results showed that YGM/PEI/FeNPs-5-Fu could be efficiently uptaken by different macrophages and have no obvious cytotoxicity to macrophages.Secondly,the mouse colon cancer cell line CT26 was used as model to investigate the anti-tumor activity of YGM/PEI/FeNPs-5-Fu in vitro.The results showed that the drugs can be continuously released from macrophages and then uptaken by tumor cells.The result of cell proliferation assay and Transwell experiment showed that YGM/PEI/FeNPs-5-Fu could inhibit the proliferation and migration of tumor cells,exerting obvious anti-tumor activity.Finally,the mechanism experiments showed that YGM/PEI/FeNPs-5-Fu could promote the M1 polarization of macrophages,increase the level of iron and ROS in CT26 cells,enhance the therapeutic effect of 5-Fu.3.Study on the antitumor activity of YGM/PEI/FeNPs-5-Fu in vivo.In this study,male BALB/c mice were used as experimental animals,and colon cancer mice established by AOM/DSS were used as animal models to investigate the tumor targeting and anti-tumor activity of YGM/PEI/FeNPs-5-Fu.The result of the biodistribution in vivo showed that peyer's patch,mesenteric lymph nodes and inguinal lymph nodes have stronger fluorescence signal compared with intestinal epithelium,indicating that YGM/PEI/FeNPs-5-Fu could be loaded into lymphatic system through peyer's patch.The pharmacodynamic studies in vivo showed that YGM/PEI/FeNPs-5-Fu could effectively relieve the symptoms of colon cancer such as inflammation and diarrhea,reduce the tumor load of colon tissue,significantly inhibit the development of colon cancer,the tumor inhibition rate was 62.75%,exerted obvious anti-tumor effect in vivo.Further studies showed that the drug delivery system could promote the M1 polarization of macrophages,enhance the anti-tumor activity of spleen cells and macrophages,promote the accumulation of iron in tumor cells,produce ROS,reduce the content of GSH and the activity of GPX4,break the redox balance in tumor cells,thus killing tumor cells.Therefore,the anti-tumor activity of the drug delivery system in vivo was related to the synergistic effect of chemotherapy,activation of immune system and ferroptosis.