Construction Of Two-dimensional Layered Double Hydroxide Nanoplatform And Research On Anti-tumor Synergistic Therapy

Cancer is a major cause of death.At present,the treatment of cancer faces many challenges.The development of nanomedicine benefits from the rapid development of nanotechnology.The application of nano-carriers in the delivery and controlled release of chemotherapeutic drugs can overcome the limitations of chemotherapeutic drugs,such as poor water solubility,strong side effects and lack of targeting.Therefore,many nano-platforms used in tumor diagnosis and treatment emerge as the times require.Layered double hydroxide（LDH）nanomaterials have attracted more and more attention in cancer diagnosis and treatment because of their diverse chemical composition,easy preparation and isomorphous substitution,high load and adjustable size.However,due to the interaction between various biomolecules in the blood and the cationic surface,LDH nanoparticles are easy to gather in the physiological environment and serum,thus limiting their transmission in vivo,especially the accumulation of tumors.Therefore,LDH nanoparticles must maintain colloidal stability in biological solution.In this work,polyethylene glycol（PEG）was used to functionalize LDH nanosheets.PEG can improve the biocompatibility of nanomaterials,improve the stability of nanomaterials,and make nanomaterials have the characteristics of long blood circulation.Then the targeting peptide B3int was modified by amide condensation reaction to make it have active targeting ability.At the same time,the anticancer drug doxorubicin（DOX）and photothermal agent indocyanine green（ICG）were loaded to prepare a nano-delivery system with dual stimulus response.The combined use of DOX and ICG can significantly improve the anticancer effect.In this thesis,we mainly studied the preparation,characterization,drug release,photothermal properties and anti-tumor effect of nanocomposites in vivo and in vitro.（1）layered double hydroxide nanosheets were prepared by hydrothermal method.The original nanosheets were functionalized with H₂N-PEG-NH₂,then the targeted peptide B3int was linked by amide condensation,and finally DOX-ICG@LDH-PEG-B3int was obtained by loading DOX and ICG by electrostatic adsorption.Under scanning electron microscope（SEM）and transmission electron microscope（TEM）,it was observed that the prepared LDH nanosheets had regular hexagonal structure and the particle size was about 68 nm.After the drug was loaded on the LDH nanosheets,the particle size increased slightly,and the size was about 78 nm,but the morphology did not change obviously.The successful preparation of DOX-ICG@LDH-PEG-B3int was verified by UV-vis absorption spectrum,Fourier transform infrared spectrum and thermogravimetric analysis.The drug loading rate of DOX was 18.62%and the entrapment efficiency was 89.62%determined by UV-vis spectrophotometry.The drug release test in vitro showed that DOX-ICG@LDH-PEG-B3int had p H and near infrared（NIR）responsiveness.Photothermal experiments show that DOX-ICG@LDH-PEG-B3int has a concentration-dependent heating trend and good heating effect,and has excellent photothermal stability.（2）In vitro cytotoxicity of DOX-ICG@LDH-PEG-B3int nanoparticles on tumor cells was stronger than that of free DOX in vitro,but almost non-toxic to normal cells.The results of cell uptake assay in vitro showed that DOX-ICG@LDH-PEG-B3int could respond to the microacid environment in tumor cells,so it was easier to stay in tumor cells than in normal cells.（3）In vivo anti-tumor test showed that DOX-ICG@LDH-PEG-B3int nanoparticles could effectively target the B16 tumor-bearing mice.And DOX-ICG@LDH-PEG-B3int nanoparticles can reduce the systemic toxicity of mice and prolong the survival time of mice.The results of H＆E staining and TUNEL staining showed that DOX-ICG@LDH-PEG-B3int nanoparticles can seriously damage the tumor tissue but almost no damage to the normal tissue,and it can significantly reduce the side effects caused by free drug.To sum up,the dual-responsive drug-loaded nanocomposite DOX-ICG@LDH-PEG-B3int has tumor microenvironment responsiveness,active and passive targeting effects,and the loading of ICG makes its materials have photothermal properties.This study shows the in vivo treatment process of DOX-ICG@LDH-PEG-B3int,and the proposed active targeting nanoparticles with dual stimulus response provide a new direction for cancer therapy.