Preparation Of Functional Nanocarrier For Radiotherapy Sensitization

Radiotherapy plays a key role in clinical cancer treatment and free radicals generated during radiotherapy act as an important role.Excessive free radicals in the cell induce oxidative damage of biological macromolecules?such as DNA,proteins,lipids?to cause cell death,and activate apoptotic signal pathway to induce cancer cell apoptosis.Based on the cytotoxicity of free radicals,we innovatively proposed a strategy for radiotherapy sensitization by enhancing the generation of reactive oxygen species?ROS?during radiotherapy.In this thesis,hollow mesoporous silica nanoparticles and MIL-101?Fe?-NH₂ with porous metal organic framework?MOF?structure were used as nanocarriers and further modified with functional molecules to construct a controlled free radical generation system for radiotherapy sensitization.The main results obtained were summarized as follows:?1?HMSNs was chosen as nanocarrier and percarbamide?PCA?was in-situ synthesized in the mesoporous channels and hollow cavity of HMSNs.Then,chitosan?CTS?was coated onto PCA@HMSNs?PCA@HMSNs-CTS?for p H-responsive release of PCA.The as-prepared PCA@HMSNs-CTS improved the stability of PCA and released more PCA in the simulated tumor microenvironment?p H?6.5?,thereby providing more hydrogen peroxide?H₂O₂?for radiotherapy sensitization.The experimental results showed that the H₂O₂ released from PCA@HMSNs-CTS would be decomposed to ROS?such as HO·,H·?by soft-X-Ray irradiation,then ROS can be generated continuously by autocatalytic free radical chain reactions and remain at a high level accompanied by O₂ generation.Meanwhile,cytotoxicity studies showed that no obvious cytotoxicity was observed when PCA@HMSNs-CTS was applied alone.The intracellular ROS level was significantly elevated and cell viability was decreased dramatically when cells incubated with PCA@HMSNs-CTS and irradiated by soft-X-Ray.In addition,wound healing experiment showed that PCA@HMSNs-CTS effectively reduced the migration ability of tumor cells after soft X-Ray irradiation.?2?MIL-101?Fe?-NH₂ was used as nanocarrier and glucose oxidase?GOx?was transported into tumor cells by loaded in the porous structure of MIL-101?Fe?-NH₂ for catalyzing the decomposition of glucose to H₂O₂in cells.Further surface modification of nanocarrier with bovine serum albumin?BSA?reduced non-specific adsorption during the delivery process and increased the retention efficiency of nanocomposites in tumor tissues.The results showed that MIL-101?Fe?-NH₂-GOx-BSA can efficiently catalyze the decomposition of glucose to produce a large amount of H₂O₂,and unsaturated coordinated Fe in MIL-101?Fe?-NH₂ can catalyze the conversion of H₂O₂to highly toxic hydroxyl radicals?OH·?by Fenton-like reaction.Furthermore,MIL-101?Fe?-NH₂-GOx-BSA combined with soft X-Ray could significantly enhance the ROS generation.The cytotoxicity studies showed that MIL-101?Fe?-NH₂-GOx-BSA with low concentration had little toxicity to normal cells,but caused certain toxicity against tumor cells.Nevertheless,cell viability dramatically decreased to below 15%when incubated with MIL-101?Fe?-NH₂-GOx-BSA and irradiated by soft-X-Ray.Further detection of ROS levels in tumor cells by using DCFH-DA as fluorescent probe showed that only a small amount of ROS was produced in tumor cells when soft-X-Ray was applied alone.The intracellular fluorescence intensity was significantly enhanced when tumor cells incubated with MIL-101?Fe?-NH₂-GOx-BSA and irradiated by soft X-Ray,indicating a higher intracellular ROS level,and hence induced more cellular oxidative damage and enhanced killing effect on tumor cells.