Construction Of Amino Acid-coordinated Self-assembly Nanozymes And Their Biomedical Application

The principle of chemodynamic therapy is to use nano catalysts,such as Fe₃O₄or MnO₂and other metal oxides,to catalyze H₂O₂into highly toxic oxygen active species（ROS）through Fenton or Fenton like reaction,such as hydroxyl radical·OH.Nanozyme mediated chemodynamic therapy has attracted great attention in the biomedical field,but there are still many limitations to be solved.Firstly,most nanozymes exhibit a single peroxidase catalytic activity towards H₂O₂,and the concentration of H₂O₂affects the level of free radicals;Secondly,the single response mode of nanozymes makes it difficult to ensure their high specificity;Finally,nanozymes based on inorganic materials have low biosafety and high toxic side effects.To address the above issues,this thesis utilizes amphiphilic small molecular amino acids and metal ions as structural units,and through coordination driving and weak intermolecular interactions,regulates the self-assembly process from molecules to the nanoscale,achieving the construction of supramolecular nanozymes.The research results obtained are as follows:1.Using Fmoc-leucine（Fmoc-Leu）and Fe²⁺as structural units,intermolecular self-assembly is regulated based on coordination driven and weak interactions such as hydrophobic and electrostatic interactions.Further use the coordination of Fe²⁺and glucose oxidase（GOx）to co assemble to obtain nanozymes,showing the activities of GOx and peroxidase cascade enzymes,enhancing the production of·OH,and achieving starvation-chemodynamic synergistic treatment.The release rate of Fe²⁺from nanozymes in a simulated body fluid environment is 75%,and the loading rate of GOx is 99%.In the MTT experiment,the cell viability of MCF-7 cells was about 10%,indicating good cytotoxicity.MCF-7 cells can effectively internalize nanoparticles and detect high levels of·OH within the cells,achieving a cascade reaction at the cellular level.At the same time,the nanozyme also showed high antibacterial activity against Escherichia coli and Staphylococcus aureus,and the bacterial survival rate was about 20%.2.Using Fmoc-aspartic acid（Fmoc-Asp）,Cu²⁺,and GOx as the monomers,a highly specific cascaded nanozyme for tumors was constructed through coordination and co assembly.Firstly,it is demonstrated that its glutathione oxidase activity consumes highly expressed glutathione（GSH）and converts Cu²⁺into Cu⁺.Secondly,glucose oxidase activity is utilized to consume glucose and produce hydrogen peroxide.Subsequently,the peroxidase activity was amplified through a Fenton-like reaction to produce a large amount of highly toxic·OH.Further load·OH activated prodrug camptothecin ketothiol doxorubicin（CPT-TK-DOX）,utilize the tumor specificity of nanozyme to release DOX and CPT in situ,reduce the high toxic side effects of chemotherapy drugs,and realize the cascade amplification synergistic treatment of starvation therapy,chemodynamic therapy and chemotherapy in situ.The cleavage rate of CPT-TK-DOX is 83%,showing good·OH responsiveness.In the cytotoxicity study of nanozymes,the cell viability of PC-3 cells was 7.5%,while the toxicity to normal cell L02 cells was significantly reduced.In vivo,nanozymes can accumulate at tumor sites with a tumor inhibition rate of 70%,exhibiting good tumor targeting and tumor inhibition effects.