Regulation Of Antioxidant And Pro-oxidation And Biological Application Of MXene

Disease is an important way to threaten human health and life.Inflammation,diseases caused by microbial pathogens,and tumors can be treated by regulating ROS levels.ROS balance is regulated by a variety of enzymes in the human body,but such natural enzymes are expensive,difficult to prepare,easy to deactivate and other disadvantages limit their application.Compared with natural enzymes,nano-enzymes have the advantages of simple preparation and low cost,and can simulate the activity of natural enzymes and regulate ROS content,which has attracted extensive attention from researchers.Thousands of nano-enzymehave been reported so far,including precious metals,metal oxides and sulfides,carbon nanostructured materials and their composite nanomaterials.Among them,two-dimensional MXene nanosheets have gradually entered the field of biological therapy with the advantages of large specific surface area,good biocompatibility and rich surface active sites.In this thesis,the type and abilities of Ti₃C₂and V₂CMXene in scavenging ROS and free radicals were studied,the antioxidant capacity of Ti₃C₂MXene was comprehensively evaluated,and the morphologies,structures and catalytic activity changes of metastable MXene after oxidation were analyzed,which opened up a new field of MXene in the field of disease treatment.The details are as follows:（1）Ti₃C₂MXene was prepared by traditional HF etching and TMAOH intercalation.Two-dimensional Ti₃C₂MXene nanosheets can effectively remove reactive oxygen species and active nitrogen(·OH、H₂O₂、O₂^-·and·NO),ABTS^+·and DPPH·free radicals.It showed concentration-dependent,tunable and broad-spectrum antioxidant activity.Compared with natural antioxidant molecules（AA and TA）,Ti3C2 NSs showed higher antioxidant activity and broad spectrum.We further demonstrated that PEG-modified Ti₃C₂has good stability against oxidative stress in cells.Under 5μg/mL Ti₃C₂-PEG treatment with H₂O₂-induced oxidative stress,the intracellular ROS level decreased by 4 times,and the cell survival rate reached 194%.A synergistic mechanism of oxidation resistance based on gradient oxidation and catalytic performance was proposed.The results indicate that ultra-thin Ti₃C₂MXenes has great potential as an antioxidant in preventing biological damage caused by oxidative stress.（2）Two-dimensional V₂C MXene was prepared by the same method.Two-dimensional V₂CMXene nanosheets also have the ability of spectral scavenging free radicals.The morphology,structure and catalytic activity of V₂CMXene were studied by heating at 30℃and 60℃.The results show that V₂CMXene is oxidized,and the nanosheets are broken and grown into micron VOx nanowires.XRD and XPS showed that V₂C reacted with oxygen in the solution during the oxidation process,and the valence of vanadium increased,mainly V⁴⁺and V⁵⁺.The crystal structure of V₂CMXenedid not change during the oxidation process.In the oxidation process,theability of V₂C to remove free radicals represented by ABTS^+·is weakened,but when V₂C reacts with H₂O₂,it will generate·OH,which is highly toxic,resulting in POD activity.In the evaluation of POD activity of VOx-30 and VOx-60,the comparison shows that VOx-30 has stronger catalytic activity,almost twice as much as VOx-60.Because oxidized V₂C has more defects on its surface and binds more tightly to the bacterial membrane,a very small amount of VOx-30（0.4mg/mL）shows good antibacterial effect.The results showed that the oxidized V₂C had better POD activity than V₂C,showing great potential in antibacterial field.（3）On the basis of V₂C prepared in Chapter 2,V₂Cwas oxidized to VOx-4nanowires about 300 nm in length at 4℃.The combination of VOx-4 and CDs improved the antioxidant activity of VOx-4 and reduced the damage to normal cells.VOx-4 has a good peroxide-like activity,and has a higher catalytic activity in the pH=4 HAc-NaAc buffer solution.In the tumor killing experiment,VOx-4@CDs showed a powerful killing effect on three kinds of cancer cells,providing a new idea for MXene in tumor treatment.This thesis has 27 figures,and 125 references.