Study On Antioxidant Activity And Mechanism Of Iron Oxide Nanozymes Modified With Vitamins

Reactive oxygen species?ROS?are substances consisting of oxygen in the body or in the natural environment,which contain oxygen and are active in nature.In normal physiological state,production and removal of ROS are maintained in a state of dynamic balance.Low doses of ROS have the function of signal transduction,promoting cell proliferation,migration and differentiation.However,if the abnormal increase of ROS level leads to the breakdown of redox balance in vivo,it causes oxidative stress and causes severe injuries to the cell macromolecules,such as protein,lipid and nucleic acid.Studies have shown that neuroinflammation,neurodegenerative diseases,aging,cancer and so on are all associated with excessive ROS accumulation in vivo.Iron oxide nanozymes?IONzymes?,which have the advantages of high stability,low cost and high biocompatibility,have been widely used in many fields such as antibacterial and cancer treatment since they were found to have enzyme-like activity.The purpose of this study was to explore the potential of IONzymes modified with vitamin as antioxidants.Therefore,the effect of vitamin modification on the morphology,particle size and enzyme-like activity of IONzymes was firstly explored.Secondly,we characterized IONzymes modified with vitamin B₂?VB₂-IONzymes?and investigated their stability,biosafety,ROS scavenging ability and antibacterial effect.Finally,a mouse oral ulcer model was established and the therapeutic effect of VB₂-IONzymes was tested.The research contents are mainly divided into three parts:1.Synthesis and characterization of IONzymes modified with different vitaminsIn this experiment,IONzymes modified with different vitamins were successfully prepared by solvothermal synthesis.The morphology and particle size of IONzymes modified with vitamin were observed by scanning electron microscopy.It was found that unmodified IONzymes are spherical particles with uniform morphology.After modified with different vitamins,the morphology and particle size of IONzymes has changed to some extend.Then,we examined the peroxidase-like,catalase-like and superoxide dismutase-like activities of IONzymes modified with different vitamins.It was found that most vitamins had a certain enhancement effect on the enzyme-like activity of IONzymes,and the enzyme-like activity of IONzymes modified with vitamin B₂ was the highest.Therefore,we selected VB₂-IONzymes for further study.2.Characterization of VB₂-IONzymes and their antioxidant effect and antibacterial activitiesFirstly,IONzymes modified with different doses of VB₂ were characterized by scanning electron microscopy,transmission electron microscope,energy dispersive spectrometer,X-ray diffraction,X-ray photoelectron spectroscopy and microplate reader.The results showed that compared with the unmodified IONzymes,the morphology of VB₂-IONzymes became irregular with the increase of modified dose,and N elements appeared on the surface,but the crystalline phases did not change.In addition,VB₂-IONzymes had fluorescence characteristic peaks of VB₂.Secondly,the catalytic activity of IONzymes modified with different doses of VB₂ was determined and it showed that the peroxidase-like,catalase-like and superoxide dismutase-like activities of IONzymes modified with 0.5 g VB₂ were the highest.Therefore,we chose IONzymes modified with 0.5 g VB₂ for subsequent experiments and investigated their stability.Then,the cytotoxicity test showed that VB₂-IONzymes had no significant toxicity to HOK and BALB/3T3 cells,and could significantly reduce ROS levels in both cells exposed to hydrogen peroxide,showing strong antioxidant capacity and cytoprotective effect.Finally,we tested the bacteriostatic ability of VB₂-IONzymes.The results showed that VB₂-IONzymes had inhibitory effects on Staphylococcus aureus,Escherichia coli and Streptococcus mutans,indicating that they had killing effeets on both Gram-positive bacteria and Gram-negative bacteria.3.Therapeutic effect of VB₂-IONzymes on oral ulcer modelFirstly,the model of oral ulcer in BALB/c mice was established by burning the tongue with glacial acetic acid,and then treated with VB₂-IONzymes.The experimental results showed that after 6 days of treatment,the ulcer surface of control group mice was still swelling and hyperemia.However,the ulcer area of VB₂-IONzymes treatment group was significantly improved.At the same time,VB₂-IONzymes treatment group had the smallest fluctuation in body weight,indicating that after treatment,the effect of oral ulcer on food intake in mice was significantly reduced.The results of HE staining showed that the epithelial layer of ulcer in control group was destroyed and the inflammatory cells infiltrated seriously.However,reepithelization in the VB₂-IONzymes treatment group was initiated and relatively intact.In addition,IONzymes modified with vitamin B₂ can significantly reduce the level of interleukin-6 and interferon-gamma in the ulcer surface,and the anti-inflammatory effect is obvious.