The Oxidase-like Activity Of Selenium Nanoparticles With Different Surface Charge And Its Effect On Atherosclerosis

Selenium is an essential micronutrient for human body.It has many functions in life,such as delaying aging,scavenging free radicals,protecting cardiovascular system,anti-cancer and so on.However,due to the narrow range of safe and toxic doses of traditional selenium supplements,the application of selenium in health food and medicine is limited.Selenium nanoparticles?SeNPs?is a new form of selenium developed in recent years.Compared with traditional selenium compounds,SeNPs has unique physical and chemical properties,which can not only play the unique functions of inorganic selenium and organic selenium,but also have low toxicity.A large number of studies have shown that SeNPs have multiple biological functions such as antioxidant,hypoglycemic and so on,which means that it may have the effect of slowing down atherosclerosis?AS?.In this paper,three kinds of surface charge SeNPs were prepared by different wet chemical reduction methods,and whether SeNPs have simulated oxidase activity was discussed.Then we compared the relationship between different SeNPs and simulated oxidase,and deduced the possible catalytic mechanism.Secondly,a simple and fast colorimetric method for the detection of Hg²⁺was established by using simulated oxidase activity.Finally,apolipoprotein E?ApoE?gene knockout mice fed with high-fat diet were used as AS models to study the effects and mechanisms of different surface charge of SeNPs on AS lesions.Red amorphous BSA-SeNPs were prepared by chemical reduction of sodium selenite with reduced glutathione?GSH?as reducing agent,bovine serum albumin?BSA?as protective agent.The size distribution of the red amorphous BSA-SeNPs was fairly uniform?38.1±4.8 nm?.The amorphous CS-SeNPs and SA-SeNPs were prepared by using vitamin C as reducing agent,chitosan and sodium alginate as protective agent.The size distributions of the amorphous CS-SeNPs and SA-SeNPs were 75.6±6.5 nm and 64.6±10.9 nm,respectively.Three kinds of SeNPs can catalyze the oxidation of substrates 3,3'5,5'-tetramethylbenzidine?TMB?,and all of them have oxidase-like activities.Among them,the optimum reaction conditions of BSA-SeNPs,CS-SeNPs and SA-SeNPs were pH 4,3.5,4,30?C,20?C,and 25?C,respectively.The simulated oxidase activities of three SeNPs showed a concentration-dependent relationship.The kinetic parameters of BSA-SeNPs and CS-SeNPs simulated oxidase were compared.The Michaelis constant?K_m?and maximum reaction rate(V_max)were 0.749 mM,0.729 mM,2.90×10^-7M/min and 1.216×10^-6M/min,respectively.The results showed that the catalytic rate of CS-SeNPs was faster and the activity of simulated oxidase was higher than BSA-SeNPs.In studying the mechanism of CS-SeNPs catalytic reaction,it was found that the inhibition rate of reaction reached 80%when O^2-·trapping agent was added and about 40%when·OH trapping agent was added.Moreover,the formation of O^2-·?·OH in the reaction system was also detected by ESR.In summary,we propose a possible catalytic mechanism that SeNPs first catalyzes the conversion of oxygen into O^2-·and OH.TMB was then oxidized from colorless to blue by O^2-·and·OH.?The simulated oxidase activity of CS-SeNPs can be significantly inhibited by mercury ion(Hg²⁺).Based on this phenomenon,a simple and rapid colorimetric method for detecting Hg²⁺has been established.The method showed good sensitivity and selectivity,and showed good linearity in the range of 0-2.5 um Hg²⁺concentration,and the detection limit reached 120 nm.To study the effects of different SeNPs on apolipoprotein E?ApoE?gene knockout mice,40 8-week-old male ApoE^-/-mice were randomly divided into 5 groups,as well as KO group,sodium selenite group,BSA-SeNPs group,CS-SeNPs group and SA-SeNPs group.10C57BL/6J male mice were used as blank control group.The mice were fed with Western diet.The doses of Na₂SeO₃,BSA-SeNPs,CS-SeNPs and SA-SeNPs were 50 ug/kg.bw.The KO group and the blank control group were given the same volume of physiological saline.After 24 weeks of continuous administration,they were executed.Four indexes of serum lipid were detected:total cholesterol?TC?,triglyceride?TG?,high density lipoprotein?HDLC?,low density lipoprotein?LDLC?,oxidative stress level:glutathione peroxidase?GPx?,reduced glutathione?GSH?,total superoxide dismutase?T-SOD?,malondialdehyde?MDA?,and the function of tissues and organs:alanine aminotransferase?ALT?,glutamic oxaloacetic transaminase?AST?,urea nitrogen?BUN?,creatine kinase?CK?.Meanwhile,the aorta was stained with oil red O,and the aortic arch and liver of mice were stained with pathological sections.The activities of T-SOD and GPx and the contents of MDA and GSH in the liver of mice were detected.Real-time fluorescence quantitative PCR was used to investigate the expression of lipid metabolism,inflammatory factors and other genes in liver.The results showed that long-term selenium supplementation could promote oxidative stress in mice and further aggravate atherosclerosis in ApoE^-/-mice.The myocardial function,liver function and kidney function of Na₂SeO₃ group were damaged to varying degrees,among which the myocardial function was the most serious;the CS-SeNPs group had a serious tendency in myocardial function compared with KO group;the SA-SeNPs group had a serious tendency in renal function compared with KO group;the BSA-SeNPs group had a serious tendency in myocardial function,liver function and kidney function compared with KO group.There is a tendency to become more severe,and liver and kidney function are the most serious in each group.