Study On Oxidative Stress Effect And Mechanism Of Different Silver Nanoparticles

With the rapid development of nanotechnology,nanomaterials are widely used in daily life and medical fields due to their unique physical and chemical properties.Silver nanoparticles?AgNPs?,one of the most widely used nanomaterials,have antibacterial,antiviral,anti parasite features,and can enter human body through the skin,respiratory tract,digestive tract,the potential danger caused to the human body and the environment need to be addressed.The particle size,shape,distribution characteristics and surface coating of silver nanoparticles influence its toxicity and biological effect on the organism.At present,the toxicity mechanism of silver nanoparticles is unclear.Some studies have shown that the toxicity of silver nanoparticles is related to the release of silver ions.And studies show that oxidative stress is one of the toxicity mechanism of silver nanoparticles,they can lead to reactive oxygen species?ROS?in different types of cell gathered in the body,and lead to oxidative stress,and have the phenomenon such as organ injury,autophagy in cell.However,the related research is confined to cellular levels,it is necessary to confirm the effect of oxidative damage and the mechanism of silver nanoparticles.In the present study,ICR mice and Caenorhabditis elegans?C.elegans?were selected to investigate the oxidative damage induced by AgNPs with different sizes and coatings.ICR mice was exposed with different silver nanoparticles by consecutive gavage for 28 d.C.elegans was extended exposed with different silver nanoparticles for 48 h.Then the toxicity and oxidative damage effects of different silver nanoparticles on them were discussed and compared.The toxicity with dose-dependent caused by silver nanoparticles and the relationship between oxidative stress and toxicity of silver nanoparticles were investigated.At last,the mechanism of oxidative damage was further explored.1.Characterization of different silver nanoparticles:The particle sizes of the three diferent kinds of silver nanoparticles of AgNPs-20 nm,AgNPs-50 nm and AgNPs-PVP-20 nm were 20.14nm,49.84nm and 22.08nm respectively,and they were almost the same as the reference particle size of the company given.The hydrated particle size were 542.73 nm,912.34 nm,64.27 nm,and the Zeta potential were-9.51 nm,-8.93 nm,-14.21 nm respectively.The results of transmission electron microscopy showed that AgNPs-PVP-20 nm gathered lessly and dispersed well,AgNPs-20 nm and AgNPs-50nm gatherd severely and disperse less.All three kinds of silver nanoparticles were spherical.2.Study on oxidative damage of silver nanoparticles in ICR mice:ICR mice was exposed to AgNPs-20 nm and AgNPs-PVP-20 nm for 28 d with doses of 10,50,250mg/kg,the control group was 1%HPMC,the positive control group was AgNO₃ with dose of 5 mg/kg,there was no any mice died during exposure and no obvious gender difference.From 21 d of exposed to silver nanoparticles,the mice became unusual,their diet were reduced,the color of hair were dark,the mental state was bad,and the speed of body weight gain was slightly lower.Compared with the control group of HPMC,the organ coefficients of the liver in the groups of AgNO₃ and two kinds of silver nanoparticles were reduced dose-dependently.The organ coefficient of lung and kidney increased dose-dependently.The contents of TP,ALB,GLO,ALT and AST in the high-dose group of AgNPs increased by 17.8%,19.8%,15.1%,6.5%and 59.1%respectively.The contents of TP,ALB and GLO in the middle-dose group of AgNPs-PVP were increased by 25.3%,12%and 33.5%respectively,and the contents of TP,ALB,GLO,ALT and AST in the high-dose group increased by 46.9%,32.1%,66.5%,10.9%and69.7%respectively.In liver,lung and kidney,the contents of MDA in the groups with50,250 mg/kg of AgNPs and all groups of AgNPs-PVP increased dose-dependently.In liver,the activity of SOD in the groups with 50,250 mg/kg of AgNPs and groups of 10,50 mg/kg AgNPs-PVP increased dose-dependently.In lung,the activity of SOD in the groups with 50,250 mg/kg of AgNPs and AgNPs-PVP decreased dose-dependently.In kidney,the activity of SOD had the nonlinear trend of increasing firstly and decreasing then.In liver,the contents of GSH in all groups of AgNPs increased firstly and then desreased.In lung,and the contents of GSH in all groups of AgNPs-PVP decreased dose-dependently.In kidney,there was no significant change in GSH content.The above research showd that the exposure to silver nanoparticles could damage the mental status and weight of ICR mice,and it could cause oxidative damage in liver,lung and kidney,the effects caused by AgNPs-PVP-20 nm were more serious than AgNPs-20 nm.3.Effect of silver nanoparticles on oxidative damage in Caenorhabditis elegans:The longest life span of Caenorhabditis elegans in the group of control was 22 days,the death was found in each dose group of C.elegans.Compared with the control group,the survival rate of all doses in all AgNPs decreased dose-dependently.The relative average life in the groups with 1,10,100 mg/L of AgNPs-20 nm and groups with 1,10,100 mg/L of AgNPs-PVP-20 nm and groups with 1,10,100 mg/L of AgNPs-50 nm decreased by 9%,16%,24%and 11%,18%?26%and 8%,15%,23%respectively,body bends decreased by 9.01%,13.18%,17.97%and 9.26%,19.25%,22.44%and8.39%,11.58%,14.55%respectively,head thrashes decreased by 9.85%,15.85%,38.46%and 30.31%,49.70%,58.00%and 7.23%,10.31%,38.44%respectively.The fluorescence intensity in all groups of all AgNPs increased dose-dependently.The fluorescence intensity and the level of ROS in the group with 100 mg/L of AgNPs-PVP-20 nm was the highest,and the AgNPs-50 nm was the lowest.The contents of MDA increased dose-dependently,the contents of GSH decrease dose-dependently.The above studies indicated that the three silver nanoparticles had an effect on the life span,head thrashes,body bends and oxidative stress levels of the C.elegans,and the order is AgNPs-PVP-20 nm>AgNPs-20 nm>AgNPs-50 nm.4.Study on the mechanism of oxidative damage induced by silver nanoparticles in C.elegans:N2 was exposed to AgNPs-PVP-20 nm for 48 h with doses of 1,10,100mg/L,the expressions of oxidative stress related genes in C.elegans was detected by qRT-PCR.Compared with the control group of HPMC,the expression of mRNA in all groups of ctl-1 was up-regulated,the expressions of mRNA in the groups with 10,100mg/L of ctl-2,ctl-3,isp-1,clk-1,mev-1,sod-5 were up-regulated,the expressions of mRNA in the groups with 10 mg/L of sod-4 was up-regulated,the expressions of mRNA in the groups with 10 mg/L of sod-1 were down-regulated,the expression of mRNA in the groups with 1,10 mg/L of sod-2 and sod-3 was down-regulated,the expression of mRNA in all groups of gas-1 was down-regulated,the expression of mRNA in the groups with 10,100 mg/L of sod-5 was down-regulated,and the difference was statistically significant?P<0.05?.The fluorescence intensity and the expressions of mRNA in all groups of mtl-1,mtl-2 were up-regulated inordinately.The level of ROS was reduced after exposed to MT in C.elegans,so MT could relieve oxidative damage caused by silver nanoparticles.In conclusion,silver nanoparticles had a certain toxic effect on ICR mice and C.elegans,and could lead to the production of oxidative stress with a dose-dependent manner.Silver nanoparticles not only could cause changes of MDA,SOD,GSH and oxidative damage to the weight,liver,lungs and kidneys of ICR mice,but also reduced the lifespan,the frequency of head thrashes and body bends of C.elegans and caused changes of MDA,SOD,GSH.MT could relieve oxidative damage caused by silver nanoparticles,and the up-regulation of the expression of mRNA of mtl-1 and mtl-2 in C.elegans could alleviate the oxidative damage caused by silver nanoparticles.The toxicity of three kinds of silver nanoparticles was AgNPs-PVP-20 nm>AgNPs-20 nm>AgNPs-50 nm.Of course,The smaller the particle size,the greater the toxicity of the nanosilver with PVP coating,and the more obvious the oxidative damage.The study provided a clue for the safety evaluation and mechanism research of silver nanoparticles.