Abstract: Objective:To study the effects of room curing polymethyl methacrylate(PMMA)with nano-silver on the liver tissue and DNA damage of hepatic cells in the mice, and to evaluate the hepatotoxicity of the nanocomposites. Methods:A total of 40 male Kunming mice aged 6-8 weeks were divided into room curing PMMA with nano-silver groups(PMMA-NM groups,72 h extract liquid, 1/2 72 h extract liquid, 1/4 72 h extract liquid),room curing PMMA groups(PMMA groups, 72 h extract liquid, 1/2 72 h extract liquid, 1/4 72 h extract liquid), negative control group, and positive control group(n=5).All mice were treated by gavage with test compounds at the beginning of experiment and 24 h and 45 h after experiment except the positive control agent, the mice in positive control group were treated with ethylmethylsulfone at 24 and 45 h after experiment,and the mice in negative control group were administrated with the same volume of normal saline by gavage. The eyeball blood of mice was collected for biochemistry analysis of liver 3 h after the final administration. The liver tissue was completely removed immediately after the mice were sacrificed and the organ coefficient was calculated. The percentage of tail DNA(%tail DNA), tail length(TL) and Olive tail moment(OTM) were detected by the in vivo comet assay,and the images were analyzed with analysis software of comet assay. Results:Compared with negative control group, the liver coefficient, the alanine aminotransferase(ALT)and aspartate aminotransferase(AST)levels in liver tissue of the mice in various experimental groups had no significant differences(P>0.05); the% tail DNA,TL and OTM in PMMA-NM groups and PMMA groups had no significant differeces (P>0.05).The% tail DNA,TL and OTM of the mice in positive control group were higher than those in negative control group(t=-40.911, P<0.05;t=-16.620, P<0.05;t=32.943, P<0.05). There were no significant differences of the% tail DNA, TL and OTM of the mice between PMMA-NM groups and PMMA groups at the same concentration (P>0.05).There were no significant differences of the%tail DNA, TL and OTM between PMMA-NM groups at different concentrations of extrat liquid(P>0.05). Conclusion:Room curing PMMA with nano-silver doesn't have adverse effects on the liver and its function in the mice, and the results of comet assay indicates that the material has no genotoxicity, showing that the composite has good biocompatibility.

Key words: nano-silver base inorganic antibacterial agent, polymethyl methacrylate, comet assay, DNA damage, genotoxicity