الفهرس 
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Abstract
Background: With the development of nanotechnology, silver nanoparticles represent an outstanding nanoparticle product with potential applications in medicine due to its antibacterial effects. Nanoparticles can have wonderful and useful properties, but the same properties may pose a challenge to human health. Genotoxicity is one of the main mechanisms of toxicity to silver nanoparticles, and thus it is critical to assess their potential to cause DNA damage. The aim of the work: The aim of the current study is to assess the genotoxicity of AgNPs on lymphocyte cells of male albino rats using Comet Assay and to study the probability of recovery after discontinuation of exposure. Methods: After preparation and characterization of silver nanoparticles, the current study was performed by injection size (13 ± 3) nanometers of silver nanoparticles into the peritoneal cavity in 40 adult male albino rats at doses of 2 mg / kg for (group I and group Ia and 4 mg / kg for (group II and group IIa) for 28 days as a repeated injection. group Ia and the group IIa were kept for another month to study the possibility of recovery. All of these groups were compared with the control group which were injected with distilled water for 28 days. DNA damage was estimated using comet assay on lymphocytes separated from the albino rat heart using the Comet IV software. Results& Conclusion: There were high significant decrease in the mean of head parameters in both groups I and II compared to the control group and in group II more than group I. There was high significant increase in tail parameters in both groups I and II compared to the control group and in group II more than group I. There was high significant increase in the mean of head parameters in group Ia compared to control and group IIa with high significant decrease in tail parameters in group Ia compared to control and group IIa. Comets were accessed visually and received score from (0-4) for DNA damage index classification which mainly depends on tail intensity (relative propotion of DNA in tail). from the present results, it could be concluded that: Silver NPs was considered to cause harmful effects to human body. DNA damage was revealed to be one of the main mechanisms of AgNPs toxicity. Genotoxicity of Silver NPs developed in a dose dependent manner. Moreover, such damage was demonstrated to be reversible depending on half times which is mainly dependent on dose, size, exposure duration, exposure route and cell type in the experimental trial. Recommendations: Limited utilization of AgNPs containing products to the most indicated ones only. Care should be taken when dealing with AgNPs products especially in terms of occupational work by wearing gloves and protective clothes. Study of the other toxic effects of silver NPs on different organs and the other mechanisms if toxicity. Further studies are needed in the future which include measuring the actual time needed for DNA damage to occur and also the recovery time.