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Subacute effect of ZnO nanoparticles on primary damage DNA induction with emphasis on structural integrity and copy-number of TP53 gene

ZnO nanoparticles are one of the most widely present nanomaterials in human life. Their antimicrobial properties and contribution to mechanical properties of final products made them inevitable in food industry, medicinal and dental materials. Small in size and large in surface area, nanoparticles may interact with macromolecules in unexpected way inducing adverse health effects. To evaluate genotoxicity of ZnO nanoparticles (< 35 nm in diameter), we treated extended-term human lymphocyte cultures for 14 days at final mass-concentrations of 0.1, 1.0, 2.5, 5, and 7.5 µg/L. This approach enabled exposure to ZnO nanoparticles during entire cell-cycle and direct contact with genome in mitosis. Primary DNA damage was measured by alkaline comet assay. To assess potential impact on structural integrity and copy-number of TP53 gene we hybridized comet slides with TP53 deletion DNA probe in comet-FISH. We detected concentration dependent, though insignificant increase in percentage of DNA in comet-tails of ZnO treated lymphocyte (ranging from 2.4 ± 4.9 to 3.9 ± 3.1%) compared to the control (0.9 ± 1.2%). Opposite, ZnO nanoparticles at concentrations of 2.5, 5, and 7.5 µg/L significantly elevated TP53 fragmentation rate (36.6 ± 4.7, 40.0 ± 4.7, 35.0 ± 7.1%, respectively vs. 13.3 ± 0.0% in control). No effect on frequency on gene deletion was detected (ranging from 3.3 ± 0.0 to 4.2 ± 1.2% in treated vs. 2.5 ± 1.1% in control lymphocytes). We can conclude that ZnO nanoparticles in 14-days treatment do not significantly affect the level of primary DNA damage. Within 2-weeks period of treatment though significantly increased, primary lesions induced in TP53 were not reflected at the level of gene copy-number. http://dx.doi.org/10.1016/j.toxlet.2014.06.679

ZnO nanoparticles; extended-term human lymphocyte culture; comet-FISH; TP53 gene

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