Comparative Assessment of Genotoxic Impacts Induced by Zinc Bulk- and Nano-Particles in Nile tilapia, Oreochromis niloticus.

Fish were separately exposed to 1/2 LC50/96 h values of bulk-Zn and nano-Zn for 7, 14, and 28 days. The induction of micronuclei (MN) and other eight nuclear abnormalities in erythrocytes showed marked time and size dependence. The frequencies of all nuclear anomalies were progressively elevated (p < 0.05) with increasing the time of exposure to both bulk-Zn and nano-Zn. Throughout the study periods, fish exposed to nano-Zn showed the maximum elevation in all studied nuclear anomalies. Based on the fragmented DNA values, both Zn forms induced tissue-specific DNA damage as following gills > liver > muscles. Moreover, nano-Zn exposed groups revealed a maximum percentage of DNA damage among all studied groups, especially after 14 days. The percentage of DNA damage was decreased in all tissues on the 28th day, which reflected the presence of an effective repair mechanism. Finally, nano-Zn exhibited more genotoxic effects than that of its bulk counterparts.