Nanoparticles are a cause for concern because of their potential toxic effects on human health and the environment. The aim of this study was to assess the toxic effect of chitosan-coated magnetite nanoparticles (11.00±4.7 nm) on Drosophila melanogaster through the observation of hemolymph composition, DNA damage, larval survival and lifespan of flies. Chitosan-coated magnetite nanoparticles were synthesized by coprecipitation method. Drosophila larvaes and adults were exposed to 500 and 1000

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... m nanoparticles solution. After exposure, each type of larval hemocytes was recognized. Comet assay was performed to detect the DNA damage in the hemocytes. Also, the larval survival and lifespan of exposed flies were observed. Our results showed the toxic effect of the chitosan-coated magnetite nanoparticles through the increment of hemocytes, the emergence of lamellocytes, the presence of apoptotic hemocytes and the DNA damage detected by comet assay. In addition, nanoparticles produce decreasing of larval survival and shortening of the mean and maximum lifespan. The toxic effect the chitosan-coated magnetite nanoparticles is directly associated with 1000 ppm. No DNA damage was observed at 500 ppm.