Comparative investigation of iron oxide nanoparticles and microparticles using the in vitro bacterial reverse mutation and in vivo Allium chromosome aberration and comet assays

Iron oxide-Fe 2 O 3 nanoparticles-NPs and microparticles-MPs widely used in medical applications were comparatively investigated for in vitro mutagenicity and in vivo cytotoxicity/genotoxicity using the Ames test in Salmonella typhimurium strains (125, 250, 500, 750, 1,000 µg/mL) and chromosome aberration/comet assays in Allium cepa (all concentrations but 1,000 µg/mL), for the first time. Neither of the particles was mutagenic in all the bacterial strains in the media without (-S9) mix. However, with the S9 mix, a significant increase was determined in the reverting colonies in some concentrations in TA 97a. In TA 102, all the concentrations but 125 µg/mL also revealed a significant increase. These effects were regarded as weak mutagens since they were < twofold of the negative value. In the Allium test, almost all concentrations of NPs and MPs significantly decreased mitotic index (MI) compared to the negative control at all treatment times (down to 6.06% at 250 µg/mL and 6.40% at 750 µg/mL at 48 h, respectively). The frequency of aberrations significantly increased following all concentrations of NPs in all treatment periods (the highest was 62.03%). However, only a few concentrations of MPs induced significant aberrations (the highest was 32.18%). In the comet assay, while the two lowest concentrations of NPs were more effective in DNA damage, Fe 2 O 3 MPs significantly increased DNA damage at more treatment points at both treatment periods. Both particles were also characterized morphologically and physicochemically . The results revealed that further investigations using different organisms and test systems are necessary for the safer usage of these particles. Graphical abstract