Applications of the comet assay in particle toxicology: air pollution and engineered nanomaterials exposure

Abstract

Exposure to ambient air particles is associated with elevated levels of DNA strand breaks (SBs) and endonuclease III, formamidopyrimidine DNA glycosylase (FPG) and oxoguanine DNA glycosylase-sensitive sites in cell cultures, animals and humans. In both animals and cell cultures, increases in SB and in oxidatively damaged DNA are seen after exposure to a range of engineered nanomaterials (ENMs), including carbon black, carbon nanotubes, fullerene C60, ZnO, silver and gold. Exposure to TiO2 has generated mixed data with regard to SB and oxidatively damaged DNA in cell cultures. Nanosilica does not seem to be associated with generation of FPG-sensitive sites in cell cultures, while large differences in SB generation between studies have been noted. Single-dose airway exposure to nanosized carbon black and multi-walled carbon nanotubes in animal models seems to be associated with elevated DNA damage levels in lung tissue in comparison to similar exposure to TiO2 and fullerene C60. Oral exposure has been associated with augmented DNA damage levels in cells of internal organs, although the doses have been typically very high. Intraveneous and intraperitoneal injection of ENMs have shown contradictory results dependent on the type of ENM and dose in each set of experiments. In conclusion, the exposure to both combustion-derived particles and ENMs is associated with increased levels of DNA damage in the comet assay. Particle size, composition and crystal structure of ENM are considered important determinants of toxicity, whereas their combined contributions to genotoxicity in the comet assay are yet to be thoroughly investigated.

Genotoxicity of TiO2nanoparticles assessed by mini-gel comet assay and micronucleus scoring with flow cytometry

“…Our results clearly showed that light exposure induced additional DNA strand breaks in anatase TiO 2 -exposed cells, with the NM100 being more effective than NM101, while rutile TiO 2 NPs showed no activity. This is thus in line with other studies (36) as well as with our previous study showing robust light-induced DNA damage for anatase TiO 2 material but not for the rutile NM103 (3). The reason for the higher activity of the NM100 is most likely due to the fact that this material is non-coated as compared to the NM101 (12).…”

Evaluating the mechanistic evidence and key data gaps in assessing the potential carcinogenicity of carbon nanotubes and nanofibers in humans

“…The alkaline comet assay has been particularly popular for studying direct genotoxicity by exposure to CNTs as well as other types of engineered nanomaterials and particulate matter from combustion-derived air pollution (Møller et al 2015a). The comet assay measures DNA migration in an agarose gel by electrophoresis at either neutral or alkaline pH.…”

Comet assay: an essential tool in toxicological research

“…Therefore, there is a strong need for more information about potential adverse health effects. One major aspect that has to be considered is the potential of NP to induce DNA damage as shown for instance for diesel and gasoline emission in traffic exhausts (DeMarini 2013) or for engineered nanomaterials (Moller et al 2015). Golbamaki et al (2015) analyzed the peer reviewed publications of the nearly last two decades and found that the method most used to evaluate the genotoxic potential of NP is the comet assay, followed by micronucleus, Ames and chromosome aberration tests.…”