Cytotoxicity and genotoxicity of panel of single- and multi-walled carbon nanotubes: in vitro effects on normal Syrian Hamster Embryo (SHE) and immortalized V79 hamster lung cells

Carbon nanotubes (CNTs) belong to a very specific class of nanomaterials with unique properties. Because of their anticipated use in a wide range of industrial applications, their toxicity is of increasing concern.
In order to determine whether specific physico-chemical characteristics of CNTs are responsible for their toxicological effects, we investigated the cytotoxic and genotoxic effects of eight CNTs representative of each of the commonly encountered classes (single-, double- and multi-walled CNTs; purified and raw). In addition, because most previous studies of CNT toxicity were conducted on immortalized cell lines, we decided to compare results obtained from V79 cells, an established and well-known cell line, with results from SHE (Syrian Hamster Embryo) cells, an easy-to-handle normal cell model which also has the advantage of being a non-transformed/modified cell model.
After 24 hours of treatment, multi-walled carbon nanotubes were generally found to be more cytotoxic than single- or double-walled CNTs. Multi-walled CNTs also provoked more genotoxic effects, as revealed by micronucleus assays in both cell types and by the comet assay in SHE cells. No correlation could be found between CNT genotoxicity and metal impurities, length, surface area, or induction of cellular oxidative stress, but genotoxicity was seen to increase with CNT width. The cytotoxicity and genotoxicity observed for some CNTs lead us to suggest that they might also act by interfering with the cell cycle, but no significant differences were observed between normal and immortalized cells.