Induction of chromosomal aberrations by carbon nanotubes and titanium dioxide nanoparticles in human lymphocytes in vitro

We examined if three commercially available nanomaterials - short singlewall carbon nanotubes (SWCNTs), short multiwall carbon nanotubes (MWCNTs) and nanosized titanium dioxide anatase (TiO2; primary particle size <25 nm) - can induce structural chromosomal aberrations (CAs) in cultures of isolated human lymphocytes. To find a suitable sampling time, the cells were treated with 6.25-300 mu g/ml of the nanomaterials for 24, 48 and 72 h. The 48-h treatment was the most effective, inducing a dose-dependent increase in chromosome-type CAs (all materials) and chromatid-type CAs (SWCNTs and TiO2 anatase). The 72-h treatment yielded a positive result with SWCNTs. None of the treatments significantly affected cell count or the mitotic index. Our results suggest that with nanomaterials a continuous treatment for about two cell cycles is needed for CA induction, possibly reflecting access of nanomaterials to the nucleus during the first mitosis or delayed secondary genotoxic effect associated with the inflammatory process.