Comparative cyto-genotoxicity assessment of functionalized and pristine multiwalled carbon nanotubes on human lung epithelial cells

► Functionalized and pristine MWCNTs induced different toxic effects in A549 cells. ► Membrane damage was detected after pristine MWCNT exposure. ► Apoptosis was induced by MWCNT-OH exposure. ► Genotoxic effects were found for both tested MWCNTs with earlier effect for MWCNT-OH. ► Functionalized and pristine MWCNT treatment did not induce oxidative DNA damage. Chemical functionalization extends CNT applications conferring them new functions, but could modify their toxicity. We compared cytotoxicity and genotoxic/oxidative effects of –OH functionalized and pristine MWCNTs to evaluated the influence of the functionalization exposing A549 cells to 1–40μg/ml of both MWCNTs for 2, 4 and 24h. Cytotoxicity was evaluated by MTT and LDH tests and apoptosis induction, direct/oxidative DNA damage by Fpg-modified comet assay. After 24h we found viability reduction significant at 20 and 40μg/ml for both the MWCNTs with a detectable viability reduction already at lower concentrations for MWCNTs. A significant LDH release was found only for MWCNTs. Significant apoptosis induction was found from 10μg/ml of MWCNT-OH. A concentration-dependent increase of direct DNA damage, significant at 40μg/ml of MWCNTs and beginning from 5μg/ml of MWCNT-OH was detected at all exposure times. Oxidative DNA damage was not observed for both CNTs. The results indicate a different cytotoxic mechanism, by membrane damage for MWCNTs and apoptosis for MWCNT-OH, that could be explained by a different cellular uptake. Moreover, we found an earlier genotoxic effect for MWCNT-OH. The findings suggest that further studies on functionalized CNTs are necessary before using them in several applications particularly in biomedical field.