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

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 1-40 mu g/ml of both MWCNTs for 2, 4 and 24 h. Cytotoxicity was evaluated by MTT and LDH tests and apoptosis induction, direct/oxidative DNA damage by Fpg-modified comet assay. After 24 h we found viability reduction significant at 20 and 40 mu g/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 10 mu g/ml of MWCNT-OH. A concentration-dependent increase of direct DNA damage, significant at 40 mu g/ml of MWCNTs and beginning from 5 mu g/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. (c) 2012 Elsevier Ltd. All rights reserved.