13 Functionalised thin MWCNTs are less toxic on lung cell lines than their native counterparts

Abstract In order to extend the range of applications and uses of carbon nanotubes (CNT), many have been functionalised. However, due to the diversity of experimental models used in studies, it remains difficult to conclude whether functionalised CNTs are more, less or equally toxic than their native counterparts. In this study, we selected thin multi-walled CNTs (MWCNTs) with hydroxyl or carboxyl functional groups. We studied the toxicity of these MWCNTs on three lung cell lines since the main route of occupational exposure is inhalation. First, bronchial epithelial BEAS-2B cells were used to study the epithelial-mesenchymal transition (EMT). After 6 wk of culture, during which the cells were treated with MWCNTs twice a week, induction of EMT was more pronounced with pristine MWCNTs than with functionalised ones. Secondly, the expression of the cytokine IL-8 in A549 cells was assessed after 24 h of treatment. This cytokine expression was similar or lower after treatment with functionalised MWCNTs than with pristine particles. Finally, analysis of alveolar macrophages NR8383 treated for 24 h showed an increase in the percentage of binucleated cells, an effect that was more marked with pristine MWCNTs than with functionalised CNTs. This study showed that thin MWCNTs have an impact in lung cells: induction of EMT involved in lung diseases, increased expression of IL-8, which can predict lung inflammation, and impaired integrity of macrophages, which constitute the lung’s first line of defence. Although the effects are less pronounced with functionalised MWCNTs than with their pristine counterparts, they still induce adverse effects on lung cells and must be handled with caution.