Functionalised thin multi-walled carbon nanotubes are less toxic to lung cells in vitro than their native...

Functionalisation of carbon nanotubes (CNTs), to make them more hydrophilic, is an essential step in their preparation for use in a wide range of industrial processes. The toxicological impact of these modifications has been investigated. However, due to the diversity of experimental models used in studies, no consensus has yet been reached. Here, we studied the toxicity of multi-walled CNT (MWCNT) with or without hydroxyl or carboxyl functional groups in lung cell models-chosen due to the risk of inhalation exposure for employees during handling of nanomaterials. In this study, we investigated the induction of the epithelial-mesenchymal transition (EMT) of human bronchial epithelial cells BEAS-2B following 6 weeks of treatment with MWCNTs ranging from 0.125 to 1 µg/cm². Epithelial and mesenchymal markers were modified following MWCNT treatment, confirming the induction of the EMT. The effect was more pronounced with non-functionalised MWCNTs than with functionalised ones. In the lung carcinoma cell line A549, IL-8 expression was measured following treatment for 24 h to 0.5-10 µg/cm² MWCNTs. An equal to or lower level was observed after treatment with functionalised MWCNTs than non-functionalised MWCNTs. Finally, the rat alveolar macrophage cell line NR8383 were exposed to 0.125-10 µg/cm² to MWCNTs for 24 h. Non-functionalised MWCNTs led to a higher proportion of binucleation than exposure to their functionalised counterparts. Functionalised MWCNTs induce toxicity in lung cell lines to a lower extent than non-functionalised MWCNTs. Because of this toxicity, all MWCNTs should be handled with care regardless of their functionalisation.