In vitro cytotoxicity assessment of pristine and carboxyl-functionalized MWCNTs

The wide use of carbon nanotubes (CNTs) in consumer products, i.e. composites, coatings, food packaging, etc, raise concerns about the adverse effects that CNTs can induce in humans and environment. Yet, there is no global consensus regarding risks that CNTs may pose, while controversial evidence exists also on the toxic effects associated with chemical surface modification, a prerequisite for their incorporation in different matrices. Moreover, there is limited information available about the underlying mechanisms, especially when cells' interactions with the nanomaterial is assessed by imaging techniques. The present study aims at evaluating the in vitro cytotoxicity of pristine and oxygen functionalized multi-walled CNTs (MWCNTs) by assessing cell viability and apoptosis in combination with scanning electron microscopy (SEM) observations of stabilised cells. Direct observation of adenocarcinoma human epithelial cells (A549) was performed after incubation with 12.5, 50 and 100 μg/ml MWCNTs, for 0.5, 1 and 3 h, simulating a real exposure scenario during an accident, taking into account industrial safety issues during the production and use of the nanomaterial. Functionalized MWCNTs induced higher time- and dose-dependent toxic effects as compared to pristine. The SEM observations revealed the damaging effect on the cell membrane, offering insights about the toxic mechanism that takes place.