Comparing in vitro cytotoxicity of graphite, short multi-walled carbon nanotubes, and long multi-walled carbon nanotubes.

Occupational and environmental exposures to carbon-based materials in nano- and micro-size have been reported. There is incomplete information on the impact of size on the toxicity of carbon-based materials. The objective of this study is to compare the toxicity of graphite, short multi-walled carbon nanotubes (S-MWCNTs), and long multi-walled carbon nanotubes (L-MWCNTs) in lung cells (A 549). The physicochemical properties of MWCNTs were determined using analytical instruments. The fibers of MWCNTs were dispersed in the sterile-filtered 0.05% bovine serum albumin in MilliQ water. Cytotoxicity of graphite and MWCNTs were assessed using the cell viability, reactive oxygen species (ROS), and lipid peroxidation experiments. Results showed that MWCNTs induced cytotoxicity through the generation of oxidative stress in the exposed lung cells. Mean cytotoxicity of S-MWCNTs was statistically more than that of L-MWCNTs. The graphite induced cytotoxicity only at high concentrations. The mean cytotoxicity of both S-MWCNTs and L-MWCNTs was statistically more than that of graphite. The results also indicated that oxidative stress was the probable toxicity mechanism of carbon-based materials. The decreasing size of carbon-based materials could increase their toxicity. Because of the toxicity of MWCNTs, it is imperative to consider health and safety issues in working with nanomaterials.