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The objective of this study was to investigate the potential adverse health effects of occupational exposure to SWCNT dust using various in vitro approaches. Lung epithelium (represented by A549 and NHBE cells) was chosen as target cell model and exposed to minimally processed particle samples under submerse conditions and effects were compared to that of carbon black and crocidolite asbestos exposure. Cytotoxicity studies indicated low acute cytotoxicity of SWCNT. Morphological changes included decreases in microvilli and increased numbers of surfactant storing lamellar bodies and changes in cytoskeleton. Due to interactions of SWCNT and toxicity indicator dyes, the clonogenic assay was chosen as an alternative to quantify cytotoxicity and showed that long-term exposure lead to decreased cell proliferation. This effect was not only attributed to direct particle effects but also secondary SWCNT toxicity due to medium depletion. Intracellular reactive oxygen species (ROS) could only be detected in the absence of foetal bovine serum (FBS) supplements. An inflammatory mediator response was never observed. In contrast, suppression of lipid and inflammatory mediators was seen as characterised by the downregulation of interleukin-8 (IL-8) and cyclooxygenase-2 (COX-2) gene expression, inhibition of IL-8 and IL-6 promoter activation and decreased protein release of IL-8, IL-6 and macrophase chemoattractant protein-1 (MCP-1). The same response was found for cells immunologically induced by tumour-necrosis factor-a (TNF-a). Suppressive effects were partly due to TNF-a adsorption onto SWCNT surfaces. Dispersion of SWCNT in dipalmitoylphosphatidylcholine (DPPC) solution decreased particle agglomerate sizes and increased both cytotoxicity and oxidative potential.
Herzog, Eva. Toxicity assessment of single-walled carbon nanotubes. Dublin : Dublin Institute of Technology, 2009