An in vitro study of the potential of carbon nanotubes and nanofibres to induce inflammatory mediators and frustrated phagocytosis

There has been little information to date based on the potential health effects and hazards associated with the inhalation of carbon nanofibrous materials by workers despite their growing use in industry. This study examines the in vitro effects of a range of nanofibres and nanotubes for their ability to stimulate the release of the pro-inflammatory cytokine TNF-α and reactive oxygen species (ROS) from monocytic cells. Also assessed were the toxic effect of the nanomaterials on the cells and the phagocytic ability of the cells after exposure. Our studies showed that the cellular response varied with fibre morphology and state of aggregation; long, straight, well-dispersed nanofilaments produced significantly more TNF-α and ROS in monocytic cells compared with highly curved and entangled materials. We also demonstrated that monocytic cell phagocytic ability was reduced after exposure to all of the nanotubes used in this study. Microscopic examination of the cells after treatment with the nanotubes showed ‘frustrated phagocytosis’, The frustrated phagocytosis suggests that clearance of nanotubes from the lungs by macrophages may be impaired. There was no evidence of a toxic effect at any of the doses or time points used. These considerations may have important consequences for workers exposed to these nanomaterials.