Assessing the impact of the physical properties of industrially produced carbon nanotubes on their interaction with human primary macrophages in vitro

Currently it is not fully understood how carbon nanotubes (CNTs) may affect human health. Despite this, CNTs are produced at a tonne mass scale yearly. Due to their large production and intended use within a variety of applications it is imperative that a clear understanding of the hazard potential of CNTs is gained. The aim of this study therefore was to assess the impact of five different industrially produced CNTs which varied in their physical properties on the viability of human monocyte derived macrophages (MDM), and subsequently, at sub-lethal concentrations (0.005–0.02 mg/mL), their ability to cause oxidative stress and a pro-inflammatory response in these important immune cells over a 24-h period. None of the CNTs caused significant cytotoxicity up to 0.02 mg/mL after 24 h. Only the long multi-walled CNTs (MWNCTs) caused a significant, dose-dependent (0.005–0.02 mg/mL) reactive oxygen species production, whilst bundled MWCNTs showed a significant tumor necrosis factor alpha release after 24 h exposure at 0.02 mg/mL. No effects were observed for either tangled MWCNTs or short MWCNTs. It can be concluded from the findings of the present study that the industrially produced CNTs studied can cause hazardous effects in vitro that may be associated with their physical properties.