A Comparative Study of Different In Vitro Lung Cell Culture Systems to Assess the Most Beneficial Tool for Screening the Potential Adverse Effects of Carbon Nanotubes

To determine the potential inhalatory risk posed by carbon nanotubes (CNTs), a tier-based approach beginning with an in vitro assessment must be adopted. The purpose of this study therefore was to compare 4 commonly used in vitro systems of the human lung (human blood monocyte-derived macrophages (MDM) and monocyte-derived dendritic cells (MDDC), 16HBE14o- epithelial cells, and a sophisticated triple cell co- culture model (TCC-C)) via assessment of the biological impact of different CNTs (single-walled CNTs (SWCNTs) and multi- walled CNTs (MWCNTs)) over 24 h. No significant cytotoxicity was observed with any of the cell types tested, although a signifi- cant (p < .05), dose-dependent increase in tumor necrosis factor (TNF)-α following SWCNT and MWCNT exposure at concen- trations up to 0.02 mg/ml to MDM, MDDC, and the TCC-C was found. The concentration of TNF-α released by the MDM and MDDC was significantly higher (p < .05) than the TCC-C. Significant increases (p < .05) in interleukin (IL)-8 were also found for both 16HBE14o- epithelial cells and the TCC-C after SWCNTs and MWCNTs exposure up to 0.02 mg/ml. The TCC- C, however, elicited a significantly (p < .05) higher IL-8 release than the epithelial cells. The oxidative potential of both SWCNTs and MWCNTs (0.005-0.02 mg/ml) measured by reduced glu- tathione (GSH) content showed a significant difference (p < .05)