Low Inflammatory Activation by Self‐Assembling Rosette Nanotubes in Human Calu‐3 Pulmonary Epithelial Cells

Rosette nanotubes (RNT) are a new class of metal‐free organic nanotubes synthesized through self‐assembly. Because of the wide range of potential biomedical applications associated with these materials, it is necessary to evaluate their potential in vitro toxicity. Here the cytotoxicity of a lysine‐functionalized nanotube (RNT‐K) in a human Calu‐3 pulmonary epithelial cell line is investigated. The cells were treated with media only (control), lysine (50 mg mL −1 ), RNT‐K (1, 5, and 50 µg mL −1 ), Min‐U‐Sil quartz microparticles (QM; 80 µg mL −1 ), and lipopolysaccharide (LPS; 1 µg mL −1 ). The supernatants were analyzed at 1, 6, and 24 h after treatment for the expression of three proinflammatory mediators: IL‐8, TNF‐ α and EMAP‐II. Cellular viability determined with the Trypan blue assay is significantly reduced in the QM and high‐dose RNT‐treated groups. TNF‐ α and EMAP‐II are undetectable by enzyme‐linked‐immunosorbent assay (ELISA) in the supernatant of all groups. Although IL‐8 concentrations do not differ between treatments, its concentrations increase with time within each of the groups. Quantitative reverse‐transcriptase polymerase chain reaction (qRTPCR) of IL‐8 mRNA shows increased expression in the high‐dose RNT‐treated groups at both 1 and 6 h, while an adhesion molecule, ICAM‐1 mRNA, shows the greatest increase at 6 h in the QM‐treated group. In summary, RNT‐K neither reduces cell viability at moderate doses nor does it induce a time‐dependent inflammatory response in pulmonary epithelial cells in vitro.