Dispersion of single-walled carbon nanotubes by a natural lung surfactant for pulmonary in vitro and in vivo toxicity studies

Background: Accumulating evidence indicate that the degree of dispersion of nanoparticles has a strong influence on their biological activities. The aims of this study were to develop a simple and rapid method of nanoparticle dispersion using a natural lung surfactant and to evaluate the effect of dispersion status of SWCNT on cytotoxicity and fibrogenicity in vitro and in vivo. Results: The natural lung surfactant Survanta (R) was used to disperse single-walled carbon nanotubes (SWCNT) in a biological medium. At physiologically relevant concentrations, Survanta (R) produced well dispersed SWCNT without causing a cytotoxic or fibrogenic effect. In vitro studies show that Survanta (R)-dispersed SWCNT (SD-SWCNT) stimulated proliferation of lung epithelial cells at low doses (0.04-0.12 mu g/ml or 0.02-0.06 mu g/cm(2) exposed surface area) but had a suppressive effect at high doses. Non-dispersed SWCNT (ND-SWCNT) did not exhibit these effects, suggesting the importance of dispersion status of SWCNT on bioactivities. Studies using cultured human lung fibroblasts show that SD-SWCNT stimulated collagen production of the cells. This result is supported by a similar observation using Acetone/sonication dispersed SWCNT (AD-SWCNT), suggesting that Survanta (R) did not mask the bioactivity of SWCNT. Likewise, in vivo studies show that both SD-SWCNT and AD-SWCNT induced lung fibrosis in mice, whereas the dispersing agent Survanta (R) alone or Survanta (R)-dispersed control ultrafine carbon black had no effect. Conclusions: The results indicate that Survanta (R) was effective in dispersing SWCNT in biological media without causing cytotoxic effects at the test concentrations used in this study. SD-SWCNT stimulated collagen production of lung fibroblasts in vitro and induced lung fibrosis in vivo. Similar results were observed with AD-SWCNT, supporting the conclusion that Survanta (R) did not mask the bioactivities of SWCNT and thus can be used as an effective dispersing agent. Since excessive collagen production is a hallmark of lung fibrosis, the results of this study suggest that the in vitro model using lung fibroblasts may be an effective and rapid screening tool for prediction of the fibrogenic potential of SWCNT in vivo.