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

Abstract

<p>Abstract</p> <p>Background</p> <p>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 <it>in vitro </it>and <it>in vivo</it>.</p> <p>Results</p> <p>The natural lung surfactant Survanta^®was used to disperse single-walled carbon nanotubes (SWCNT) in a biological medium. At physiologically relevant concentrations, Survanta^®produced well dispersed SWCNT without causing a cytotoxic or fibrogenic effect. <it>In vitro </it>studies show that Survanta^®-dispersed SWCNT (SD-SWCNT) stimulated proliferation of lung epithelial cells at low doses (0.04-0.12 μg/ml or 0.02-0.06 μg/cm²exposed 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^®did not mask the bioactivity of SWCNT. Likewise, <it>in vivo </it>studies show that both SD-SWCNT and AD-SWCNT induced lung fibrosis in mice, whereas the dispersing agent Survanta^®alone or Survanta^®-dispersed control ultrafine carbon black had no effect.</p> <p>Conclusions</p> <p>The results indicate that Survanta^®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 <it>in vitro </it>and induced lung fibrosis <it>in vivo</it>. Similar results were observed with AD-SWCNT, supporting the conclusion that Survanta^®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 <it>in vitro </it>model using lung fibroblasts may be an effective and rapid screening tool for prediction of the fibrogenic potential of SWCNT <it>in vivo</it>.</p