Dispersing Nanotubes Renders Them Nontoxic

Because of their extremely large aspect ratio—the ratio of length to diameter—single-walled carbon nanotubes have been likened to asbestos in their ability to infiltrate and irritate the lungs. But researchers at Northwestern University contend that the comparison is incorrect. SWNT pulmonary toxicity, they say, arises from aggregates of the nanomaterial, not individual tubes (Nano Lett., DOI: 10.1021/nl9042483). SWNTs tend to exhibit their desirable physical properties when dispersed, so a team led by G. R. Scott Budinger, Mark C. Hersam, and Gökhan M. Mutlu decided to compare the toxicity of nanotube aggregates with that of nanotubes dispersed in the biocompatible block copolymer Pluronic F 108NF. They found that mice exposed to aggregates of the nanomaterial developed an inflammatory reaction leading to mild fibrosis in the large airway after 30 days. In mice treated with dispersed SWNTs, however, macrophages gradually cleared the material, and no toxicity was observed. This method of biocompatible dispersion should allow SWNTs “to be safely stored, handled, and transported for use in commercial or biomedical applications,” the researchers note.