Alumina Coating Tames Nanotube Toxicity

Coating carbon nanotubes with a layer of aluminum oxide reduces the nanomaterial’s propensity to induce pulmonary fibrosis in mice, new research shows (PLOS One 2014, DOI: 10.1371/journal.pone.0106870). Multiwalled carbon nanotubes (MWCNTs) can be long and fibrous and lodge in the lung tissue of animals when inhaled. This can cause pulmonary inflammation and fibrosis similar to that seen after exposure to asbestos. As industrial and biomedical applications for nanotubes increase, so will the potential for human exposure. Previous research has shown that attaching hydrophilic organic chains to carbon nanotubes reduces their toxicity, perhaps by breaking the tubes apart into shorter segments. James C. Bonner of North Carolina State University and colleagues have now used atomic layer deposition techniques to coat MWCNTs with Al₂O₃. Human cell cultures dosed with coated nanotubes produced lower levels of certain immune substances than the uncoated ones. The researchers also found that mice inhaling the coated nanotubes had lower rates of pulmonary fibrosis than their counterparts inhaling uncoated nanotubes. However, there were no differences in levels of pulmonary inflammation. “The aluminum oxide coating doesn’t eliminate health risks related to MWCNTs,” Bonner says, “but it does lower them.”