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Chemical Treatments Can Reduce Carbon Nanotube Toxicity

Carbon nanotube illustration (National Science Foundation)

Carbon nanotube illustration (National Science Foundation)

Researchers at University College London, with colleagues in the U.K., France, Italy, and Spain found ways to reduce the toxicity of carbon nanotubes, which are structurally similar to asbestos. The findings of the team led by UCL chemical engineer and pharmacy professor Kostas Kostarelos appear online in the journal Angewandte Chemie (paid subscription required).

Carbon nanotubes are sheets of carbon atoms formed into tubes just a few nanometers in diameter — 1 nanometer equals 1 billionth of a meter — and are considered essential for advanced manufactured materials, hydrogen fuel cells, and some medical therapies. For example, carbon nanotubes can be engineered to pierce cell walls to deliver diagnostic agents or drugs directly into cells.

The shape and size of carbon nanotubes, however, are similar to highly toxic asbestos fibers, and some research indicates cells of lab animals react to carbon nanotubes much like asbestos. A key factor in making carbon nanotubes toxic, says Kostarelos, is their length. Reducing the length of the nanotubes can reduce their toxicity. But shortening the tubes is not enough; carbon nanotubes also must also be able to stay suspended in biological fluids without aggregating.

Kostarelos and colleagues tested possible ways of treating carbon nanotubes to reduce their length and make them less toxic.  The researchers report treatment with triethylene glycol (TEG), a chemical used in fragrances for cosmetics, pesticides, plastics, and printing inks, is one means of producing less toxic nanotubes. TEG has shown to be a mild skin and eye irritant in animal studies, but has no other listed effects from short-term or long-term exposure.

“What we show for the first time is that in order to design risk-free carbon nanotubes both chemical treatment and shortening are needed,” notes Kostarelos. “Creative strategies to identify the characteristics that nanoparticles should possess in order to be rendered ‘safe-for-use’,” he adds, “and the ways to achieve that, are essential as nanotechnology and its tools are maturing into applications and becoming part of our everyday lives.”

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