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Posted: Feb 15, 2006

Safety of carbon nanotubes can be dramatically improved

(Nanowerk News) Some concerns over the safety of nanotechnology-enabled medical therapies have been alleviated after a study has revealed an absence of toxic side effects during their use. Researchers at The School of Pharmacy, University of London modified the surfaces of carbon nanotubes to make them more compatible with the human body and biological tissues. After intravenous administration, the modified carbon nanotubes were quickly excreted intact in urine, with no retention in any organs.
The study, published in this week’s Proceedings of the National Academy of Sciences, was undertaken between multidisciplinary research groups from The School of Pharmacy, University of London, the CNRS in Strasbourg, France and the University of Trieste in Italy and was sponsored primarily by The School of Pharmacy.
Carbon nanotubes have been studied widely in recent years as potential tools of medicine. These nanoscale (one millionth of a hairs width) tubes made of carbon could be swallowed, inhaled or injected, as with many other medicines. Their novelty lies in the ability, once administered, to act like minuscule needles that can carry drugs or therapeutic genes directly into specific cells.
Previous studies by the same research group have shown that carbon nanotubes can ferry genes and drugs into mammalian cells. However, some research findings have raised concerns about the safety of carbon nanotubes. For instance, when inhaled, the tubes have been found to accumulate in lungs, causing inflammation that eventually leads to organ dysfunction.
The current study, led by Dr Kostas Kostarelos from The School of Pharmacy, in collaboration with Dr Alberto Bianco (France) and Professor Maurizio Prato (Italy), provides the first indication that once carbon nanotubes have been appropriately adapted – through surface chemical modifications – their safety is dramatically improved. The researchers traced the transit of intravenously administered carbon nanotubes through the bloodstream using the technique of gamma scintigraphy. They found that whilst the modified carbon nanotubes were detected in organs soon after administration, the tubes were quickly eliminated from the organs. Moreover, urine excretion analysis revealed that the nanotubes were eventually eliminated intact. These results indicating the safety of modified carbon nanotubes provide great promise for their further development as medical tools.
"The field of nanotechnology has been struggling in the last few years to demonstrate that carbon nanotubes can be made safe, which would allow for their beneficial use in a variety of applications," said Dr Kostarelos, lead author of the study and Deputy Director of the Centre for Drug Delivery Research at The School of Pharmacy.
"We hope that our results will provide hope in the search for a new generation of safe and effective medical therapies. The next stage of our work will be to investigate ways of controlling the length of time that these nanotubes remain in the body, to allow them to carry out their work before they are excreted."
Source: University of London