New nanotube findings by Stanford researchers give boost to potential biomedical ap...( Carbon nanotubes-cylinders so tiny t...),Health

Carbon nanotubes-cylinders so tiny that it takes 50,000 lying side by side to equal the width of a human hair-are packed with the potential to be highly accurate vehicles for administering medicines and other therapeutic agents to patients. But a dearth of data about what happens to the tubes after they discharge their medical payloads has been a major stumbling block to progress.

Now, Stanford researchers, who spent months tracking the tiny tubes inside mice, have found some answers.

Studies in mice already had shown that most nanomaterials tend to accumulate in organs such as the liver and spleen, which was a concern because no one knew how long they could linger. But fears that the tiny tubes might be piling up in vital organs, like discarded refrigerators at the bottom of a rural ravine, can now be put to rest, said Hongjie Dai, the J. G. Jackson and C. J. Wood Professor of Chemistry at Stanford, whose research team has demonstrated that the nanotubes exit the organs.

Dai and his group found that the carbon nanotubes leave the body primarily through the feces, with some by way of the urine. ''That's nice to know,'' Dai said. ''This now proves that they do get out of the system.''

The full extent of the news, which is scheduled to be published the week of Jan. 28 in Proceedings of the National Academy of Sciences Online Early Edition (PNAS), is even better than that: The three-month-long study also allays worries that the nanotubes, by simply remaining in the organs for a long time, would prove toxic to the mouse.

''None of the mice died or showed any anomaly in the blood chemistry or in the main organs,'' said Dai, senior author on the PNAS paper. ''They appear very healthy, and they are gaining weight, just like normal mice. There's no obvious toxicity observed.'' The lack of toxicity of nanotubes in mice is consistent with a previous pilot study done by Sanjiv Gambhir, a professor of radiology at Stanford, and
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