HOUSTON, Nov. 27, 2006 -- In the first experiments of their kind, researchers at Rice University and The University of Texas M. D. Anderson Cancer Center have determined that carbon nanotubes injected directly into the bloodstream of research lab animals cause no immediate adverse health effects and circulate for more than one hour before they are removed by the liver.

The findings are from the first in vivo animal study of chemically unmodified carbon nanotubes, a revolutionary nanomaterial that many researchers hope will prove useful in diagnosing and treating disease. The research will appear in this week's online edition of the Proceedings of the National Academy of Sciences.

"We sampled tissues from a dozen organs, and found significant amounts of nanotubes only in the liver," said lead author Bruce Weisman, professor of chemistry. "The liver naturally removes drugs or compounds from the blood, so this is what we expected to find."

The study, which tracked where the nanotubes went within 24 hours of being injected, also revealed trace amounts of nanotubes in the kidneys another common expulsion route for drugs. There was no evidence that nanotubes remained in other tissues in the body.

Nanotubes are hollow cylinders of pure carbon that measure just one nanometer in diameter about the same width as a strand of DNA. Nanotubes have unique chemical and optical properties, and they have attracted intense interest from biomedical researchers.

"The early results are promising for anyone interested in using carbon nanotubes in biomedical applications," said co-author Dr. Steven Curley, professor of surgical oncology and chief of gastrointestinal tumor surgery at M. D. Anderson. "We are particularly pleased that the fluorescent effect remains intact in our application, because this makes it easier to see where the nanotubes end up, and it opens the door to some exciting diagnostic and therapeutic applications."