In the first experiments of their kind, researchers 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.
These findings are from the first in vivo animal study of polymer-coated carbon nanotubes, a nanomaterial that researchers hope will prove useful in diagnosing and treating disease.
"We sampled tissues from a dozen organs, and found significant amounts of nanotubes only in the liver," said team leader Bruce Weisman, Ph.D., of Rice University. "The liver naturally removes drugs or compounds from the blood, so this is what we expected to find."
The study, which was published in the Proceedings of the National Academy of Sciences USA, tracked where the nanotubes went within 24 hours of being injected. The investigators were able to follow the nanotubes thanks to the intrinsic near-infrared fluorescence of the nanotubes. These studies 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.
"The early results are promising for anyone interested in using carbon nanotubes in biomedical applications," said Steven Curley, M.D., whose group at the University of Texas M.D. Anderson Cancer Center collaborated with Weisman’s research group. "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."
In the current study, Weisman, Curley, and colleagues injected lab animals with single-walled carbon nanotubes that were coated with a polymer designed to make the nanotubes soluble in water. The nanotubes, whose biocompatible coating was displaced within seconds by proteins in the blood, continued to fluoresce in the animals. The animals showed no ill effects from receiving nanoparticle injections.
This work, which was supported in part by the National Cancer Institute, is detailed in a paper titled, “Mammalian pharmacokinetics of carbon nanotubes using intrinsic near-infrared fluorescence.” This paper is available at no charge through PubMed Central. View paper.
Posted 19th December 2006