Nanotubes pass in vivo test

Individual, chemically unmodified single-walled carbon nanotubes (SWNTs) have passed the first in vivo test of their pharmacokinetics in a mammal (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.0609265103). Scientists envision using nanotubes as chemotherapeutic agents, as contrast agents for diagnostic imaging, and in other biomedical applications. But first, they have to understand the behavior and fate of these foreign nano-objects inside the body. The initial results appear promising. Rice University chemist R. Bruce Weisman and his colleagues intravenously administered surfactant-coated SWNTs to rabbits and were able to track the tubes by observing their characteristic near-infrared fluorescence. The team found that blood proteins quickly displaced the surfactant coating on the nanotubes and that the tubes' concentration in blood serum fell exponentially, with a half-life of one hour. After 24 hours, significant levels of nanotubes were found only in the liver, as expected. The absence of acute toxicity and promising persistence of the nanotubes in circulation suggest they may have a future in pharmaceutical applications, the researchers say.