The nanotubes usefulness is further boosted because tissue scatters less light in the longer wavelength region of the near-infrared, reducing image smearing as light moves or travels through the body, another advantage over fluorophores emitting below 900nm.
"The nanotubes fluoresce naturally, but they emit in a very oddball region," Dai said. "There are not many things living or inert that emit in this region, which is why it has not been explored very much for biological imaging."
By selecting single-walled carbon nanotubes (SWNTS) with different chiralities diameters and other properties, Dai and his team can fine-tune the wavelength at which the nanotubes fluoresce.
The nanotubes are imaged immediately upon injection into the bloodstream of mice.
Dai and graduate students Sarah Sherlock and Kevin Welsher, who are also coauthors of the PNAS paper, observed the fluorescent nanotubes passing through the lungs and kidneys within seconds after injection. The spleen and liver lit up a few seconds later.
The group also did some "post-production" work on digital video footage of the circulating nanotubes to further enhance the image quality using a process called "principal component analysis."
"In the raw imaging, the spleen, pancreas and kidney might appear as one generalized signal," Sherlock said. "But this process picks up the subtleties in signal variation and resolves what at first appears to be one signal into the distinct organs."
"You can really see things that are deep inside or
|Contact: Louis Bergeron|