Fluorescent nanotubes

Mice are a common model organism for studying disease and treatments. However, it’s not always easy to see just what’s going on inside the mice. Hongjie Dai, Kevin Welsher and Sarah Sherlock of Stanford University have successfully used fluorescing carbon nanotubes to peer inside living mice.

Although biological fluorescent dyes have been used for a long time, they generally aren’t useful beyond a few millimeters. That’s partly because the animal tissues fluoresce at the same wavelengths as the dyes (below 900 nanometers). In contrast, Dai’s biocompatible single-walled carbon nanotubes (SWNTs) fluoresce between 1000 and 1400 nanometers. At these longer wavelengths, not only is there little background contamination, but also less scattering of the light, leading to sharper images. In addition, the SWNTs are visible not millimeters but centimeters deep within tissue. Considering that a mouse’s body is only centimeters deep, that’s quite an advantage.

Dai and his team were able to observe the journey of the SWNTs through the bloodstreams and ultimately into the various organs of living mice.

Caption: An enhanced color image of fluorescence from single-walled carbon nanotubes (right) shows internal organs of a mouse next to a reference illustration (left). In the fluorescent image, on the left side of the mouse, the pancreas (thin green strip) is sandwiched between a kidney (yellow) and the spleen (pink). In the reference image, the kidneys are orange-brown, the spleen is pumpkin-colored and the pancreas is barely visible as a tiny red triangle between the other two organs.

Credit: reproduced with permission from Proceedings of the National Academy of Sciences USA.