Hongjie Dai from Stanford University, a member of the National Cancer Institute's Alliance for nanotechnology in cancer, found that fluorescent nanotubes can serve a dual purpose of drug delivery and imaging at the same time, to enable high precision of a drug in reaching its target cells. National Academy of Sciences published the findings of Dr. Dai and his team in its proceedings.
Single-walled carbon nanotubes were injected into a mouse by the team to watch the delivery of tubes through the bloodstream to internal organs. When the mouse was subjected to laser light, the nanotubes shone brightly responding to the laser. This image was recorded using a camera adjusted to near-infrared wavelengths of nanotubes. An anticancer drug can be attached to the nanotubes that enable the researchers to view the progression of the drug within the body of the mouse. The major advantage of nanotubes is that they fluoresce in a different range of near-infrared spectrum as compared to most dyes.
Any biological tissue naturally shines at wavelengths less than 900 nm, similar to existing biocompatible organic fluorescent dyes. This leads to unwanted background lighting which causes image smearing when dyes are injected. But, the nanotubes shine at wavelengths ranging between 1,000 and 1,400 nm Â. At these wavelengths there is negligible natural tissue fluorescence ensuring minimal background noise.
According to Dr. Dai, the nanotubes shine naturally, but they emit light in an oddball region. Many living or inert substances do not emit light in this region making it unsuitable for biological imaging. Single-walled carbon nanotubes having varied diameters and other characteristics fluoresce on adjusting the wavelength.
Upon injecting the nanotubes through the bloodstream, it was possible for the Stanford team to view the fluorescent particles traveling through the mouse’s lungs and kidneys immediately within a few seconds. After a few more seconds, the liver and spleen lit up.
Other imaging methods that can generate deep tissue images are computer tomography (CT) scans and magnetic resonance imaging (MRI), but nanotube imaging using simple machinery is used increasingly in research. Dr. Dai stated that the fluorescent nanotubes though not capable of reaching the depth of CT or MRI scans, can exhibit fluorescence beyond and near surface hence is a bright prospect for imaging systems.
Source: www.nano.cancer.gov