Carbon nanotubes help track stem cells inside body
Researchers at Rice University have come up with a better X-ray contrast agent, which may allow for very precise tracking of cells, biomolecules, and other particles within the body. In particular, the researchers believe that seeing whether stem cells are moving towards and healing diseased tissue will be one of the first important applications for this technology. The particles consist of very short (20-80 nm) nanotubes, along with bismuth groups attached to them.
To conjugate the bismuth clusters to the carbon nanotubes, the researchers discovered that they had had to make imperfections within the nanotubes. The modified nanotubes block X-rays enormously better than iodine, the most commonly used CT contrast agent, and at least eight times better than the Rice team’s first attempt at a better contrast agent four years ago.
MRI contrast agents are currently available to track stem cells, but MRI scans are a lot more expensive and not as readily available in some areas. Moreover, in pre-clinical studies the use of X-ray radiation is not as critical, so the new contrast agent may lower the cost of stem cell and other studies that won’t have to rely on MRI any longer.
Some more details from Rice:
The compound was tested in a CT scanner at St. Luke’s Baylor Hospital, which compared the abilities of empty nanotubes, the previous generation of Bi@US-tubes and the new compound. Hounsfield units are used to measure X-ray attenuation of contrast agents. The tests found about 188 Hounsfield units for plain ultrashort nanotubes, 227 for older Bi@US-tubes and 2,178 for the latest compound. Most soft tissues fall between 30 and 100 Hounsfield units, so cells labeled with the new compound were expected to stand out.
Further testing showed the clusters hold tight to their nanotubes. The researchers detected no release of bismuth from the nanotubes tested at body temperature over 48 hours.