Research from Stanford University has shown that carbon nanotubes loaded with anticancer drugs can target tumor cells while steering clear of healthy tissue.
The nanotubes--on average 100 nanometers long and a few nanometers wide--pass easily through the leaky walls of tumor blood vessels but do not get into healthy blood vessels. So the researchers realized that drugs attached to the nanotubes could be carried inside tumors without harming normal tissue.
To make working nano-drug transporters, the researchers coated the nanotubes with a molecule called polyethylene glycol (PEG), which has three branches on one end, then attached molecules of the anticancer drug paclitaxel to each branch. Each of the 100-nanometer-long nanotubes carried about 150 drug molecules in total. "Think of a carbon nanotube as a boat," says Steve Lippard, a chemistry professor at MIT, who was not involved in the research. "The advantage of the branched PEG is that you can have multiple passengers at each seat." Dai adds that the branched PEG is stable in the bloodstream for a relatively long time, giving the nanotubes more time to find and treat a tumor before leaving the body.
The drug-delivery technique was tested in mice that had been injected with breast cancer cells. Once the tumors grew to a specific size, the researchers administered a dose of the drug-laden nanotubes every six days. They gave another group of mice similar doses of different forms of paclitaxel, including the clinical drug Taxol, and left some untreated. After 22 days, they found that the tumors treated by nanotube delivery were less than half the size of the tumors treated by the second most effective treatment, Taxol.
Friday, August 29, 2008
MIT Technology Review reports that carbon nanotubes could reduce the side effects of cancer drugs and mice tests show they are twice as effective at reducing tumor size. The researchers estimate that drug uptake within a tumor was 10 times higher for nanotube delivery than for Taxol. This uptake means that smaller doses could be used to achieve the same effects as other treatments, reducing side effects.