"One of the longstanding problems in medicine is how to cure cancer without harming normal body tissue," says Hongjie Dai, an associate professor of chemistry at Stanford and co-author of the study. "Standard chemotherapy destroys cancer cells and normal cells alike. That's why patients often lose their hair and suffer numerous other side effects. For us, the Holy Grail would be finding a way to selectively kill cancer cells and not damage healthy ones."
For the PNAS experiment, Dai and his colleagues used a basic tool of nanotechnology--carbon nanotubes, synthetic rods that are only half the width of a DNA molecule. Thousands of nanotubes could easily fit inside a typical cell.
"An interesting property of carbon nanotubes is that they absorb near-infrared light waves, which are slightly longer than visible rays of light and pass harmlessly through our cells," Dai says. But shine a beam of near-infrared light on a carbon nanotube, and the results are dramatic. Electrons in the nanotube become excited and begin releasing excess energy in the form of heat.
In the experiment, Stanford researchers found that if they placed a solution of carbon nanotubes under a near-infrared laser beam, the solution would heat up to about 158 degrees F (70 C) in two minutes. When nanotubes were placed inside cells and radiated by the laser beam, the cells were quickly destroyed by the heat. However, cells without nanotubes showed no effects when placed under near-infrared light.
"It's actually quite simple and amazing," Dai observes. "We're using an intrinsic property of nanotubes to develop a weapon that kills cancer."