'Cooking' Cancer

NANOTECHNOLOGY

Carbon nanotubes can be used to kill cancer cells. Researchers at Stanford University led by chemistry professor Hongjie Dai and graduate student Nadine Wong Shi Kam have shown that carbon nanotubes can be selectively directed to cancer cells to kill them with near-infrared radiation (Proc. Natl. Acad. Sci. USA, published online, www.pnas.org/cgi/doi/10.1073/pnas.0502680102).

The nanotubes find their way to the cancer cells via folate attached to the nanotube surfaces. These cancer cells' surfaces have a large number of folate receptors, a marker for some kinds of cancer. The cells take up the nanotubes through receptor-mediated endocytosis.

When near-IR light is applied to the nanotube-penetrated cells, the nanotubes heat up as they absorb the radiation, killing the cells, Dai says. Because biological systems are transparent to near-IR radiation, only cells containing the nanotubes are harmed.

"The authors have shown a very elegant and innovative way to kill cancer cells," says Maurizio Prato, a professor in the department of pharmaceutical science at the University of Trieste, in Italy, who also studies carbon nanotubes for therapeutic uses.

The method does have potential challenges, though. Under culture conditions, the cells eventually disintegrate, and the nanotubes aggregate, "giving rise to insoluble material," Prato says. "For biological uses, covalently functionalized and fully soluble carbon nanotubes would probably be more tolerated."

Any therapeutic application is still a long way off. So far, Dai has tested the nanotubes only in cell culture. He is now collaborating with researchers at Stanford Medical School to do animal testing. They hope to learn the fate of the nanotubes after the cells die.