When exposed to near-infrared light, carbon nanotubes quickly release excess energy as heat. Nadine Wong Shi Kam and her colleagues at Stanford University exploited this property to attack cancerous cells. "One of the longstanding problems in medicine is how to cure cancer without harming normal body tissue," notes study co-author Hongjie Dai. Cancer cells tend to be coated in folate receptors, whereas normal cells are not. Thus, to ensure that the carbon nanotubes were attracted only to diseased cells, the researchers coated them with folate molecules. The team then shined a flashlight-size near-infrared laser on aqueous solutions of both tumor and normal cells. Although harmless to regular cells, the light heated the nanotubes to 70 degrees Celsius within two minutes, killing the cancer cells they had invaded.
The researchers hope to refine the process for future use. "Folate is just an experimental model that we used," Dai says. "In reality there are more interesting ways we can do this. For example, we can attach an antibody to a carbon nanotube to target a particular type of cancer cell." To that end, Dai is currently investigating the possibility of using the technique on mice with lymphoma because lymphoma cells have well-defined surface receptors that can be targeted.