Balaji Panchapakesan likes to leave innocuous packages lying around, then detonate them remotely, killing any victims who are near the blast. No, he's not an Iraqi insurgent – he's an engineering professor at the University of Delaware, and his bombs are carbon nanotubes. His explosions are on the nanoscale, and his victims are cancer cells. His idea that nanobombs can fight cancer in a cell-by-cell war of attrition has been effective in petri dishes.
At the heart of Panchapakesan's nanobombs are single-walled carbon nanotubes. While these tiny structures have been heralded as the material of the future for their astounding strength, Panchapakesan is focused on one of their other strange features: When heated by a laser at an 800-nanometer wavelength, they explode.
Video
Watch microscopic footage of a sheet of carbon nanotubes exploding after being exposed to laser light.
Credit: Balaji Panchapakesan & Shoaxin Lu
The exact physics of the combustion aren't well understood, but it probably works because water molecules stuck inside spaghetti-like globs of the nanotubes overheat and force the explosion to occur. Since the explosive nature of nanotubes was first discovered in 2002, some scientists have theorized that they could form a new kind of military explosive or even a rocket propellant.
Panchapakesan saw another possibility. Why not sprinkle them next to cancer cells and then blow them up like tiny improvised explosive devices? He did just that, and the method showed enormous selectivity when he focused the laser on the cells he wanted to excise.
"In other words, we can reduce the collateral damage so that we're killing only the cells we want to kill without harming healthy cells," he says.
While the explosive aspect of his research is novel, Panchapakesan isn't the first to use nanodevices to fight cancer. Naomi Halas, a Rice University engineering and chemistry professor, showed in 2003 that she could kill cancer cells by inserting nanoshells made of gold and heating them with near infrared light to the point where they die. Stanford's Hongjie Dai (.pdf) performed a similar feat with carbon nanotubes this year.
Halas has since used her gold nanoshells to induce a complete remission in mice with colon-cancer tumors, without any recurrence of the cancer in their natural lifetimes. She cautions that Panchapakesan's concept is at the very early stages, and a mountain of evidence is needed to show it would be safe and effective in humans.
"For it to work as a therapy, it has to be a highly controlled, highly regular bio-compatible structure," Halas says.
Panchapakesan agrees that he's in the very early stages of his research, but he sees even more potential as the carbon nanotubes become cheaper to manufacture and easier to manipulate. "Eventually we might be able to create a cage which brings a toxic molecule to a cancer cell and then, upon release, the cage itself explodes, making (a) two-tiered attack on the cancer cell."
But that's for future research projects. For right now, he's content just to blow his enemy to bits.
