By Larry Greenemeier
The approach capitalizes on "tumors behaving like tumors," says von Maltzahn, a 28-year-old Ph.D. candidate, and so, triggering the growth of as many new blood vessels as quickly as possible to nourish and help them thrive. But instead of feeding these tumors, von Maltzahn relies on these ultra-porous nascent blood vessels to transport rod-shaped gold nanoparticles injected into cancer patients to the tumor, where they latch onto malignant tissue.
Although other researchers have tested the use of nanoparticles to fight cancer (read about another MIT/Harvard effort here), Von Maltzahn has developed two ways to attack tumors once the nanoparticles have set up shop there. The first is to shine a near-infrared laser on the patient's skin above the malignancies; the light heats the gold to high enough temps to interrupt and destroy cancer cells with minimal if any damage to surrounding healthy cells. In pre-clinical mouse trials a single nanoparticle injection (which includes trillions of nanoparticles) eradicated 100 percent of tumors when combined with near-infrared light. The problem with current radiation therapy is that in most cases it is not confined to malignant growths and healthy tissue gets caught in the crossfire, according to von Maltzahn.
His other award-winning technique involves two injections: the first batch are sent out as scouts to identify and attach to tumors, where they serve as markers for a second battalion of nanoparticles covered with cancer-fighting agents that home in on and destroy the tumors but ignore healthy tissue. In mouse trials, von Maltzahn and his colleagues found that this "scout-assassin" system successfully delivered doses of medicine in mice that were more than 40-times more potent and much more successful at killing tumors than were medicine-coated particles injected sans the ability to communicate with nanoparticle advance teams. The major benefit of von Maltzahn's methods is that the medication could be injected anywhere in the body but would only latch onto the cancerous tissue. "If we were injecting this directly into the tumor, it wouldn't be a transformative technology," he says. "It's essential to be able to inject it intravenously anywhere in the body and have it …. home in on the tumor." Once the medicine has been delivered, the nanoparticles would be stripped bare and could safely pass out of the body after being filtered from the blood by the spleen or liver, von Maltzahn says, noting that gold has a very low toxicity profile.
According Catherine Murphy, a chemistry professor at the University of South Carolina in Columbia, the shape of a metal determines how much light it absorbs. "If you want to shine near-infrared light, which is really good for tissue penetration, and burn something up," she says, "a rod shape works really well." Murphy developed the process for transforming spherical bits of gold into the nanorods that von Maltzahn used in his research.
Von Maltzahn, who has worked with his advisor Sangeeta Bhatia, a Harvard-MIT HST electrical engineering and computer science professor, on this research for the past five years, is co-founder of a pair of companies that he hopes will help commercialize his technique: In July 2007, he helped form Salt Lake City, Utah, -based Nanopartz Inc., a worldwide supplier of gold nanoparticles, and in September 2008, he helped create Boston-based Resonance Therapeutics, which will further develop his cancer-fighting techniques. Eugene Zubarev, an assistant chemistry professor at Rice University in Houston, developed the method for mass producing nanoparticles that Nanopartz relies on to make the nanoparticles it sells.
Von Maltzahn two years ago developed another nanotech-based approach to stopping cancer that relied on polymer-coated iron oxide nanoparticles held together by DNA tethers that together help create a visual image of a tumor through magnetic resonance imaging (MRI), as Scientific American.com reported in November, 2007. To test the particles, he and his team implanted mice with a tumor-like gel saturated with nanoparticles and placed those mice into the wells of cup-shaped electrical coils, which activated the nanoparticles via magnetic pulses.
Von Maltzahn says he's currently conducting clinical trials of his near-infrared laser technology (to ablate cancerous tumors), but it is still years away from becoming a routine treatment. The scout-assassin model is even farther from becoming a cancer-fighting staple, says Maltzahn, noting that it could take him and his colleagues another two decades to make it safe and effective enough to use in humans.
Von Maltzahn plans to keep close tabs on his companies but to continue to pursue an academic career as a professor of biomedical or chemical engineering. Neither the business nor the academic aspects of research can be overlooked if medicine is to make its way from the lab to the patient, he says. "One of the things that appeals to me," von Maltzahn says, "is developing therapeutics such as these in a way that they can be commercialized."