One of the hottest areas of scientific research today is in the field of nanotechnology. Nanoparticles are frequently made of metal, and are extremely small, so small that thousands of them could fit across the width of a hair. Because metallic nanoparticles are so small, they start to act like atoms, not metals. It's this property that makes nanoparticles so interesting to scientists, who are devising many ways to use them.

One promising application is in the fight against cancer. Sally DeNardo studies cancer therapies at the University of California at Davis. She's been experimenting with iron-based nanoparticles. "We put radio-labeled antibodies that we know bind to breast cancer on the nanoparticles' surface," she explains, "and then injected them into mice in which we had implanted a very aggressive human breast cancer." The antibody-nanoparticle combinations attached themselves to the breast cancer tumor cells.

Then the researchers applied an external "alternating magnetic field" (AMF) to the area around the tumors. Denardo explains that magnetic fields cause the iron nanoparticles to become very hot. The heat then kills the breast cancer cells without harming the healthy tissue around the tumor. Denardo says researchers can control the heat. "If we give, in 20 minutes, a certain dose of the alternating magnetic field into the tumor area, we know the dose of heat we should have created on the tumor. So it can be a type of therapy that can be predicted in terms of the heat delivered."

Medical researchers have known for a long time that heat can kill cancer cells. But it's been difficult to apply heat to just the tumor cells until now. Denardo and her team have tried this therapy with hundreds of mice and had some promising results. "The tumors basically responded," she reports, "some of them going away, some of them slowing in their growth rate, and that correlated closely with the calculated heat dose."

DeNardo says she anticipates more animal studies will be conducted before this cancer treatment technique gets tried in humans. But she says her team's work shows how effective nanoparticles could be in treating disease. Her results are published in the Journal of Nuclear Medicine.