April 30, 2004

Nano Weapons Join the Fight Against Cancer

Continued from page 1

By John Harney

Zhang's combination of complementary chemicals obviates the need for biopsies in diagnosis and operations in treatment and aids in early cancer detection. But according to Mauro Ferrari, a professor of biomedical engineering at Ohio State University and a specialist in biomedical applications of nanotechnology, Zhang's "work can also help us better see the anatomical contours of cancer." And according to Zhang, determining the contours of a tumor lets doctors "assess whether or not a cancer therapy is effective in humans in a matter of days rather than the current standard of three months."

Zhang's research also "gives us information on cancer molecular expression and its time evolution," Ferrari adds. A crucial problem in cancer research, he explains, is that at different stages of development the receptors of cancer cells have different molecular expression; that's why early stage cancer cells may readily uptake an effective drug; with later stage cancer cells, uptake of the drug may not be successful. Zhang's research, he says, may "help us get the right drugs to the right people at the right time."

Nanotechnology is also supplying new instruments for examining cancer, potentially yielding new insights. Adam T. Woolley, an assistant professor of chemistry and biochemistry at Brigham Young University, has created a method for examining mutations in DNA to determine a person's genetic predisposition for developing cancer. He uses a technique called atomic force microscopy (AFM), a nanoscale variation on old record players-but with a needle tip only about 10 nanometers across. Woolley first deposits DNA molecules on silicon or mica, the surfaces of which are so flat that the DNA protrudes above them. Then, he explains, he uses AFM "to examine the topography of the DNA to locate the positions of mutations in it."

"The difference in size between the native and mutated sequences of DNA is extremely small-about a tenth of a nanometer-which is at the limit of what the AFM can see," says Woolley. So he uses gold nanoparticles of about 10 nanometers to mark the mutations' positions-this way, AFM can readily see them. Examining the DNA at this level lets Woolley identify whether a double mutation occurs, which can pose a greater genetic cancer risk than a single one. Conventional techniques for looking at chromosomes can't determine such information. Woolley's work has great diagnostic potential, says Ferrari; Identifying the genetic markers for cancer might permit prevention before the first tumor cell ever forms.

Because of its practical implications for battling cancer, such research has captured the attention of the scientific community at large. Robert S. Langer, the Kenneth J. Germeshausen Professor of Chemical and Biomedical Engineering at MIT, is particularly impressed by Halas' nanoshells. "They are a very nice example of applying materials science to important medical problems," he says, "and they have a lot of exciting potential." Rick Kenyon, program manager at the breast cancer research program at the Department of Defense, is funding Halas' research because, he says, nanoshells allow for "earlier detection and earlier destruction of cancer cells-which is exactly what everybody in the cancer field is looking for."