October 31, 2005

Drugstore Cancer Tests

A new nano-device could eventually find its way to a pharmacy aisle near you.

By Kevin Bullis

Biomedical researchers have been discovering more and more proteins that reveal the presence of a cancer before its symptoms appear -- and while its treatment success rate is still high. Yet turning these findings into quick, accurate, and inexpensive diagnostic tests has proven difficult.

Recent advances in nanotech devices, however, point to new ways for developing inexpensive and effective cancer-screening devices.

One of the most promising of these new detectors is being built by Charles Lieber, a chemist at Harvard University. In an article this month in Nature Biotechnology, he announced a highly-sensitive detector that can simultaneously find multiple cancer markers.

According to Lieber, the device, which uses nanowires to detect telltale cancer proteins, could lead to inexpensive and highly-accurate tests -- people could even buy them in a local drugstore and perform the testing themselves. "We can take a very small amount of blood and with a very simple filtration step get an answer within five minutes," Lieber says, adding that the device has "a sensitivity a thousand times better" than in a lab. 

Lieber’s prototype builds on what University of California, Berkeley chemistry professor Paul Alivisatos has called "a breakthrough series of experiments." To detect specific cancer markers, Lieber attached a monoclonal antibody specific for a certain type of protein to nanowires each about as narrow as a virus. Some earlier experiments showed that changes in the conductivity of nanowires occurs when proteins bind to an antibody. The more proteins that bind, the more the conductivity changes, revealing the concentration of the protein.

In his latest device, Lieber combined multiple nanowire detectors, each primed to be sensitive to a different cancer marker. The resulting ability to detect more than one marker is key because cancers vary. "The bottom line is no single marker, as a general rule, has had the sensitivity to be able to be used as a definitive marker," says David Sidransky, a cancer specialist at Johns Hopkins Medical Institutions.