Nov. 29, 2005— A tiny sensor that can hear the subtle electrical signals naturally emitted from cells could be used one day to listen for cancer.

The so-called microelectrode cell array has the potential to not only detect tumors much earlier than current methods, but to help develop drugs that effectively kill cancerous cells.

"We literally listen to the electrical activities of the cell. We can detect if something is changing," said electrical engineer Mihri Ozkan, an assistant professor at the University of Riverside.

Ozkan is developing the device with mechanical engineer Cengiz Ozkan.

The sensor is a specially designed semiconductor chip two inches across that contains an array of electrodes, each no wider than a human hair, and a series of tiny channels used to transport fluids through the chip.

The scientists suspend a single cell above each electrode, which is sensitive enough to capture the electrical signals that occur as charged particles known as ions travel in and out of the cell's membrane during its normal function.

Healthy cells give off a unique pattern of electrical signals that the scientists record by connecting the chip to a computer.

Ozkan found that when she flooded the tiny channels in the chip with a stimulant or toxic fluid, such as a pesticide, peroxide or alcohol, and allowed it to wash over the cells, the frequency of the electrical signals changed.

That kind of biological response in the face of change could indicate a mutating or dying cell.

In the future, doctors could look for these electrical signals in tissue they suspect is cancerous but has not yet grown into a full-fledged tumor.

They could also use the technique to test whether a new cancer drug candidate is actually infiltrating a diseased cell, curing or killing it.

Current methods rely on organic dyes that stain drug molecules so that researchers can see whether the drug is working or not. But the dyes themselves can deteriorate the cell, making it unclear if the drug worked.

Whether or not cancerous cells give off electrical signals that differ from healthy cells has yet to be demonstrated, said professor Rashid Bashir, scientific director of bionanotechnology at Purdue University's Bindley Bioscience Center.

"With neurons you might see a difference in the electrical activity," he said. But with other cells, "It's not clear whether that would happen or not."

Ozkan will be trying to answer that question early next year as part of a new consortium called the Center for Cancer Nanotechnology Excellence.

Working with her colleagues at the University of San Diego, she will be analyzing healthy and cancerous breast cells for the signals that give the disease away.