Will Doctors Diagnose by Listening to Your Cells?

John Roach
for National Geographic News

February 13, 2006

With the aid of a tiny device that works like the needle on the arm of a record player, a scientist has pumped up the sounds made by tiny proteins zipping around inside a yeast cell.

The discovery is driving the development of a new tool that may allow doctors to detect diseases like cancer by listening to the sounds of their patients' bodies, said James Gimzewski, a biochemistry professor at the University of California, Los Angeles.

"We already do that with the heart, which is a bunch of cells … Could we do it on the liver, the kidney, the spleen? Is there something going on there? I'm just fascinated by the whole idea," he said.

Gimzewski discovered cell sounds using a device called an atomic force microscope. But he says the name is a misnomer.

"It's not a microscope that you look through a lens to see something … [I]t's kind of a paradigm shift in a way, from looking at things to a form of feeling them," he said.

The device has a very sharp tip that is attached to a spring, like the needle on a record player.

When Gimzewski and his colleagues rested the needle on a yeast cell, they discovered the cell wall moved up and down at an audible frequency. When they fed the movement through a computer loudspeaker, they could hear it.

"It was surprising, because nobody had found [that] before," Gimzewski said.

His research team believes the sounds are produced by tiny "protein motors," proteins that can move nutrients and other materials around a cell by vibrating.

As the motors move, they cause the cell walls to shake.

Experiments

Gimzewski and his colleagues performed several experiments to determine whether cell noise was the result of protein motors or other, random movements outside the cell.

In one experiment, the team put a drop of vodka on a yeast cell. It "screamed."

"It really doesn't like it. It's probably trying to react in some way to move the alcohol out," Gimzewski said.

In another experiment, the team listened to the yeast cell at different temperatures.

"It's like a difference between a cold day and hot day," Gimzewski explained. "[Raising the temperature] doubles the frequency, doubles the pitch.

"And that is the tendency we'd expect when it's related to the metabolism of something that's very sensitive to temperature."

In a final experiment, the researchers shut off the fuel supply to the yeast cell, essentially killing it. Its response was the sound of death, a hissing sound like the white noise of a television with no reception.

The experiments convinced Gimzewski's team that the sounds of living cells are made by organized protein motors communicating with one another and moving around nutrients.

"There's a kind of cooperation between them, between the protein motors," Gimzewski said. "It's a bit like having an orchestra—all the [people playing instruments] isn't random."

Human Application

Gimzewski and colleagues first reported this discovery in August 2004 in the research journal Science.

Now the team is developing a meter to measure the movement in human cells. Their collaborator is Veeco Instruments, a Woodbury, New York-based company that makes tools for measuring at the nanoscale. (For kids: Nanomaterials)

Yeast cells are rigid enough to move the atomic force microscope's needle up and down, Gimzewski explained, but human cells are more like water balloons: too soft to move the needle.

A new device developed by the team uses a laser to record a cell's movements. The device can be moved from cell to cell with magnets.

Researchers hope that by using these meters on different parts of the body, they will be able to listen for ailments. For example, they are currently determining the sound difference between cancerous breast cells and normal breast cells.

Gimzewski says he expects cancerous cells to resonate at a lower pitch than healthy cells, because cancer cells are softer. The softness allows the cells to spread more easily through the body.

"It's a different approach to medicine, an approach in which we listen to our bodies at the cell level," he said.

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