Picosound Ultrasonics Able to Probe Cells Non-invasively

Scientists from the University of Bordeaux in France used high-frequency sound waves to test the stiffness and viscosity of the nuclei of individual and living human cells. The approach could prove to be helpful in answering questions such as how cells adhere to medical implants and why healthy cells turn cancerous.

"We have developed a new non-contact, non-invasive tool to measure the mechanical properties of cells at the sub-cell scale," says Bertrand Audoin, a professor in the mechanics laboratory at the University of Bordeaux. "This can be useful to follow cell activity or identify cell disease."

The technique, called picosecond ultrasonics, is already known and tested but for a very different purpose, namely to measure the thickness of semiconductor chip layers.

The researchers grew cells on a metal plate and then flashed the cell-metal interface with an ultra-short laser pulse to generate high-frequency sound waves. Another laser measured how the sound pulse propagated through the cells, giving the scientists clues about the mechanical properties of the individual cell components.

"The higher the frequency of sound you create, the smaller the wavelength, which means the smaller the objects you can probe" says Audoin. "We use gigahertz waves, so we can probe objects on the order of a hundred nanometers." To put this into perspective, a cell's nucleus is about 10,000 nanometers wide.

The team now plans to study cancer cells with sound in the coming years. "A cancerous tissue is stiffer than a healthy tissue," notes Audoin. "If you can measure the rigidity of the cells while you provide different drugs, you can test if you are able to stop the cancer at the cell scale."