Sound waves separate tumor and blood cells

Date: Aug-28-2014 A tool that can test a cancer patient's blood for rare tumor cells is extremely useful

for checking if a tumor is going to spread. Now scientists have found a way to do

this using "tilted" sound waves in a device no bigger than a small coin, offering an effective

way of sorting cells without having to treat them with chemicals or deform them

mechanically.

The team includes members from MIT (Cambridge, MA), Pennsylvania State University (University Park, PA), and Carnegie Mellon

University (Pittsburgh, PA), and reports its findings in the Proceedings of the National Academy of

Sciences.

Sound waves offer a way to sort cells without having to expose them to chemicals or damaging

forces, as co-senior author of the new study, Dr. Ming Dao, a principal research scientist in

MIT's Department of Materials Science and Engineering, explains:

"Acoustic pressure is very mild and much smaller in terms of forces and disturbance to the

cell. This is a most gentle way to separate cells, and there's no artificial labeling

necessary."

Tilted sound waves separate cell types more effectively

Theirs is not the first attempt to separate cells and small particles using sound waves. If

you take a mixture of cells or particles and make them flow in one direction, you can deflect

their travel very slightly by exposing them to sound waves. The amount of deflection depends on

the cells' physical properties like size and compressibility.

Sound waves offer a way to sort cells without having to expose them to chemicals or damaging forces.

Illustration: Christine Daniloff/MIT

But previous efforts to make cell separators work using sound waves have not been able to

make the difference in deflection big enough to separate the cells effectively.

Dr. Ming and colleagues solved the problem by using tilted sound waves. These cross the

cells' trajectory at an angle instead of going straight across, ensuring that each cell

encounters several low-pressure nodes on its journey through the microchannel instead of just

one.

In their study, the team first tested their device using plastic beads and showed it could

separate beads of 9.9 microns from beads of 7.3 microns in diameter with around 97% accuracy. A

micron is one thousandth of a millimeter.

They further developed the device by adding a computer simulation module that can predict the

trajectory of a particle through the microchannel based on its size, compressibility and density

and the angle of the sound waves. This feature means the device can be customized to sort

different types of particle or cell.

71% of tumor cells recovered in a lab mix of breast cancer and white blood cells

The team also tested how well the device was able to separate MCF-7 breast cancer cells (20

microns diameter) from white blood cells (12 microns in diameter). The cells also differ by

compressibility and density.

The results showed the cell sorter recovered around 71% of the cancer cells.

The team now plans to test the device with blood samples from cancer patients in clinical

settings. Circulating tumor cells are very rare - one milliliter of a typical cancer patient's

blood may only contain a few tumor cells.

The researchers have filed for a patent on their device. They see it helping clinicians

determine whether a patient's tumor is about to spread to other sites of the body. When tumors

are readying to do this, they begin to send out cells that travel through the bloodstream.

The National Institutes of Health and the National Science Foundation helped fund the

study.

You can view the device in action by playing the video below.

Meanwhile, Medical News Today recently learned how engineers at Princeton

University, NJ, are working on a way to use laser technology to measure blood glucose non-invasively. They hope one day their innovative diagnostic method will help diabetics do away with pin pricks for testing

blood sugar.

Written by Catharine Paddock PhD

View all articles written by Catharine, or follow her on:

Courtesy: Medical News Today Note: Any medical information available in this news section is not intended as a substitute for informed medical advice and you should not take any action before consulting with a health care professional.