Researchers from Massachusetts Institute of Technology (MIT), Carnegie Mellon University and Pennsylvania State University have devised a new way to separate cells by exposing them to sound waves as they flow through a tiny channel. This small device could be used to detect the extremely rare tumor cells that circulate in cancer patients’ blood. This may help doctors predict if a tumor is going to spread.
Separating cells with sound waves offers a gentler alternative to existing technologies, which require using chemicals or exposing the cells to strong mechanical forces that may damage them.
Ming Dao, a principal research scientist in MIT’s Department of Materials Science and Engineering and one of the senior authors of the paper, explained: “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.”
This technology has demonstrated can be used to separate circulating tumor cells from white blood cells.
To sort the cells using sound waves, scientists previously built microfluidic devices with two acoustic transducers which produce sound waves to both sides of the microchannel. When the two waves meet, they combine to form a standing wave (a wave that remains in a constant position). on cell size and other properties such as its compressibility. This wave produces a pressure node, or line of low pressure, running parallel to the direction of cell flow. Cells that encounter this node are pushed to the side of the channel; the distance of cell movement depends on their size and other properties such as compressibility.
For this study, the researchers first tested the system with plastic beads, finding that it could separate beads with diameters of 9.9 and 7.3 microns with about 97 percent accuracy. They also devised a computer simulation that can predict a cell’s trajectory through the channel based on its size, density, and compressibility, as well as the angle of the sound waves, allowing them to customize the device to separate different types of cells.
To test whether the device could be useful for detecting circulating tumor cells, the researchers tried to separate breast cancer cells known as MCF-7 cells from white blood cells. These two cell types differ in size (20 microns in diameter for MCF-7 and 12 microns for white blood cells), as well as density and compressibility. The device successfully recovered about 71 percent of the cancer cells; the researchers plan to test it with blood samples from cancer patients to see how well it can detect circulating tumor cells in clinical settings.
Through: MIT News
