The cancer cells that circulate in many patients' bloodstreams are incredibly rare but potentially dangerous. They break off from existing tumours, travelling to new locations where they can grow into new tumours. Scientists have come up with a better way of looking for these cells — using invisible sound waves.
Existing ways to sort cancer cells out of blood are slow, and they can damage cells, rendering them useless for further tests. Sound waves, however, can gently nudge healthy and cancerous cells apart. Here's how it works, as explained by MIT's news office.
The researchers built microfluidic devices with two acoustic transducers, which produce sound waves, on either side of a microchannel. When the two waves meet, they combine to form a standing wave (a wave that remains in constant position). This wave produces pressure nodes, or lines of low pressure. Because the sound waves are tilted so they run across the microchannel at an angle, each cell encounters several pressure nodes as it flows through the channel. As cells encounter each node, they are pushed further to the side of the channel; the distance of cell movement depends on their size and other properties, such as compressibility.
The device, described in a recent issue of the journal PNAS, is 20 times faster than the prototype the team unveiled last year. The researchers used it to sort cancerous cells from the blood samples of three breast cancer patients. The key breakthrough with this technique is how it keeps the cancerous cells intact, so that they be isolated and studied in more detail. No more hiding in the haystack for these cells. [PNAS via MIT]