A team of researchers from MIT, Pennsylvania State University and Carnegie Mellon University has announced key improvements to its acoustic wave-harnessing cell sorting method unveiled last year. The device, which is intended for use in the detection of cancer cells in the bloodstream, is now able to obtain accurate results from a patient sample in as little as five hours.
The pioneering method involves placing sound wave-emitting acoustic transducers either side of a microchannel. When the waves collide, they form a wave that remains at a fixed position, producing pressure nodes.
The standing waves are positioned at tilted angles along the microchannel, meaning that each cell encounters several pressure nodes during its passage. As a cell comes into contact with each node, it's pushed toward the side of the channel, with the distance of movement varying based on key factors, most notably size.
The method allows for the detection of cancer cells moving through the bloodstream, something that's traditionally difficult, with as little as 10 cancerous cells present in a 1 milliliter (0.03 fl oz) sample of a patient's blood.
A key benefit of the pioneering process is the lack of appreciable damage caused to cells during the sorting process – something that routinely occurs when using other methods, such as chemical tagging or applying mechanical force.
We first saw the technology back in August 2014, at which point it was only able to process 1-2 microliters per minute. The team didn't run a full patient sample using the earlier method, as having the blood sit in a microfluidic device for such a long period of time would have given rise to numerous complications. However, based on the processing rate, it's estimated that the earlier version would have taken 50-100 hours to sort a standard sample.
Since then, the team has worked to speed things up considerably, using data collected during testing to adjust the height and width of the channel, as well as the tilt angle of the transducers, and therefore the angle of the static sound waves used to sort the cells. Following those adjustments, it now takes around five hours to process a standard 6 milliliter (0.2 fl oz) sample, up to 20 times faster than the previous version of the method allowed.
The team put the updated version of the process to the test, sorting samples consisting of a mixture of lab-grown white blood cells and cancer cells. During the tests, the device was able to isolate 83 percent of cancer cells from samples containing as little as one cancer cell per 100,000 white blood cells.
The team also tested the improved method on blood samples obtained from three breast cancer patients, isolating one, eight and 59 tumor cells. The lowest of the results was obtained from a sample originating from a patient who was responding well to treatment, and therefore had a lower number of cancerous cells in the blood.
"With further improvement in cell throughput, this work could offer a useful new tool, for both basic research into the complex topic of circulating tumor cells and for clinical assessment of different types of cancer," said Carnegie Mellon president Subra Suresh.
With the speed improvements in mind, the method is now approaching a state viable for widespread medical use. Its ability to process samples without damaging them allows for further study of the cancerous cells following the sorting process, representing a significant advantage over existing methods.
For more on the new cell sorting technique, you can take a look at the video below
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