Microfluidic device promises cheap and fast detection of cancer cells in blood


A team of scientists from the University of Illinois at Chicago and Queensland University of Technology in Australia has demonstrated a new, cheap and fast device that can detect floating cancer cells in a tiny blood sample.

There are a variety of different methods currently being investigated in the hope of developing accurate blood tests to detect cancer. From tracking cancerous RNA traces, to detecting a unique DNA nanostructure common to almost all cancer types, we are undeniably on the cusp of an exciting new wave of diagnostics.

Perhaps one of the more straightforward prospective cancer blood tests being investigated is detecting circulating tumor cells (CTCs). These are cells that shed off the primary tumor into a person's bloodstream but the big challenge scientists have faced is producing a device that can detect these single cells, often only present in extraordinarily small quantities.

"A 7.5-milliliter tube of blood, which is a typical volume for a blood draw, might have ten cancer cells and 35-40 billion blood cells," explains Ian Papautsky, a corresponding author on the new research. "So we are really looking for a needle in a haystack."

The newly developed diagnostic device utilizes microfluidic technology to separate cancer cells from other cells in any given blood sample. Unlike other microfluidic devices that use certain biomarkers to latch onto tumor cells within a sample, often called affinity separation, the new device harnesses the theory of size-dependent inertial migration. Essentially the device filters out the CTCs based on the cells unique size compared to other elements found in a blood sample.

"Using size differences to separate cell types within a fluid is much easier than affinity separation which uses 'sticky' tags that capture the right cell type as it goes by," says Papautsky. "Affinity separation also requires a lot of advanced purification work which size separation techniques don't need."


How the device separates the tumor cells from the blood sample

The results from early testing are nothing short of remarkable. The experimental device successfully captured 93 percent of cancer cells from a 5 ml blood sample spiked with 50 CTCs. A further, even more difficult test, spiking a 5 ml sample with just 10 cells returned an 83 percent detection rate. Testing the device on blood samples from eight cancer patients, the method identified CTCs in all but two of the samples, with the researchers suggesting the error rate was simply due to only testing very small volumes of blood.

These first tests of the device looked at non-small-cell-lung-cancer CTCs but the researchers believe the system should be adaptable to a variety of other cancer types such as breast and liver cancers. As long as the CTCs are larger than blood cells the device should be broadly applicable, however the researchers do note that a minimal volume of rare CTCs can be smaller than blood cells and may be missed by the device.

The next step for the researchers is to further verify the device's efficacy in wider trials, while also improving its accuracy by adding extra biomarkers such as cancer DNA detection.