The ability to successfully isolate cancer cells is a crucial step in enabling liquid biopsy where cancer could be detected through a simple blood draw. This would eliminate the discomfort and cost of tissue biopsies that use needles or surgical procedures as part of cancer diagnosis. Liquid biopsy could also be useful in tracking the efficacy of chemotherapy over the course of time, and for detecting cancer in organs difficult to access through traditional biopsy techniques including the brain and lungs.
Isolating circulating tumor cells from the blood is no easy task since they are present in extremely small quantities. For many cancers, circulating cells are present at levels close to one per 1 billion blood cells; for example, a 7.5-milliliter tube of blood — the typical volume for a blood draw — may have 10 cancer cells and 35 to 40 billion blood cells.
Microfluidic technologies present an alternative to traditional methods of cell detection in fluids. These devices either use markers to capture targeted cells as they float by, or they take advantage of the physical properties of targeted cells — mainly size — to separate them from other cells present in fluids.
A device was developed that can isolate individual cancer cells from patient blood samples. The microfluidic device works by separating the various cell types found in blood by their size. The microfluidics chip separates cancer cells from whole blood or minimally diluted blood. While devices for detecting cancer cells circulating in the blood are becoming available, most are relatively expensive. This device is cheaper and doesn’t require a significant amount of specimen preparation or dilution.
The device capitalizes on the phenomena of inertial migration and shear-induced diffusion to separate cancer cells from blood as it passes through microchannels formed in plastic. The cells are separated based on tiny differences in size that dictate the cell’s attraction to various locations within a column of liquid as it moves. In tests, 93 percent of cancer cells was recovered using the microfluidic device.