In a natural phenomenon known as margination, platelets and leukocytes (white blood cells) within the bloodstream move towards the sides of blood vessels and adhere to them. It occurs at wound sites, during the early stages of inflammation. Recently, a team of researchers from the Massachusetts Institute of Technology and the National University of Singapore have put that process to work in a microfluidic device that could be used to cleanse the blood, perhaps acting as a treatment for bacteria-related blood disorders such as sepsis.

The device consists of a polymer chip, with a network of microchannels etched onto its surface. These channels are made using technology utilized in the manufacturing of integrated circuits, and each measure just 20 micrometers in height and width.

Initially, bacterially-infected blood flows into the device through a single channel. As it flows, the margination process causes the microbes, leukocytes, and platelets within it to move to the sides of the channel, while the red blood cells stay in the middle. Farther down the device, however, two sub-channels branch off from either side. The unwanted cells are diverted into these side channels, while the red blood cells continue following the main one. Farther down still, another two sub-channels branch off again, to remove bacteria that didn’t take one of the previous exit ramps.

A diagram illustrating how the device diverts bacteria from the red blood cells

Theoretically, the purified red blood cells could then be returned into the patient. While it might take quite a while to treat a human using a single microchannel network, the team has also tried out a larger version of the device, in which six networks run simultaneously.

In blood samples tested so far, the scientists have successfully removed 80 and 90 percent of the bacteria Escherichia coli and Saccharomyces cerevisiae, respectively. They have also been able to remove over 80 percent of the blood’s inflammatory cellular components – sepsis occurs as an inflammatory response to bacteria in the bloodstream.

MIT’s Jongyoon Han pointed out to us that the team has not actually used the device to treat sepsis ... yet. Tests on lab mice, however, are now beginning.

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