Microfluidic Device Filters Blood

Microfluidic Device Filters Blood

Sepsis is an adverse systemic inflammatory response caused by microbial infection in blood. This paper reports a simple microfluidic approach for intrinsic, non-specific removal of both microbes and inflammatory cellular components (platelets and leukocytes) from whole blood, inspired by the invivo phenomenon of leukocyte margination. As blood flows through a narrow microchannel (20 × 20 µm), deformable red blood cells (RBCs) migrate axially to the channel centre, resulting in margination of other cell types (bacteria, platelets, and leukocytes) towards the channel sides. By using a simple cascaded channel design, the blood samples undergo a 2-stage bacteria removal in a single pass through the device, thereby allowing higher bacterial removal efficiency. As an application for sepsis treatment, we demonstrated separation of Escherichia coli and Saccharomyces cerevisiae spiked into whole blood, achieving high removal efficiencies of ?80% and ?90%, respectively. Inflammatory cellular components were also depleted by >80% in the filtered blood samples which could help to modulate the host inflammatory response and potentially serve as a blood cleansing method for sepsis treatment. The developed technique offers significant advantages including high throughput (?1 ml/h per channel) and label-free separation which allows non-specific removal of any blood-borne pathogens (bacteria and fungi). The continuous processing and collection mode could potentially enable the return of filtered blood back to the patient directly, similar to a simple and complete dialysis circuit setup. Lastly, we designed and tested a larger filtration device consisting of 6 channels in parallel (?6 ml/h) and obtained similar filtration performances. Further multiplexing is possible by increasing channel parallelization or device stacking to achieve higher throughput comparable to convectional blood dialysis systems used in clinical settings.

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.

Researchers at the Massachusetts Institute of Technology and the National University of Singapore have developed a technology which aims to treat sepsis in the blood using microfuidic techniques. The device, which comprises a series of microfludic channels, separates circulating bacteria and inflammatory components in the blood from the healthy red blood cells using a phenomenon known as margination. Margination normally occurs in blood vessels and causes bacteria and white blood cells to move to the side of the vessel.

The microfluidic channel network measures 20 micrometers high by 20 micrometers wide and is etched onto a polymer substrate where it handles the infected blood in three separate stages. As the infected blood flows through the first stage of the microchannel system, the harmful cells are directed towards the side walls of the channel. microfluidic sepsis diagram Microfluidic Device Filters BloodAt the second stage the microchannel divides into three separate channels: a central channel for the red blood cells and two side channels for redirecting the harmful cells. This filtering is repeated on the central channel in the final stage of the device to remove any remaining harmful cells in the blood.

The researchers have so far demonstrated up to 80 percent removal of the E. coli bacteria and greater than 80 percent depletion of inflammatory components from samples processed by the device. The results of these early experiments have been published online in the journal Biomicrofluidics. The researchers have also designed and tested a scaled up system consisting of six microfluidic channel networks in parallel for faster cleansing of blood samples.

source : http://bmf.aip.org/resource/1/biomgb/v6/i2/p024115_s1?isAuthorized=no

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