Wednesday, May 2, 2012

Tiny branch-like device can clean blood

Blood is sometimes referred to as the elixir of life, as it provides all tissues in the body with the required nutrients and oxygen. Without the complex system of blood vessels, organisms would never be able to grow larger than a tiny clump of cells. Therefore, our blood is well protected. It is tightly regulated, because small changes in its contents can have big consequences on the body's functioning. Bacterial infections are a constant threat: getting them into our tissues is bad, but pathogens in the blood represents a life-threatening situation. When bacteria infect the blood, it is called sepsis, and it is met with a powerful response of the immune system. This response is so powerful, it can result in death of the patient. Ridding the blood of whatever it is that does not belong there is therefore of paramount importance, which is why scientists from the University of Singapore have developed a device to clean it.

The main component of blood are the red blood cells. They carry oxygen, and typically make up 40-45 percent of the blood volume in weight. Leukocytes, guardians belonging to the immune system, and thrombocytes, involved with clotting, make up a small proportion of the blood. Because red blood cells, also known as erythrocytes, are relatively big, it is possible to 'filter' them through tiny channels. The device from the Singaporean scientists consists of a branched-like structure with channels that separate the red blood cells from the leukocytes and thrombocytes, because the latter two are significantly smaller. The same goes for microbes, that can move through the same, smaller channels as leukocytes and thrombocytes.

It is possible to separate microbes and leukocytes from the blood by mimicking a process called margination. Because leukocytes are part of the immune system, they guard and roam the blood. Sometimes it is necessary to move them to a site of inflammation, requiring them to leave the circulatory system. The process by which this happens is called margination or leukocyte extravasation. Basically, cellls squeeze themselves through the vessel wall, leaving the blood and moving into the tissues. Bacteria can do the same thing.
Margination: cells from the immune system move  from the blood (bottom), by squeezing through the cells that make up the blood vessel wall, and move into the tissues. 

Inside the artificial branch-like structure, scientists were able to get rid of 80 percent of the bacteria when testing their device with infected blood containing the intestinal bacterium E. coli. Blood containing the baker's yeast S. cerevisiae was filtered for about 90 percent. Additionally, components of the immune system, that can provoke a deadly attack during sepsis, were also shown to be filtered out. This would reduce the inflammation, and therefore the risk of a patient dying due to the body's response to a pathogen invading the blood. The remaining red blood cells and blood plasma, flowing through different channels, can return to the patient after the filtering process is complete.

So far, the device has only been tested using lab-prepared blood. The next step is to test the device in animals, to see if it works in live organisms with a functioning circulatory system. Scientists will need to prove that their system leaves functioning red blood cells after being separated from other blood contents. Additionally, speed will be of the essence, as sepsis can result in death rather fast. It remains to be seen whether the filtering process is fast enough to actually save someone's life. 

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