A new study published in the journal Scientific Reports stated that blood stored in blood banks become stiffer in time.

Researchers from the University of Illinois used advanced optical techniques to account for the stiffness of the membrane that surrounds red blood cells. The team discovered that although cells continued to be the same shape throughout time due to its hemoglobin content, the membranes surrounding them become stiffer, leading to a decrease in functionality of the cells.

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Using an optical technique called spatial light interference microscopy (SLIM), light is able to measure cell mass and topology with nanoscale accuracy without disrupting its functionality. The said system is able to acquire images more than 100 times faster than its predecessor created by electrical and computer engineering professor Gabriel Popescu's lab in 2011. 

What the system revealed was that membranes lost their elasticity the longer they were stored. Elasticity is an important characteristic for blood cells because this trait allows them to travel through small capillaries and allows them to be permeable enough so that oxygen can pass through them.

Although stored blood continued to look like and flow like newly-harvested blood, the longer the blood is placed in storage, the less it carried oxygen into the miniscule microcapillaries of the body.

Blood banks have set a 42-day "shelf life" for blood. However, during those 42 days, researchers found out that blood can be damaged or rupture even though it continues to look like the day the specimens were collected.

According to  Basanta Bhaduri, the lead author of the paper, "In microcirculation such as that in the brain, cells need to squeeze through very narrow capillaries to carry oxygen. If they are not deformable enough, the oxygen transport is impeded to that particular organ and major clinical problems may arise. This is the reason why new red blood cells are produced continuously by the bone marrow, such that no cells older than 100 days or so exist in our circulation. " 

Krishna Tangella, professor of pathology and one of the researchers, shared that their findings can be applied in instances such as when a doctor needs to determine when red-cell transfusions should be administered on patients with anemia.