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Red blood cell topography (Image 2)

Map of membrane fluctuations in a normal red blood cell


Map of membrane fluctuations in a normal red blood cell, on average up to 50 nanometers. Measuring these fluctuations over time using spatial light interference microscopy (SLIM), researchers found that the membranes stiffen as they age, which impedes the cells function.

Researchers at the University of Illinois (U of I) used SLIM to measure the stiffness of the membranes surrounding red blood cells over time and found that although the cells retain their shape and hemoglobin content, the membranes get stiffer, steadily decreasing the cells' functionality. So while blood may look good on the surface, its functionality is degrading steadily with time.

Nearly 14 million units of blood are collected and stored annually in the U.S., with an estimated shelf life of 42 days. While blood cells can become damaged or rupture in storage, much of the blood keeps its shape and by all appearances, looks the same as it did the day it was donated.

Gabriel Popescu, an electrical and computer engineering professor at U of I, and his colleagues wanted to quantitatively measure blood cells over time to see what changed and what stayed the same to help determine what effect older blood could have on a patient.

The researchers used time-lapsed images of cells to measure and chart their properties. This included measuring nanometer-scale motions of the cell membrane, which are indicative of the cells stiffness and function--the fainter the membrane motion, the less functional the cell.

While the measurements revealed that a lot of cell characteristics stay the same over time, there were some changes: The membranes become stiffer and less elastic as time goes by. This finding is important because blood cells need to be flexible enough to travel through tiny capillaries and permeable enough for oxygen to pass through.

The researchers hope that the SLIM imaging method will be used clinically to monitor stored blood before it is given to patients, since conventional white-light microscopes can be easily adapted for SLIM with a few extra components.

This research was supported in part by National Science Foundation grants CBET 08-46660 and CBET 10-40462. [See related image Here.] (Date of Image: September 2014)

Credit: Gabriel Popescu, University of Illinois at Urbana-Champaign

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