New chip-based test could revolutionize blood transfusions

A new, fast and easy test could revolutionize blood transfusions-giving blood centers and hospitals a reliable way to monitor the quality of red blood cells after they sit for weeks in storage. 

The project is a collaboration between engineers and medical researchers at the University of Colorado Boulder and University of Colorado Anschutz.

The team's device hasn't yet been approved for use. But the group hopes that it could one day help the United States better manage its precious blood supply.

The entire test also fits on a single chip, said Xiaoyun Ding, associate professor in the Paul M. Rady Department of Mechanical Engineering at CU Boulder.

Our vision is to have a chip the size of a dime that you can plug into your cell phone. It could use your phone's camera and an app to read out the results in just two minutes."

Xiaoyun Ding, associate professor, Paul M. Rady Department of Mechanical Engineering, CU Boulder

Ding and his colleagues published their findings in the latest issue of the journal Lab on a Chip.

The project focuses on a little-known problem in the medical world.

Every year, roughly 6.8 million people donate blood in the United States alone, helping save millions of lives, according to the American Red Cross. But just like groceries sitting on store shelves, red blood cells age over time. 

To track that aging process, Ding and study co-author Angelo D'Alessandro, an expert on red blood cells, turned to an unusual property: vibrations.

The team's device, known as a surface acoustic wave hemolysis assay (SAW-HA), jiggles red blood cells until they break apart-revealing valuable information about the health of those cells.

Think of it a bit like shaking a jar of salad dressing to break up clumps.

"We envision that this technology could help allocate higher-quality units to vulnerable patient populations, such as pediatric patients and patients with sickle cell disease who receive regular transfusions," said D'Alessandro, professor in the School of Medicine at CU Anschutz. 

Expiration date

When you donate blood, technicians will first separate your red blood cells from the rest of your blood, including the plasma and white blood cells. They then store your red blood cells at near-freezing temperatures.

Over time, some red blood cells lose their healthy, rounded shape and begin to look spikey. Eventually, they die and burst open through a phenomenon called hemolysis.

In the United States, blood centers can only store red blood cells for 42 days. But, D'Alessandro noted, blood from some donors ages faster than blood from other donors-potentially compromising the effectiveness of transfusions.

"Despite the central role of transfusion in modern medicine, routine quality control of red blood cell products after regulatory approval is remarkably limited," D'Alessandro said.

Shaken not stirred

The group's device is modeled around surface acoustic waves, or SAWs. They are similar to sound waves but move only over the topmost layer of a material. (Earthquakes, for example, generate waves that reverberate across the planet's surface and can cause serious damage).

The team first deposits a thin layer of metallic electrodes on top of a wafer made from a material called lithium niobate. The researchers then add a tiny drop of blood on top. When they pass an electric current through the device, the lithium niobate begins to vibrate wildly-shaking the blood.

Those vibrations cause the red blood cells to heat up, and they eventually undergo hemolysis, dumping their contents into the surrounding solution. 

The researchers suspect that older blood cells burst faster and at lower temperatures.

"When cells get older and older, their membranes become weaker and weaker," Ding said.

For the new study, the researchers tested the device by shaking real red blood cells from donors. 

Some blood samples, they found, hemolyzed at lower temperatures. Those samples also contained higher or lower levels of certain molecules, known as metabolites, that previous research has shown are associated with aging cells.

The team still has a lot of work to do before it can be used as a reliable indicator of red blood cell quality in real blood centers. But Ding noted that these "labs on a chip" could also help to screen human patients for a variety of diseases of the blood, including sickle cell disease.

"We can potentially measure anything that affects red blood cells or protein levels in the blood," Ding said.