Novel device measures stiffness and stickiness of red blood cells

Researchers have created a versatile device that measures two important properties of red blood cells that are relevant for sickle cell and other diseases: deformation and adhesion.

The team, from Case Western Reserve University (CWRU) in Cleveland, OH, describes the innovative device - a microfluidic platform with a computer algorithm that does the math - in a paper published in the journal Technology.

Sickle cell disease is a group of inherited red blood cell disorders. People with the disease have abnormal hemoglobin - the protein that carries oxygen - in their red blood cells. The abnormal hemoglobin is called sickle hemoglobin.

Red blood cells containing normal hemoglobin are flexible and shaped like a doughnut with a thin flat area in the middle instead of a hole. This allows them to squeeze round bends in blood vessels and through smaller ones to deliver vital oxygen to tissues and organs.

However, sickle hemoglobin has a tendency to form stiff rods inside the red blood cell - changing it into the crescent or sickle shape that gives the disease its name.

Red blood cells containing sickle hemoglobin are less flexible than normal red blood cells and also tend to be stickier. These two features increase the risk that they will cause a blockage in a blood vessel and impede the delivery of oxygen to nearby tissues and organs.

When such a blockage occurs, it causes a sudden and severe attack of pain - called a pain crisis - that is typical of sickle cell disease. Pain crises occur without warning and often require hospitalization for effective treatment.

In extreme cases, the blockage of blood vessels in sickle cell disease can lead to widespread organ damage and early death.

Currently, the only way to cure sickle cell disease is with a stem cell transplant. But unfortunately, most patients are either too old for a transplant or do not have a relative with a good enough genetic match to receive transplantable stem cells from.

Effective treatments exist and these can reduce symptoms and prolong life. Early diagnosis and regular monitoring to prevent complications also helps.
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Potential monitor of disease progression

By assessing the extent of stiffness and stickiness, or the "dynamic deformability and adhesion," of red blood cells, the new microfluidic device offers great potential as a way to monitor progression of sickle cell disease, note the researchers.

They say the device could also help with research and developing new treatments for sickle cell disease.

Other ways to measure stiffness and stickiness in red blood cells - such as atomic force microscopy and optical tweezers - do exist, but they do not lend themselves to working with whole blood in a clinical setting, say the researchers.

They note their device can assess the stiffness of a single red blood cell, and also, by mimicking blood vessel properties, assess the stickiness of red blood cells from whole blood of sickle cell patients.

Lead investigator Umut Gurkan, an assistant professor in CWRU's Department of Mechanical and Aerospace Engineering, says:

"The microfluidic system developed here has the potential to be used in a high-throughput manner with an integrated automated image processing algorithm for measurement of RBC [red blood cell] deformability and adhesion in patients' blood."

The authors explain that healthy red blood cells undergo reversible deformation when they circulate around the body in blood vessels. They respond to "fluid shear stresses" extremely fast - they can bend and regain their shape in the space of 100 milliseconds.
'Interplay between dynamic deformability and increased adhesion'

To assess dynamic deformability of red blood cells, the researchers used what they call a dynamic deformability index (DDI), which they define as "the time-dependent change of the cell's aspect ratio." Essentially, a cell's DDI is a measure of how quickly it springs back to its normal shape after experiencing flow shear stress.

In their paper, the team describes a range of tests where they measured the DDI of deformable and non-deformable red blood cells.

The researchers also compared adhesion of deformable and non-deformable red blood cells from blood samples taken from sickle cell patients. They tested the stickiness of the cells under different flow shear stresses - both within and outside ranges experienced in normal blood vessels.

They found that at flow shear stresses "well above the physiological range," non-deformable sickle red blood cells were much stickier than deformable sickle red blood cells, "suggesting an interplay between dynamic deformability and increased adhesion" of red blood cells when blood vessel blockage occurs.

The team suggests the device may also be useful for studying the deformation of cells that could be relevant in other diseases - such as diabetes, malaria and the bone marrow disorder polycythemia vera.

The researchers plan to study red blood cell stiffness and stickiness in more sickle cell disease patients so they can link the two properties with other disease and patient characteristics.

As the technology for making them becomes cheaper and more widely available, more and more researchers are using microfluidic devices in all kinds of ways to investigate, diagnose and perhaps even treat disease.

For example, Medical News Today recently learned how an "IVF chip" incorporating microfluidics with imaging techniques enabled researchers to film a single sperm fusing with an egg cell.

And in May 2015, another article described how scientists are using microfluidic technology to develop new immunotherapy vaccines. Using microfluidic technology, they can squeeze immune system B cells so their membranes develop temporary holes through which antigens that program specific immune responses can be inserted.

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Novel device shows promise to predict sepsis

Researchers have developed a new computer-aided model to identify early symptoms of sepsis-- a potentially life-threatening condition caused by the body's response to an infection.

Sepsis is a major cause of death in hospitals, and early detection is key to preventing deaths. Every hour of delay is linked to a 7 per cent reduction of survival. 

The study showed that the computer-aided National Early Warning Score (cNEWS) determined if it could enhance the accuracy of predicting sepsis. The score can trigger screening for sepsis within 30 minutes.

"The main advantage of these computer models is that they are designed to incorporate data that exist in the patient record, can be easily automated and place no extra burden on the hospital staff to collect additional information," said a Prof.

"These risk scores should support, rather than replace, clinical judgment. We hope they will heighten awareness of sepsis with additional information on this serious condition," he added, in the paper published.

cNEWS will now be introduced carefully into hospitals with appropriate information technology  infrastructure, the study noted.
 

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Novel device detects bacteria and suggests apt antibiotic

An interdisciplinary team of engineers and pharmaceutical researchers at the University of Alberta has invented a device that can rapidly identify harmful bacteria and can determine whether it is resistant to antibiotics. The device could save precious hours in patient care and public health, and prevent the spread of drug-resistant strains of bacteria. The team's findings can help in detecting bacteria and measure their susceptibility to antibiotics in small confined volumes.
The device was designed to look for and trap different types of bacteria and find out which antibiotics are most effective against them. Rather than growing bacterial cultures then testing them, the microscopic device relies on nano-scale technology for fast results.
The main feature of the device is a cantilever, a plank that resembles a diving board that has a microfluidic channel 25 times smaller than the width of a hair etched on its surface. The channel is coated with biomaterials, like antibodies, that harmful bacteria like E. coli or Listeria in fluid samples stick to.
When bacteria are caught, the device sends out three different signals to the researchers. When bacteria is detected, the cantilever's mass changes, and it bends, explained researcher Thomas Thundat.
"So, this gives us two signals: the mass change and the bending action by shining infrared light on the bacteria, a third signal is sent. If the bacterial absorbs the light, it begins to vibrate, generating a minute amount of heat that sends a confirmation signal. Having three detection methods means there is no ambiguity".
"By monitoring the interaction of light and bacteria, we can get highly selective detection of bacteria," said Faheem Khan, another expert.
With the bacteria trapped in the cantilever, different antibiotic drugs can be added to the device. Changes in the intensity of tiny oscillations of the cantilever signal will inform the researchers whether the bacteria are alive or dead. The researchers then know which antibiotics the bacteria are susceptible to.
"We're trying to find a way to fight bacterial resistance to drugs and prevent or at least decrease the spread of drug-resistant strains," said Hashem Etayash, a researcher. Adding, "We're able to do several tests in a very short period of time and we can quickly identify bugs that can resist antibiotics." 

 The device can be used to test extremely small fluid samples, millions of times smaller than a rain droplet. The size of the device is advantageous when you only want a very small sample, in settings such as a neonatal intensive care unit, or in situations where only very small samples are available.

The research was published in Nature Communications journal. 

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