Microfluidics and Microscopy Deliver a Better Blood Clot Diagnostic

A new method using advanced microfluidics and miscroscopy could offer clinicians a better way of detecting blood clots to prevent strokes and heart attacks. 

by Menaka Wilhelm
November 05, 2018

Researchers have developed a process that could provide a more accurate way of detecting blood clots and predicting sooner than usual whether the clots can cause strokes or heart attacks. The team, from Australian National University, uses a unique system that combines a microfluidic device and a customized holographic microscope. 

Clotting is a key part of healing wounds. It occurs when blood platelets adhere to the collagen and other proteins found on a wound. This causes them to release a variety of biochemicals that activate thrombin, an enzyme that triggers clotting and wound recovery. 

But under the wrong conditions a thrombosis, or clot in a blood vessel, can cause a stroke. While clinicians understand the risk factors of clotting, they have few tools to assess the real dangers clots pose to a patient. 

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The new technique takes a more holistic approach than the blood testing clinics currently use, said Elizabeth Gardiner, a biologist at the John Curtin School of Medical Research who worked on this new diagnostic approach. Today’s clinical approaches focus on quantifying components within a blood sample, such as platelet counts, concentration of clotting proteins, and protein activity. But those individual pieces do not always sum to a patient’s whole risk, Gardiner said. 

“What you need to know is the function of those platelets,” she said. 

To do that, the team developed a diagnostic method that assesses how a patient’s blood forms clots, complementing standard blood-testing metrics with a more comprehensive measurement. 
The researchers begin by placing a small amount of blood into a microfluidic device that has collagen-coated channels, which mimic the interior of a blood vessel. A mechanical cue—shear stress generated by flowing blood through the channels rapidly—prompts the platelets and red blood cells to adhere to one another and form a clot. 

Measuring a clot formation, though, is difficult. The flat, round shape of a red blood cell makes it difficult to collect a good image. 

“The optical properties of a red blood cells are almost akin to small little lenses floating around,” said Steve Lee, an optics expert who led the microscopy component of this diagnostic.

To deal with this optical scattering, Lee and his team developed a microscope that relies on holographic microscopy methods. This technique does not require the antibody-based labeling required in fluorescent microscopy, and it also uses a less intense light source. “We use even less light than a laser pointer,” Lee said. 

To measure the clot’s size and shape, the microscope’s optics split a beam of laser light into two paths. One beam hits the sample, while the other travels through air. Moving through the clot delays light’s motion more than moving through air, so when the two light beams recombine, their differences generate a hologram. 

A camera records the image and an algorithm analyzes the digital reconstruction of the hologram to quantify several of the clot’s parameters, including area, volume, peak height, and dry mass. Data processing takes about 20 minutes. 

Developing the software to quantify these parameters took about the same time as constructing the holographic microscope, Lee said. The team continues to build their own customized components for the microscope to help make the technology more accessible to ordinary clinics. 

The team is now collaborating with a machine-learning research group to parse the large amount of data generated by the holograms. Gardiner and Lee argue that crunching data on such a largescale is good preparation for assessing how the parameters of a blood clot could affect the patient’s outcome. 

They believe the new system can eventually give clinicians a better sense of the factors that drive thrombosis and the preventative measures that could save lives. 

Menaka Wilhelm is an independent writer.

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