Researchers have developed a novel technique to test platelet function in an individual’s blood sample which they claim is faster, easier, and more precise than existing methods.
An experimental study by researchers at Emory University in Atlanta, Georgia, USA, found the technology holds the potential to assess the effects of antiplatelet drugs on individuals and to gain a clearer picture of bleeding risks for patients undergoing cardiopulmonary bypass surgery.
Writing in Nature Biomedical Engineering, the team says it requires only a drop of blood to run tests, compared to the tablespoon needed for current assays.
The breakthrough is based on synthetic-DNA tension probes, which can detect cellular forces on the magnitude of just a few piconewtons – a force a billion times smaller than the weight of a paperclip. The researchers amplified the signal of the probes by using CRISPR-associated protein 12a, and the resulting fluorescent signal was detected using a routinely used plate-reader.
Co-leader of the study, Dr Roman Sniecinski from Emory School of Medicine’s Department of Anesthesiology, said: “Platelet function in general is important and yet the current tools that we have to measure it are relatively primitive. This new technique offers an easier, faster and cheaper way to measure platelet function, while also providing us with key information that we didn’t have before.”
Regulating platelet function is especially critical to people at higher risk for some conditions. While antiplatelet drugs, such as clopidogrel, ticagrelor and even aspirin, are commonly prescribed, these drugs may not work well and adjustments in doses or changing to another drug might better help prevent heart attacks. Platelet function becomes even more dysregulated during cardiac surgery.
Aggregometry, a standard tool used to assess platelet function, measures the speed and degree at which platelets aggregate, but it does not provide information about their level of activation.
The laboratory of Khalid Salaita, of Emory’s Department of Chemistry, is a leader in visualising and measuring the mechanical forces applied by cells using tension probes that are made from synthetic strands of double-stranded DNA tethered to a surface. When the cells bind and apply force to the anchored DNA, the DNA splits into two strands, leaving one strand stuck to the surface.
The resulting physical tug is converted into a fluorescent signal, but normally these are too infrequent, faint and very short-lived, so they can only be detected by specialist microscopes.
To get around this problem, the lab team used CRISPR associated protein 12a (Cas12a) and combined it with its tension probes to see if the enzyme would amplify the signal for the mechanical forces exerted by blood platelets.
In doing so, the team developed the Mechano-Cas12a Assisted Tension Sensor (MCATS), a precise and ultrasensitive tool that measures cellular traction forces generated by as few as 2,000 platelets within a sample. The resulting signal is robust enough to measure via a conventional fluorometer or plate reader.
To test its efficacy of measuring the activity of platelet function, the team used blood samples from healthy volunteers.
They went on to add to the healthy blood samples different antiplatelet drugs, ranging from over-the-counter aspirin to a panel of different prescription medications. The MCATS results showed the antiplatelet therapies reduced the mechanical activity of platelets by an amount similar to the reduction observed in aggregometry.
When testing blood samples from seven patients pre- and post-cardiopulmonary bypass surgery, they found the MCATS readings for the platelet activity of each patient’s sample correlated to their likelihood to need platelet transfusions to minimise bleeding after surgery.
Dr Sniecinski said: “The bottom line is that MCATS is a whole new way to measure platelet function using a really tiny sample.
“It’s telling us something specific that we haven’t been able to measure before and that can give us a new way to understand what’s going on with platelet dysfunction and the best methods for controlling it.”
Duan Y, Szlam F, Hu Y, Chen W, Li R, Ke Y, Sniecinski R, Salaita K. (2023) “Detection of cellular traction forces via the force-triggered Cas12a-mediated catalytic cleavage of a fluorogenic reporter strand.” Nature Biomedical Engineering, doi: 10.1038/s41551-023-01114-1
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