Microfluidic technology could help unravel the complex role of clot formation in bleeding disorders. 

A microfluidic device, designed by Scott Diamond and Keith Neeves from the University of Pennsylvania in Philadelphia, US, can be used to examine how platelets are recruited and aggregate into clots when a blood vessel is injured.

The device is unique in that it introduces platelet activators, known to play a critical role in clot formation, at a controlled rate into bloodflow outside the body. 'Our group is interested in developing technologies that mimic features of in vivo blood vessels using flow-based in vitro systems,' says Diamond. 

Platelet activators (blue) mix with blood flowing through a microfluidic device (top) causing platelet aggregation (bottom)

The set-up is based on a three-layer system: a top channel containing blood flowing under physiological conditions, a perpendicular channel containing activator solution, and a polycarbonate membrane between. A controlled amount of activator can be released into the blood channel through gaps in the membrane. The researchers can then easily dismantle the device after different experiments to examine how the conditions affect platelet aggregation on the membrane.

Diamond explains that, by helping scientists to understand platelet aggregation, the device could be of use for medical research. 'The mechanisms that contribute to clot stability or instability would be useful information in identifying therapeutic strategies for genetic blood disorders, such as haemophilia,' he says. 'Another potential application is flow-based drug screening of anti-platelet therapies to prevent heart attacks and strokes.'  

Diamond adds that a future challenge will be proving these in vitro techniques can yield results that are as good as or better than animal models for predicting how well such new therapies will work. 'In vascular injury, for example, there is a complex interplay between the extracellular matrix, platelets and cells. Currently, no in vitro system can probe all of these interactions,' he admits. 'However, advances in microfluidic and patterning techniques allow a very large parameter space to be explored in a combinatorial manner with minimal volumes of reagents and tissue.' 

Stephen Wilkes