Abstract

Integrated Platelet Assays on a Microfluidic Platform

Sehyun Shin, Professor & Director, Korea University

Aggregation and adhesion of platelets to the vascular wall are consequences of platelet activation and these cascade processes play critical roles in hemostasis and thrombosis at vascular injury sites. In this study, we designed a simple and rapid assay of platelet aggregation and adhesion in a microfluidic system. To activate platelets, either shear stress or agonists was selectively chosen for the required test. For shear-induced platelet activation (SIPA), a rotating stirrer in a circular chamber was designed with considering shear generation with secondary-flow-induced mixing. Agonists such ADP, epinephrine and arachidonic acid were carefully combined with collagen or fibrinogen. When platelets were activated in whole blood, they were driven through the microchannel under vacuum pressure. Activated platelets adhered to a collagen or fibrinogen-coated surfaces on microchannel, causing blood flow to significantly slow and eventually stop. In order to conduct the above whole test with quick and easy operation, a microfluidic chip was carefully designed with mimicking in vivo environment. To measure platelet adhesion and aggregation, the migration distance (MD) of blood through the microchannel was monitored. As degree of platelet activation increased, MD gradually decreased. For platelet-excluded blood samples, the blood flow did not stop even at the end of microchannel. These findings imply that either SIPA or agonist-induced platelet activation can be examined with the present proposed microfluidic system. Also, the MD is a potentially valuable index for measuring the degree of platelet activation and aggregation. The proposed microfluidic system can examine various anti-platelet drug tests with rapidity and simplicity, which is of potential to be used at any point-of-care.