Platelet adhesion, aggregation, and embolism on artificial surfaces in non-parallel blood flow

Abstract

When using artificial surfaces that come into contact with the bloodstream, it is important to consider the undesirable consequences of thrombus formation and embolization. Although great progress has been made by creating new surfaces and antithrombotic coatings or evaluating flow conditions, unexpected platelet adhesion and aggregation can lead to the sudden formation of an adverse thrombus. Our experiments in a stagnation point flow chamber with citrate-anticoagulated whole blood and ADP-stimulated platelets mimicked the situations of implanted artificial organs, e.g., mechanical circulatory support devices, or extravascular circulation. With video microscopy, real-time platelet characteristics were observed at shear rate levels between 50 and 500 s−1 on glass, von Willebrand factor, and polyurethane surfaces for at least 5 min after the first contact. Platelet adhesion and aggregation were observed with distinctness in aggregate size, surface coverage, aggregate size, probability of an embolic event, and platelet contraction. The probability of an embolic event increased at lower flow rates. Additionally, platelet contraction was affected by the flow rate. Raising the flow rate intensified the platelet contraction. With this setup, the microembolization caused by surface contact and flow and platelet contraction can be detected in a real-time direct observation. This capability addresses both technical and clinical issues, such as thrombus and embolus formation, and may improve the research on the hemocompatibility of biomaterials.