Platelet Adhesion to Polyurethane Urea Under Cardiac Pulse

Open Access
Chorpenning, Katherine Ann
Area of Honors:
Bachelor of Science
Document Type:
Thesis Supervisors:
  • Keefe B Manning, Thesis Supervisor
  • William O Hancock, Honors Advisor
  • Margaret June Slattery, Faculty Reader
  • Steven Deutsch, Faculty Reader
  • platelet
  • adhesion
Platelet adhesion to an artificial surface is a key event in thrombus development for cardiovascular devices. Polyurethane urea (PUU) is one widely used biomaterial in the medical device industry today due to its desirable mechanical and blood compatibility properties. The goal of the present work is to test the platelet adhesion properties of PUU under simulated physiologic conditions. A rotating disk system (RDS) is used to deliver a “cardiac pulse” to a stainless steel disk with PUU attached to the bottom surface. This pulse simulates the mean velocities typically seen at the inlet of a left ventricular assist device during the cardiac cycle. Using a rotating disk provides a well-defined flow that spans a large shear rate range. The metal disk and material rotate in platelet rich plasma (PRP) obtained from bovine blood. Platelet adherence is quantified by immunofluorescent labeling using CAPP2A mouse anti-bovine αIIbβ3 antibody and Alexa-Fluor 488 donkey anti-mouse IgG. Two approaches were used to identify shear rates with high levels of platelet adhesion. The first method applied a cardiac pulse continuously to a 15 mm disk for 2 hr. The average adhesion coefficient (AC%) was 0.60% at the center, which is comparable to the values seen for a steady 2 hr rotation at 283 rpm (AC% = 0.36%). In the second study, platelets were pre-adhered to the material surface and a cardiac pulse was applied continuously for 30 min. At the disk center, 33% of the original platelet number remained following the 30 min pulse. This value decreased to 10% at 300 s-1 (3 mm radius) and 5% at 840 s-1 (8 mm radius). Steady rotation and cardiac pulse experiments all showed low platelet adhesion for shear rates higher than 500 s-1. This is the highest shear rate at which a platelet can adhere to a polyurethane surface and is a current standard for many cardiovascular applications.