The Effects of Hematocrit and Rotation Time on Platelet Adhesion to a Polyurethane Urea Surface

Open Access
- Author:
- Grunenwald, Lauren Elizabeth
- Area of Honors:
- Bioengineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Dr. Keefe B Manning, Thesis Supervisor
Dr. Keefe B Manning, Thesis Honors Advisor
Margaret June Slattery, Faculty Reader
Christopher Alan Siedlecki, Faculty Reader - Keywords:
- platelet adhesion
rotating disk
polyurethane urea - Abstract:
- Cardiovascular disease (CVD) has been the leading cause of death in the United States since 1900. CVD affects nearly 82.6 million American adults, and, on average, it claims one life every 39 seconds. Ventricular assist devices are a viable option for sustaining patients awaiting cardiac transplantation, but postoperative complications, such as bleeding, infection, and thrombosis, still remain an issue. Platelet adhesion to the plasma protein-coated polyurethane urea (PUU) blood sac in the Penn State 50 cc ventricular assist device is a primary event in thrombosis. Prior to adhesion, platelets must be convected to the material surface. Red blood cells have been shown to increase platelet diffusivity as a function of shear rate through localized mixing and cell-cell collisions and as a function of shear rate and hematocrit through platelet margination. In this study, we aim to determine the effects of hematocrit (Hct) and rotation time on platelet adhesion to PUU. A rotating disk system is used to provide a steady waveform to the PUU surface. The disk is rotated in either 20% Hct or 40% Hct reconstituted whole bovine blood for 0.5, 1, or 2 hours. Adhered platelets are immunofluorescently labeled with a primary CAPP2A mouse anti-bovine antibody and a secondary Alexa-Fluor 488 donkey anti-mouse IgG, and the PUU material is imaged at specific locations using confocal microscopy. The shear rate at each imaging location is experimentally determined using laser Doppler velocimetry. Platelet adhesion is quantified by the average platelet counts at each radial location and by calculating an adhesion coefficient from the average platelet count, platelet flux, and rotation time. The platelet fluxes and raw counts are lowest at the disk centers and increase logarithmically with shear rate. The platelet counts are an order of magnitude greater in whole blood than platelet rich plasma. After two hours of rotation, the adhesion coefficients were highest at the disk centers and were approximately 0.15% for the 20% Hct condition and 0.20% for the 40% Hct condition.