Platelet Adhesion Testing

A platelet adhesion test was developed to evaluate the adhesion of platelets to the preserved UV segments. Sheep blood Na heparin (Lampire Biological Laboratories, Pipersville, PA) was kept in the refrigerator for up to a day before use. The blood was warmed up to 37°C and quinacrine dihydrochloride (mepacrine) was added(0.0047 g/L) to label the platelets. Mepacrine is a fluorescent dye that does not affect platelet function [13–15]. Fresh (n = 2 veins), static (n = 3 veins), and bioreactor (n = 7 veins) veins were tested as well as control silicone tubes with 3-mm × 5-mm-thin bovine collagen sheets in an exposed window as controls (DSM Biomedical, Exton, PA; n = 5 tubes). Static samples and the control silicone tubes with collagen sheets were inserted into couplings in the bioreactor before testing. The bioreactor was warmed up to 37°C, mepacrine was mixed in the blood for 30 minutes, and blood was pumped through the veins and collagen grafts for 30 minutes at flows of 150 mL•min•vein that corresponded to ~5 dynes/cm² shear stress. Upon completion, the veins were drained and rinsed gently with saline, cut open longitudinally, and placed in a dish with a small amount of saline. The veins were imaged under fluorescence with 488 nm filter using Axio Observer Z1 inverted microscope (Carl Zeiss, Jena, Germany). Platelet counts were obtained by averaging platelet numbers over 6 high-power fields.