In vitro blood-materials interactions: a multi-test approach

The purpose of this dissertation is to evolve a series of simple in vitro blood test with well-defined protocols specifically designed to evaluate the ability of materials to activate known pathways of coagulation. Concurrently, a series of well-defined polymers are characterized according to surface energetics, change, and surface mobility (entropy) to provide a surface profile of the test materials. The physical and blood characterization data are use to test the minimal interfacil free energy hypothesis, the hydrophobic-hydrophilic ratio hypothesis, the negative surface charge hypothesis, and the surface mobility hypothesis. The data suggest that the minimal interfacial free energy hypo-thesis in not supported by the majority of test used in this study. The hydrophobid-hydrophilic ratio of the surface of selected materials does correlate with improved blood materials interactions, but this hypothesis is not predictive of blood interactions with all materials tested. Negatively and positively charge groups can apparently act independent of the hydrophobic-hydrophilic nature to improve blood compatibility. Changes in blood interactions resulting from a change in the entropy of the surface is apparent for platelet adhesion, but is not predictable for whole blood clotting time. The results reported here suggest that platelet adhesion to a material may improve its compatibility with blood. No single surface property of individual blood test can determine blood compatibility in a general sense. A multiparameter in vitro approach is necessary to optimize material for in vivo use.