Scientific and engineering criteria necessary for the design of biocompatible materials have not yet been developed, partly because the mechanisms involved in the foreign body reaction or thrombosis remain largely undefined. The behavior of proteins and cells at surfaces control these mechanisms, and this proposal therefore is focused on these events. The organization of the adsorbed protein layer is thought to determine specific cellular responses which in turn determine the overall biological reaction to implanted materials. To test this hypothesis, the adsorption of proteins important in the reactions of three cell types will be measured under conditions giving rise to differences in the organizational state of the adsorbed proteins. Methods to change the state of the adsorbed protein include variations in the surface chemistry, shear rate, and adsorption time, and concentration of the protein solution. The protein-cell pairs to be studied include: 1) fibronectin adsorption in serum compared to 3T3 cell spreading; 2) immunoglobulin G and complement C3 adsorption from tissue fluid compared to macrophage spreading; and 3) von Willebrands factor and fibrinogen adsorption from plasma compared to platelet adhesion and release. To further understand how the adsorbed protein layer is organized, we intend to extend previous studies of protein adsorption to more complex systems, namely, recalcified plasma and peritoneal tissue fluid. The influence of shear rate, mass action and mass transfer on the composition of the adsorbed layer will be studied in these systems. The role of cooperative mechanisms enhancing surface activity due to protein-protein interactions will be investigated. The ability of cells to process adsorbed proteins into altered forms will be examined. A relation between surface affinity of proteins and the acid-base character of the polymer will be sought. ESCA examination of proteins at interfaces as well as the polymers themselves will be employed in these studies. Since the affinity of proteins for surfaces is a fundamental, but as yet been unmeasured, parameter in understanding their interfacial behavior, several techniques for determining surface activity will be evaluated, including competition in binary mixtures and a high shear flow cell for protein detachment studies.
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