Dual radiolabeling to study protein adsorption competition in relation with hemocompatibility

Human fibrinogen (Fg) and albumin (HSA) were labeled with (3)H and (14)C, respectively. Dual counting allowed the adsorbed amount of the two proteins to be determined simultaneously. Single adsorption, adsorption of the two proteins in competition, but also exchange (substitution by molecules of the same nature) and displacement (desorption under the action of the other protein) experiments were performed on two model surfaces, glass and polystyrene (PS), as well as on pure polyvinylchloride (PVC-s) and on PVC from blood bag (PVC-b). As expected, the adsorbed amount of a single protein is higher on a hydrophobic compared to a hydrophilic surface. When the two proteins are adsorbed in competition, they are found in equal proportion on glass, while HSA is twice more abundant than Fg on PS and PVC-s and about six times more abundant on PVC-b. This trend is related to an increase of the water contact angle of the substrates. For PVC-b, the contact angle is affected by the presence of aliphatic components exposed at the extreme surface, as determined by angle-resolved X-ray photoelectron spectroscopy. In exchange and displacement experiments, the first adsorbed molecules remain dominating on PS while they can be removed from glass. Given the known importance of HSA and Fg adsorption for the fate of materials placed in contact with blood, the method described in this paper may be used as a first approach to orient the design of surfaces with improved hemocompatibility.