Competitive adsorption and functional activity of fibrinogen on polyurethane biomaterials surfaces.

An immunological atomic force microscopy technique was used to recognize fibrinogen adsorption and functional activity on polyurethane biomaterial surfaces in the presence of other proteins. The amount of fibrinogen adsorbed on surfaces as recognized by an antifibrinogen polyclonal antibody when in competitive adsorption with human serum albumin (HSA) or human IgG was found to be related to the molar ratio of proteins. A significant decrease in fibrinogen adsorption was observed only when the fraction of smaller proteins reached a threshold value, dependent on smaller protein properties. The functional activity of fibrinogen was measured by a monoclonal antibody recognizing a region containing the dodecapeptide sequence located at the C-terminus of the γ-chain, γ-400-411. Results show that the presence of smaller proteins affected the conformational structure of fibrinogen and increased the availability of platelet binding sites in fibrinogen adsorbed on surfaces. Platelet adhesion was performed on polyurethane surfaces, which were competitively preadsorbed with fibrinogen and HSA. Platelet adhesion correlated well with the functional activity of fibrinogen, measured after competitive adsorption on surfaces. The work suggests that platelet adhesion is not necessarily determined by the amount of adsorbed fibrinogen but is related to the activity of fibrinogen as measured by the availability of the platelet binding sites in the fibrinogen, γ-chain dodecapeptide.