Abstract-Fibrinogen adsorbs spontaneously from aqueous media containing that protein to droplets of liquid hydrophobic phases dispersed in those same media. Examples of such phases include mineral oils, straight-chain hydrocarbons, and various plant-and animal-derived oils. Lecithin preexisting on the surface of oil droplets reduces significantly the amount of fibrinogen that can otherwise bind to them. When bound, fibrinogen remains active in the classic sense of fibrin gelation. As a consequence, oil droplets coated with fibrinogen can participate in a host of biologically important adhesive processes in which the protein would be expected to participate. Certain polyanions, eg, heparin, pentosan polysulfate, dextran sulfate, and suramin, bind to adsorbed fibrin(ogen) and prevent thrombin-dependent adhesion of fibrinogen-coated surfaces. Thus, these polyanions can be used to prevent adhesion between fibrin(ogen)-coated oil droplets and other fibrin(ogen)-coated surfaces. Potential practical applications and biological implications of these phenomena are presented and discussed.

Implanted polymeric materials frequently elicit an inflammatory response characterized by the accumulation of both proteins and macrophages. Since the adsorption of proteins to an implant is immediate, inflammatory cells likely never make contact with the material itself; rather they interact with the adsorbed proteins. The proteins that predominate in this adsorbed layer include fibrinogen, albumin and immunoglobulins. ' Fibrinogen, which plays a central role in blood coagulation, collects at sites of inflammation. Implanted materials to which fibrinogen adsorbs also attract large numbers of macrophages.* Importantly, macrophages themselves bind fibrinogen? Whether this binding is receptor-mediated or not, it indicates interaction between macrophages and fibrinogen, supporting the notion that coagulation and inflammation are intimately related.3Tissue macrophages and their precursor cells, monocytes, are part of the mononuclear phagocyte system (MPS). A major function of these phagocytes is to dispose of bacteria and damaged or dying cells.',4 Phagocytosis involves the attachment of particles to the cell surface, ingestion of particles by the cell, and digestion of the particles within the cell. The capture of foreign particles by cells of the MF'S as well as the focal localization of those cells is believed to be mediated by adsorbed plasma protein^.^" Clearly, much about inflammation could be learned from studying the interactions of fibrinogen, macrophages and surfaces.In this work, microscopic polystyrene-divinylbenzene beads coated with selected members of a series of PEO,PPO,PEO, copolymers were used to examine the interactions of monocyteshacrophages with surfaces. These particular triblock copolymers were chosen for this study because by simply changing the ratio of their PEO and PPO segment lengths, the amphiphilic character of the surface to which they are adsorbed could be altered. Some of these copolymers are adjuvants, promoting cellular accumulation and inflammation'.*; others are inn0cuous.6~~-"