Adsorption of Hageman factor (factor XII) and other human plasma proteins to biomedical polymers.

Protein adsorption to surfaces occurs whenever blood comes into contact with biomaterials, prosthetic devices, and artificial organs. The plasma protein Hageman factor (factor XII) present at the interface between blood and foreign surfaces can be qualitatively and quantitatively detected after in vitro perfusion of anticoagulated human blood through important biomedical polymers. We have determined protein adsorption by a modified radioimmunoassay and by scanning electron microscopy using immunogold labeling techniques. The materials used included vascular graft materials (Dacron and expanded polytetrafluoroethylene) and the National Heart, Lung, and Blood Institute-Devices and Technology Branch reference materials polydimethylsiloxane, polyethylene, and silicone rubber. Factor VIII-von Willebrand factor, another trace plasma protein, and other plasma proteins such as fibrinogen, immunoglobulin G, albumin, fibronectin, and hemoglobin were also detected at the blood-contacting surface. At physiologic flow rates, the adsorption of these proteins from the circulating blood to the surface of these materials appears to be a function of time, with certain materials, as well as of the physical and chemical characteristics of the material surface. Hageman factor adsorption to surfaces, quantified under static conditions, occurs at nanogram concentrations. These data suggest that trace proteins, such as those important in the activation of the coagulation cascade, can significantly affect the blood compatibility or thrombogenicity of an implanted device.