Adsorption of plasminogen from plasma to lysine-derivatized polyurethane surfaces

The adsorption of plasminogen, the principal protein of the fibrinolytic pathway in blood, to a number of solid surfaces from plasma was investigated. This study forms part of a larger project to develop a fibrinolytic surface for blood-contacting applications. Polyurethanes incorporating lysine residues were developed in an attempt to promote selective adsorption of plasminogen from plasma through lysine-binding sites in the plasminogen molecule. The adsorption of plasminogen to these surfaces as well as to glass, 'conventional' polyurethanes and precursor sulphonated polyurethanes was investigated. Adsorption from citrated human plasma diluted with isotonic Tris buffer (pH 7.4) was measured under static conditions at room temperature using radioiodinated plasminogen. The following trends were observed. (1) Adsorption increases monotonically with increasing plasma concentration and there is no suggestion of transient adsorption (Vroman effect) on any of the surfaces studied. (2) Sulphonate groups appear to have a strong effect on plasminogen adsorption as was found previously for adsorption from buffer. (3) The lysine-derivatized material having the highest lysine content may show a slight increase in plasminogen binding affinity compared to its sulphonated precursor.