Adsorption of plasminogen from human plasma to lysine-containing surfaces

The objective of this work is to develop blood-contacting surfaces that wil l dissolve nascent clots that may begin to form on them. Surfaces were prep ared consisting of a polyurethane to which a coating reagent was attached c ovalently by photochemical methods. The coating reagent was a polyacrylamid e with lysine and benzophenone (for photochemical attachment) moieties pend ant to the chains. It was hypothesized that via the lysine moieties such su rfaces would show specific binding affinity for plasminogen, the principal component of the fibrinolytic system in blood. Surfaces of varying lysine c ontent in which the lysine was bound through the alpha-amino groups, leavin g the epsilon-amino groups free, were investigated. A control surface in wh ich the lysine was bound through the epsilon-amino groups was also examined . Advancing water contact angles showed the surfaces to be hydrophilic. Hyd rophilicity was found to decrease as the lysine content increased. Adsorpti on of plasminogen from plasma was studied using radioiodinated plasminogen as a tracer. For the epsilon-lysine surfaces, adsorption increased with inc reasing lysine content and reached a value of 1.2 mu g/cm(2) for the surfac e with the highest lysine content, that is, in the range expected for a com pact monolayer of plasminogen. The control surfaces, which contained either no lysine or lysine in which the epsilon-amino groups were unavailable, ad sorbed very small amounts of plasminogen. Immunoblots were obtained for the proteins eluted from the surfaces after incubation with plasma. For the co ntrol surfaces, most of the proteins tested for (some 20 in all) were prese nt. However, for the surface containing the highest concentration of epsilo n-lysine, only plasminogen was detected in a significant amount. It is conc luded that the epsilon-lysine surface adsorbs plasminogen to the exclusion of the other plasma proteins. Studies to examine the fibrinolytic propertie s of these surfaces will constitute the next phase of this work. (C) 2000 J ohn Wiley & Sons, Inc.