In the present study a two step enzyme immuno assay (EIA) was used for the investigation of the adsorption of proteins and lipoproteins from solutions and from blood plasma onto polymer surfaces. It was found that only a small adsorption of the major blood proteins occurred from plasma. Evidence is presented that the reason for this adsorption behaviour is a preferential adsorption of high density lipoprotein (HDL).

The adsorption of antithrombin III (AT Ill) onto polystyrene surfaces preadsorbed with albumin or albuminheparin conjugates was studied using a two step enzyme immuno assay. When AT Ill-buffer solutions were used the highest adsorption values were measured on high affinity albumin-heparin conjugate pretreated surfaces.Less AT III adsorption was found on nonfractionated albumkheparin conjugate preadsorbed surfaces. AT III adsorption could also be detected on low affinity conjugate and albumin coated surfaces When AT Ill was adsorbed from plasma or plasma dilutions with buffer, only AT III on surfaces preadsorbed with high affinity or nonfractionated albumkheparin conjugate was found. These results demonstrate that the heparin moiety of the conjugate is directed to the solution phase whereas the albumin moiety contacts the polystyrene surface.

SUMMARYThe competitive adsorption of human serum albumin (HSA), human immuno-7-globulin (HIgG) and human fibrinogen (HFb) onto polystyrene (PS) at 20°C and a pH of 7.35 (phosphate-buffered saline) was studied. Protein adsorption was studied using enzyme immunoassay. The results obtained with the immunoassay were compared with those obtained using radiolabelled proteins. Recent studies revealed that the adsorption behaviour of radiolabelled proteins onto surfaces differs from that of the non-labelled proteins, which may lead to misinterpretation of adsorption data. Differences in the adsorption behaviour of the labelled proteins as compared to non-labelled proteins can possibly be explained by the formation of modified proteins during the labelling procedure as shown by ion-exchange high-performance liquid chromatography (HPLC). The competitive adsorption of HSA, HIgG and HFb onto a PS latex was studied by measuring the depletion of proteins in solution. The decrease in protein concentration in solution was determined by HPLC techniques. A strong preferential adsorption of HFb was observed with maximum adsorption values of 0.6 ug/cm 2.

A few studies on the adsorption of plasma proteins to polymeric surfaces show that major plasma proteins: albumin (Alb), fibrinogen (Fb) and immunoglobulin (IgG) are adsorbed in much smaller quantities from plasma than from protein solutions ( 1 , Z ) . Present results show that this difference in adsorption is due to the preferential adsorption of high density lipoprotein from plasma onto the material surfaces studied (PVC and PS).