Protein adsorption studies on 'standard' polymeric materials

Adsorption of fibrinogen from buffer as a single protein and from plasma to four materials has been studied. The two NIH-NHLBI primary reference standards, filler free polydimethylsiloxane and low density polyethylene, were used along with polyvinylcholoride and cellulose materials supplied by the IUPAC Working Party. The materials were examined in both film and tubing form, except for polydimethylsiloxane which was studied only in tubing form. Adsorption was measured at room temperature using 125I-labelled fibrinogen. The order of adsorbed amounts in the single protein experiments was found to be: cellulose < PVC < PE = PDMS. Apparent adsorption affinities are in the same order. In plasma, all surfaces except cellulose showed maxima in adsorption as a function of plasma concentration after 5 min contact. This is indicative of initial adsorption followed by displacement of fibrinogen (the Vroman effect). Cellulose showed very low adsorption of fibrinogen from plasma. The Vroman maxima were more pronounced on the tubing samples than on the films, and, as for the single protein experiments, adsorption was found to be less on tubing than on film samples. A tentative interpretation of the Vroman effect data suggests that the order of procoagulant activity of the materials may be: PDMS = PE < PVC < cellulose.