Adsorption of human albumin and fibrinogen onto heparin-like materials II. Desorption and exchange processes

Abstract

The dynamic properties characterizing the interactions of adsorbed fibrinogen and albumin layers with three adsorbent surfaces have been examined using a method previously described (J.C. Voegel et al., Colloids and Surfaces, 10 (1984) 9–19). Solid surfaces were those of bare glass beads, glass beads covered with a strongly adsorbed polystyrene-sulfonate/poly(2-vinylpyridine) block copolymer and chemically modified polystyrene beads; the beads were packed into a minicolumn. As a general rule, the observed desorption or exchange processes are slow (relaxation times of the order of hours) and the extent of protein removal from the surface is higher in exchange experiments. On the time scale of our observations, two populations were identified in the adsorbed protein layer: exchangeable (or desorbable) and non-exchangeable adsorbed molecules. The extent of desorption or exchange is less important for fibrinogen than for albumin, which correlates well with the equilibrium studies of Part I (pp. 271–288). However, albumin desorption is very low on the surfaces containing sulfamide—glutamic acid groups. Finally, it is shown by radioactive labeling that the exchange process corresponds to a turnover between surface and solution molecules.