ADSORPTION OF COMPLEMENT PROTEIN C3 AT POLYMER SURFACES

The adsorption of C3 at poly(methyl methacrylate) (PMMA) and poly( sty rene) (PS) surfaces was investigated with in situ ellipsometry and com pared to that at (hydrophilic and negatively charged) silica and (hydr ophobic) methylated silica, The adsorption of C3 at PMMA was higher th an that at PS, while the adsorbed layer thickness was the same for the two surfaces. For both PMMA and PS the adsorbed layer thickness (10 /- 2 nm) corresponds rather closely to that of end-on oriented C3 mole cules. The adsorption of C3 at PMMA and PS was found to be intermediat e between that at silica and methylated silica, although the adsorbed layer thickness was similar for all surfaces, The competitive adsorpti on among C3, human serum albumin (HSA), and factor B was investigated with ellipsometry and total internal reflection fluorescence spectrosc opy (TIRF). Addition of HSA after C3 preadsorption resulted in fractio nal C3 desorption for both PMMA and PS. Factor B deposition at PS afte r preadsorption of C3 and blocking with HSA was found to be largely du e to specific binding to C3/C3b, while in the case of PMMA, factor B w as largely accumulated through passive (displacement) adsorption. (C) 1996 Academic Press, Inc.