Grafted ionomer complexes and their effect on protein adsorption on silica and polysulfone surfaces

We have studied the formation and the stability of ionomer complexes from grafted copolymers (GICs) in solution and the influence of GIC coatings on the adsorption of the proteins beta-lactoglobulin (beta-lac), bovine serum albumin (BSA), and lysozyme (Lsz) on silica and polysulfone. The GICs consist of the grafted copolymer PAA(28)-co-PAPEO(22) {poly(acrylic acid)-co-poly[acrylate methoxy poly(ethylene oxide)]} with negatively charged AA and neutral APEO groups, and the positively charged homopolymers: P2MVPI(43) [poly(N-methyl 2-vinyl pyridinium iodide)] and PAH center dot HCl(160) [poly(allylamine hydrochloride)]. In solution, these aggregates are characterized by means of dynamic and static light scattering. They appear to be assemblies with hydrodynamic radii of 8 nm (GIC-PAPEO(22)/P2MVPI(43)) and 22 nm (GIC-PAPEO(22)/PAH center dot HCl(160)), respectively. The GICs partly disintegrate in solution at salt concentrations above 10 mM NaCl. Adsorption of GICs and proteins has been studied with fixed angle optical reflectometry at salt concentrations ranging from 1 to 50 mM NaCl. Adsorption of GICs results in high density PEO side chains on the surface. Higher densities were obtained for GICs consisting of PAH center dot HCl(160) (1.6 divided by 1.9 chains/nm(2)) than of P2MVPI(43) (0.6 divided by 1.5 chains/nm(2)). Both GIC coatings strongly suppress adsorption of all proteins on silica (>90%); however, reduction of protein adsorption on polysulfone depends on the composition of the coating and the type of protein. We observed a moderate reduction of beta-lac and Lsz adsorption (>60%). Adsorption of BSA on the GIC-PAPEO(22)/ P2MVPI(43) coating is moderately reduced, but on the GIC-PAPEO(22)/ PAH center dot HCl(160) coating it is enhanced.