ADSORPTION BEHAVIOR OF AMPHIPHILIC POLYMERS AT HYDROPHOBIC SURFACES -EFFECTS ON PROTEIN ADSORPTION

The adsorption of four different amphiphilic polymers to a model surfa ce has been studied, and the effects of the adsorbed amphiphiles on th e subsequent adsorption of fibrinogen (Fg) and human serum albumin (HS A) at the surfaces were investigated. The amphiphilic polymers were on e commercially available ABA block copolymer, Pluronic PE9400 (PE94), composed of poly(ethylene oxide) (A-blocks) and poly(propylene oxide) (B-block), and three graft copolymers, two with backbones of poly(styr ene-co-acrylamide) (STY) and one with a backbone of poly(methyl methac rylate-co-ethylhexyl methacrylate) (ACRY). The backbones carried poly( ethylene oxide) (PEG) grafts, The model surface was a hydrophobic meth ylated silica surface (HMS). The amphiphilic polymers were adsorbed at the HMS surface from an ethanol/water solution. The adsorption proces s was monitored by ellipsometry. After rinsing with phosphate buffered saline (PBS), protein was added and the continued adsorption measured by ellipsometry. Surfaces modified by adsorption of the amphiphilic p olymers were also characterized by contact angle measurements and X-ra y photoelectron spectroscopy (XPS). According to these measurements th e amphiphilic polymers adsorbed in significant amounts at the HMS surf ace. A limited study by atomic force microscopy (AFM), as well as the XPS measurements, suggests that both single molecules and micellar agg regates adsorb at the surface. ACRY and PE94 gave the highest levels o f adsorption. As compared to the Pluronic block copolymer the graft co polymers were more strongly attached to the HMS surface, as shown by l ess desorption on rinsing with solvent. The ellipsometric results show that the adsorption of HSA and Fg at HMS surfaces containing preadsor bed amphiphilic polymer was significantly reduced as compared to the b are HMS surface. ACRY and PE94 showed the largest effects. Both polyme rs gave more than a 20-fold reduction of the Fg adsorption and a 10-fo ld reduction of the HSA adsorption. The STY polymers reduced the prote in adsorption by a factor of 2-3. (C) 1996 Elsevier Science Limited