Biomedical coatings by the covalent immobilization of polysaccharides ontogas-plasma-activated polymer surfaces

As the surface properties of polymeric biomaterials play an important role in the performance: of biomedical devices, highly hydrophilic, ultrathin co atings were applied onto hydrophobic, perfluorinated and organosilicon poly mers by the covalent immobilization of polysaccharides using a reductive am ination reaction, Gas plasma (r.f. glow discharge) methods were employed to equip the surfaces of these normally unreactive polymeric substrates with chemical groups capable of reacting with polysaccharides in aqueous solutio n, in one variant, ammonia plasmas were used to introduce into the polymer surfaces a submonolayer of amine groups, Alternatively, an n-heptylamine pr ocess vapour was used to deposit a thin plasma polymer him that possessed s urface amine groups, The polysaccharides were activated for covalent immobi lization by periodate oxidation, which produced hemiacetal structures, as r evealed by NMR and XPS. The hemiacetal structures in the polysaccharide cha ins were reacted with the surface amine groups on the polymers. The resulti ng Schiff base linkages were stabilizers by reduction to secondary amine li nkages using sodium cyanoborohydride, Detailed surface analysis is importan t for verification that the intended chemistries have indeed been achieved in such multilayer coating schemes, X-ray photoelectron spectroscopy provid ed a thickness estimate of 1 +/- 0.3 nm for the polysaccharide coatings in the dehydrated state, Copyright (C) 2000 John Wiley & Sons, Ltd.