ABSTRACT
In order to evaluate the respective influence of surface nanotopography and chemical composition on blood compatibility, plasma protein adsorption (fibrinogen - Fg and albumin - HSA, quantified simultaneously by dual radioassays) and platelet adhesion were investigated on a range of materials. Reference surfaces were glass, polystyrene and poly(vinyl chloride), as well as pieces of commercial blood bags. Colloidal lithography with 65 and 470 nm polystyrene latex particles was used to prepare nanostructured surfaces with either one layer of colloids or with bimodal roughness. The surfaces were further conditioned by adsorption of poly(ethylene oxide) (PEO)-containing compounds (Pluronic F 68 and PLL-g-PEG). Study of the simultaneous adsorption of Fg and HSA on reference substrates demonstrated that the Fg/HSA adsorbed amount ratio decreases as the substrate hydrophobicity increases, the lower ratio being obtained with commercial blood bag. This is due to the higher resistance of HSA adsorbed on hydrophobic substrates to displacement by proteins from the solution. Such higher resistance was also shown to occur in the case of displacement by constituents of non-diluted blood plasma. Nanostructured substrates gave about the same Fg/HSA ratio as polystyrene and poly(vinyl chloride). Surface conditioning with Pluronic F 68 reduced the adsorption of Fg in competition with HSA on all substrates except glass, while PLL-g-PEG decreased the adsorbed amount of both Fg and HSA on glass but not on the other substrates. Positive correlations between the amount of adhering blood platelets and both the Fg/HSA ratio and the absolute amount of Fg adsorbed in competition with HSA were found for all substrates (reference and nanostructured, as such or after PEO conditioning, except native glass which had to be discarded due to the formation of clots in the liquid phase). These quantities were also related to the state of activation of adhering platelets. This supports the concept that blood compatibility of materials is primarily governed by the presence of Fg in the adsorbed phase, as a result of the competition with other plasma proteins. This is in turn strongly influenced by surface hydrophobicity. Surface nanostructuration as performed here (relief in the range of 50-500 nm) did not affect significantly the relationship between Fg adsorption and platelet adhesion.
