Plasma protein interactions with Pluronic(TM)-treated colloids

Hydrophobic polystyrene colloids are known to rapidly take up numerous proteins from solution, including the key plasma proteins albumin and fibrinogen. However, when coated with poly(ethylene oxide) (PEO)-containing block copolymers these particles become much less prone to protein adsorption. The noted protein repulsion is thought to be influenced by three important factors: the surface concentration of the adsorbed polymers, the thickness of the adsorbed layer and the surface mobility of the polymer chains. At a given surface concentration, the increase in both thickness and dynamics is directly correlated with a decrease in protein adsorption, as seen from the interactions of selected copolymer adsorption complexes with human fibrinogen. The significant suppression of fibrinogen adsorption to polystyrene (PS) colloids coated with Pluronic(TM) F108, which has the highest molecular weight and longest PEO chains among the studied block copolymers, prompted a detailed examination of the interaction of such surfactant-treated particulate surfaces with other proteins. Exposure of the coated particles to whole plasma gives rise to a certain polymer displacement with concomitant uptake of a limited amount of protein. This uptake does not result in aggregation nor does it add to the size of each particle. Rather, as shown in a companion study, the repulsion layer established by the stable F108 coating appears to be correlated with the prolonged blood circulation of such coated PS colloids.