ADSORPTION OF POLY(ETHYLENE GLYCOL) AMPHIPHILES TO FORM COATINGS WHICH INHIBIT PROTEIN ADSORPTION

The adsorption of poly(ethylene glycol) (PEG)-esterified fatty acids a t methylated silica, phosphatidic acid, and phosphatidylcholine surfac es was investigated with in situ ellipsometry. For a series of PEG-fat ty acid esters of ethoxy groups and acyl tails of type C-i:j-EO(151) ( 16 less than or equal to i less than or equal to 18, 0 less than or eq ual to j less than or equal to 2)adsorption at methylated silica was i ndependent of bulk micellization, and a plateau was reached below the critical micellization concentration (CMC). The plateau adsorbed amoun t for the investigated fatty acid esters was only weakly dependent on the nature of the hydrophobic moiety. Instead, saturation adsorption w as largely determined by the interactions between PEG chains. Adsorpti on isotherms were therefore essentially identical on all three of the quite different surfaces. At saturation adsorption, the adsorbed layer thickness was 10-15 nm, while the average adsorbed layer concentratio n was 0.07 g/cm(3). Formation of the PEG-surfactant coatings thus appe ared to involve significant molecular alterations of PEG from a random coil, The ability of the PEG-ester coatings to inhibit protein adsorp tion was also investigated. At the adsorption plateau, all coatings in vestigated displayed quite good ability to inhibit adsorption by a num ber of serum proteins. For the surfaces studied this ability decreased below 0.2 CMC. These findings are discussed in relation to the abilit y of PEG-derivatized lipids to control the in vivo fate of colloidal d rug carriers. (C) Academic Press, Inc.