Adsorption of hydrophobized IgG and gelatin onto phosphatidyl choline-coated silica

Covalent modification of human IgG and gelatin (type A) by fatty acid esters (C₈, C₁₂ and C₁₆) of N-hydroxysuccinimide was carried out. Preparations of hydrophobized IgG containing 9 and 25 attached caprylic and 25 palmitic chains and preparations of gelatin with low and high degree of modification were obtained. The adsorption of unmodified and modified proteins at a hydrophobic surface obtained by coating silica with a phosphatidyl choline monolayer was studied. It was found that an increase in the proteins' hydrophobicity leads to an increase in their adsorption determining by hydrophobic binding which overcomes the electrostatic repulsion between the negatively charged surface and the negatively charged protein molecules. An increase in the IgG hydrophobicity also resulted in the formation of a more compact monolayer. An increase in gelatin adsorption after its hydrophobization led to either the formation of a more compact monolayer or the formation of a more condensed molecular configuration after attachment of alkyl chains. For both proteins the adsorption can be accompanied by penetration of these chains into the phospholipid monolayer. Copyright (C) 1999 Elsevier Science B.V.