Reduction of protein adsorption on silica and polystyrene surfaces due to coating with Complex Coacervate Core Micelles

Abstract

The reduction of protein adsorption by a polymer brush formed upon adsorption of Complex Coacervate Core Micelles (C3Ms), consisting of a charged copolymer containing a neutral block and an oppositely charged homopolymer, on silica and polystyrene surfaces has been studied in situ using fixed angle optical reflectometry. Four proteins were used: lysozyme, β-lactoglobulin, bovine serum albumin, and fibrinogen. The C3M coating is responsive to changes in pH and salt concentration, and can be completely removed from the surface by rinsing with a concentrated salt solution (>2 M NaCl) or an acidic solution (pH < 2). The same surface can be subsequently coated with a fresh micellar layer. The reduction of protein adsorption by C3Ms was found to be influenced by the surface chemical composition, surface charge, hydrophobicity and salt concentration. C3M adsorption was higher on hydrophobic polystyrene than on hydrophilic silica, but stronger reduction of protein adsorption was observed on silica. The protein resistance of the brush is enhanced by increasing the salt concentration from 5 to 100 mM as a consequence of the stronger screening of excess charges. The stoichiometric charge composition, at which stable C3Ms are formed in bulk, is not the optimal one to create an effective coating on charged surfaces. On the silica surface higher reduction of protein adsorption was observed when micelles carry an excess charge opposite to the charge of the native surface.