Competitive protein adsorption at radio frequency plasma polymer surfaces

Abstract

The competitive adsorption of human serum ablumin (HSA), IgG and fibrinogen (Fgn) at radio frequency plasma polymer surfaces was studied with in situ ellipsometry and TIRF (total internal reflection fluorescence spectroscopy). While both IgG and Fgn adsorbed preferentially over HSA at hydrophobic surfaces, such as P-HMDSO (monomer: hexamethyldisiloxane), preadsorption of the latter protein dramatically reduced the adsorption of the two former. Furthermore, the preadsorbed HSA is not exchanged by HSA added after preadsorption, i.e., the HSA “blocking” is due to an irreversible adsorption of this protein, presumably involving conformational changes of HSA on adsorption. Different plasma polymer surfaces behave differently regarding competitive protein adsorption. For example, at P-HMDSO, the adsorption from all mixtures investigated is substantial. Furthermore, HSA and IgG dominate the adsorption from a ternary mixture corresponding to 1/100 plasma, although Fgn is still present at the surface. At P-AA (monomer: acrylic acid), on the other hand, the adsorption is lower, except for the IgG/Fgn binary mixture, and Fgn and HSA dominate the adsorption from a ternary mixture corresponding to 1/100 plasma, while IgG is depleted from the surface.