Effect of surface hydrophobicity on the conformational changes of adsorbed fibrinogen

Abstract

The extent of conformational changes of fibrinogen adsorbed on germanium, poly(hydroxyethyl methacrylate) (poly(HEMA), Biomer, and polystyrene surfaces was studied using Fourier transform infrared spectroscopy (FTIR) coupled with attenuated total reflectance (ATR) optics. The contact angles of water on the solid surfaces were 19.3°, 35.5°, 37.6°, and 90.5°, respectively. The adsorption kinetics of fibrinogen from 1 mg/ml solution showed that the amount of adsorbed fibrinogen increased as the surface became more hydrophobic. The spectra of fibrinogen in the bulk solution and of fibrinogen tightly adsorbed on germanium, poly(HEMA), Biomer, and polystyrene surfaces were treated using Fourier self-deconvolution and the synthetic single-peak fitting techniques to resolve the overlapped peaks in the amide I and II regions. It was found that some α-helical structures were changed into the unordered structures and the content of β-turns was increased upon the protein adsorption. A weighted-peak shift method was used to examine the extent of the protein conformational changes upon adsorption on hydrophobic and hydrophilic surfaces. The results indicated that the adsorbed fibrinogen underwent a larger degree of conformational changes as the surface hydrophobicity increased.