Adsorption of Fibrinogen on Titanium and Gold Surfaces Studied by ESCA and Ellipsometry

Abstract

The interaction of proteins with nonbiological surfaces is important because of its possible involvement in the biological acceptance or rejection of artificial implants. In this paper, we report on the adsorption of fibrinogen onto titanium and gold metal surfaces. Results both from X-ray photoelectron spectroscopy (ESCA) studies performed in high vacuum and from ellipsometric measurements performed with the protein layer in buffer solutions are reported. Both techniques show that there is a difference in the adsorption behavior and the conformation of the protein on titanium and gold surfaces, respectively. While the fibrinogen adsorbs in more or less a native form on the titanium surface, it changes its conformation and adsorbs in a thin dense layer on the gold surface. The comparison between the ESCA and the ellipsometry measurements shows a relative change in the conformation of the protein molecules on the titanium surface due to dehydration during high vacuum conditions. Despite this, the protein molecules on the titanium surface seem to retain much of their structure also under UHV conditions. This was concluded by comparing mainly the shape of the C 1 s peak with that from thick bulk protein layers. The results obtained are discussed in terms of electrostatic and hydrophobic interactions during the adsorption processes.