XPS studies on the organization of adsorbed protein films on fluoropolymers

Abstract

The adsorption of proteins to the surfaces of materials influences a number of biological interactions including cell adhesion and thrombus formation. Although the amount, composition, and kinetics of deposition of protein films on surfaces have been thoroughly explored, there have been relatively few studies on the organization of protein films on surfaces. This work describes the application of X-ray photoelectron spectroscopy (XPS) to study the structure and organization of adsorbed hemoglobin and fibronectin films on poly(vinyl fluoride), poly(vinylidene fluoride), and poly(tetrafluoroethylene). A model based upon the Beer-Lambert relationship, modified to consider fractional coverage, was used to calculate angular-dependent signal intensities which could then be compared with experimental data. The data, when compared with the model, suggested that bare areas of polymer exist after adsorption (i.e., the protein film is in “islands”) and the degree of coverage of the polymer surface increases with increasing polymer critical surface tension. The fibronectin was found to cover a larger fraction of each polymer surface than hemoglobin.