AVS 49th International Symposium
    Biomaterials Monday Sessions
       Session BI+VT-MoA

Paper BI+VT-MoA4
Protein Adsorption on Colloidal Oxide Particles

Monday, November 4, 2002, 3:00 pm, Room C-201

Session: Protein Surface Interactions
Presenter: K. Rezwan, ETH Zurich, Switzerland
Authors: K. Rezwan, ETH Zurich, Switzerland
L.P. Meier, ETH Zurich, Switzerland
M. Textor, ETH Zurich, Switzerland
L.J. Gauckler, ETH Zurich, Switzerland
Correspondent: Click to Email
Protein adsorption to surfaces of medical implants is an essential aspect of the cascade of biological reactions taking place at the interface between synthetic material and biological environment. The types and amounts of adsorbed proteins mediate subsequent adhesion, proliferation and differentiation of cells as well as deposition of mineral phases. Most metallic biomaterials are covered by a protective, stable oxide film such as titanium oxide on titanium. Hence proteins only interact with the oxide film and not with the underlying metal. Closer investigations of the protein - oxide interface are therefore of great relevance to the biomaterials field. In the past, protein adsorption and desorption has been investigated mostly on planar surfaces by in situ techniques such as ellipsometry, optical waveguide lightmode spectroscopy (OWLS) and quartz crystal microbalance (QCM). The drawback of these methods is the lack of direct information about surface charges, which are known to strongly affect protein adhesion and conformation at interfaces. We used colloid chemistry analysis methods such as colloidal vibration potential (CVP), X - ray disc centrifuge (XDC) measurements and UV – spectroscopy (UVS) to study in detail the adsorption of proteins to well-defined colloidal particles of typically 100 - 200 nm diameter. Combining these methods, the adsorbed amount of proteins and its influence on the zetapotential and the isoelectric point of the particles were determined with great precision and across a wide pH range. Adsorption of bovine serum albumin was found to alter the zetapotential of the oxides Al2O3, TiO2 and SiO2 and their isoelectric points to an extent that depended on the adsorbed mass. Combining UVS and XDC, the volume density and the thickness of the protein layer could be determined. The thickness corresponded to a monolayer or less. The adsorbed mass of albumin turned out to be nearly independent of pH in the range from pH 2 to 12.