IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Biomaterials Monday Sessions
       Session BI+SS-MoA

Paper BI+SS-MoA8
The Water Content of Proteins during Adsorption

Monday, October 29, 2001, 4:20 pm, Room 102

Session: Role of Water in Biological Systems
Presenter: J. Voros, ETH-Zurich, Switzerland
Authors: J. Voros, ETH-Zurich, Switzerland
M. Textor, ETH-Zurich, Switzerland
N.D. Spencer, ETH-Zurich, Switzerland
Correspondent: Click to Email
Adsorption of proteins at solid-liquid interfaces is a process of central importance for biosensors and biomaterials. The role of water is a key issue in this process. The use of two biosensor techniques and identical experimental conditions have made it possible to follow the evolution of the water content of proteins during the surface adsorption-relaxation process.@footnote 1@ Optical waveguide lightmode spectroscopy (OWLS) involves the incoupling of a laser into a planar waveguide generating an evanescent field. The measurement of the incoupling angles allows for the online monitoring of the dry mass of surface-adsorbed macromolecules. Quartz crystal microbalance with dissipation factor (QCM-D) is a technique for monitoring the mass of adsorbed molecules via changes in the resonant frequency, f, while also getting information about the viscoelasticity of the layer by measuring the dissipation factor, D. The f-shift of the QCM-D is due to the change in total coupled mass, including the water coupled to the layer. The amount of water in an adsorbed adlayer can thus be determined by subtracting the adsorbed mass value obtained by OWLS from the value measured by the QCM-D in experiments carried out under identical conditions. The water content of the protein layer was found to be characteristic for different proteins and to change during the adsorption process. The time evolution of the water content provides information on the conformational changes during the adsorption. The dissipation factor measured by the QCM-D correlates well with the amount of water present in the adsorbed protein layer. Several blood proteins were measured on hydrophilic (TiO@sub 2@) and on hydrophobic surfaces. Dependence on the protein concentration and on the ionic strength of the buffer was also examined. @FootnoteText@ @footnote 1@ F. Hook, J. Voros, M. Rodahl, R. Kurrat, P. Boni, J.J. Ramsden, M. Textor, N.D. Spencer, P. Tengvall, J. Gold, B. Kasemo, Colloids and Surfaces B: submitted, 2000.