Search

For a better understanding of biofilm establishment, adhesion forces of proteins on immobilized protein layers were investigated by scanning force spectroscopy (SFS). For this purpose the experimental setup to immobilize protein layers on the surface is important. The influence of the method chosen to immobilize the proteins on the surface was examined and afterwards the effect of variations in pH and contact time on the measured adhesion forces in protein-protein interaction was analyzed. The adsorption of bovine serum albumin (BSA) on BSA-coated silicon was used here as a model system. To coat the substrate, free adsorption, crosslinking with glutaraldehyde, and covalent protein binding to the surface after silanization were used. For the latter different deposition methods of the silane were compared. Depending on the immobilization method the measured protein-protein interactions show distinct differences. Covalent attachment of proteins is a promising approach to attain stable, pre-adsorbed protein layers for SFS measurements. The adhesion forces of a BSA-coated cantilever on such layers seem to be dominated by electrostatic interactions of the molecules. [ABSTRACT FROM AUTHOR]

Glass is one of the most important materials in medical packaging. Protein adsorption at the glass walls leads to loss of the active substance in the glass vials and thus to high costs for the pharmaceutical industry, in particular in the case of expensive drugs. Thus more knowledge about the basic mechanisms and the involved parameters in protein interaction with glass surfaces is desirable. In this context, the adsorption of bovine serum albumin (BSA), fibrinogen (FIB), and lysozyme (LYS) on typical glass surfaces (borosilicate glass, quartz glass) was investigated by dynamic contact angle (DCA) measurements as a function of pH value. DCA allows the determination of the relative amount of adsorbed protein and of the reversibility of the adsorption process. It will be shown that the amount of adsorbed protein is governed by electrostatics on quartz glass while on borosilicate glass no influence of the pH value (and hence the electrostatics) can be seen. This can be explained by the different surface composition which has apparently an important influence on the adsorption process. In addition it could be determined that on both glass surfaces, none of the investigated proteins shows a complete reversibility of the adsorption process, i.e., desorption is never complete. In conclusion the interaction with glass surfaces cannot be generalized but electrostatics play a major role and thus the interaction of proteins with glass surfaces may be changed by shifting the pH value of the solutions or the isoelectric point (IEP) of the surfaces. [ABSTRACT FROM AUTHOR]

The loosely and firmly adsorbed amount of bovine serum albumin (BSA) on dental titanium and dental gold was investigated by bicinchoninic acid assay (BCA assay). This method does not require special properties of the sample like a high reflectivity or conductivity and turns the BCA assay into a valuable tool to investigate a widespread spectrum of different substrate materials, e.g., natural enamel. The experiments in this work showed that it is possible to distinguish between loosely and firmly bound protein with the BCA assay. On the here investigated dental titanium and dental gold samples the amount of adsorbed BSA was dominated by the loosely bound part. On dental gold the total amount of adsorbed BSA was significantly higher than on titanium. The amount of loosely bound BSA was high near the isoelectric points of dental titanium and dental gold while the amount of firmly adsorbed BSA on dental titanium followed the electrostatics. At high pH values (pH 9.0) conformational changes of the BSA molecules played a key role in the adsorption process. [ABSTRACT FROM AUTHOR]