Characterization of protein films on dental materials: Bicinchoninic acid assay (BCA) studies on loosely and firmly adsorbed protein layers

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.