Application of quartz crystal microbalance to study the impact of pH and ionic strength on protein–silicone oil interactions

In this study, we have used quartz crystal microbalance (QCM) to quantitate the adsorption of a protein on silicone oil coated surfaces as a function of protein concentration, pH and ionic strength using a 5 MHz quartz crystal. Protein adsorption isotherms were generated at different solution pH and ionic strengths. Surface saturation concentrations were selected from adsorption isotherms and used to generate adsorption profiles from pH 3.0 to 9.0, and at ionic strengths of 10 mM and 150 mM. At low ionic strength (10 mM) and pH 5.0 (close to the isoelectric point of the protein), maximum adsorption of protein to the silicone oil surface was observed. At higher ionic strength (150 mM), no significant pH influence on adsorption was observed. QCM could be used as a reliable technique to study the binding of proteins to silicone oil coated surfaces.

Graphical abstractThe effect of solution pH and ionic strength on the interactions between a model protein and silicone oil was investigated using quartz crystal microbalance. At low ionic strength, electrostatic forces mainly govern the adsorption of protein to the silicone oil/water interface while at higher ionic strength, hydrophobic interactions dominate the overall protein adsorption.Figure optionsDownload full-size imageDownload as PowerPoint slide