Competitive adsorption of lysozyme and non-ionic surfactants (Brij-35 and pluronic P123) from a mixed solution at water-air and water-xylene interfaces

The adsorption of lysozyme in the presence of high molecular weight (pluronic P123) and low molecular weight (Brij-35) non-ionic surfactants was studied at liquid-liquid and liquid-air interfaces. Using tritium-labeled compounds and liquid scintillation spectrometry of tritium, we investigated the competitive adsorption of lysozyme-pluronic P123 and lysozyme-Brij-35 at the aqueous-xylene interface. The substitution of protein by both polymer and low molecular weight surfactant was observed, while the presence of lysozyme does not influence the behavior of non-ionic molecules. We found that the ionic strength of the aqueous phase does not influence the strength of the effect, while it has a significant influence on the rate of diffusion and penetration of the adsorption layer by free protein. The thermodynamics of the competitive adsorption was described by the model suggested by Fainerman and co-authors, and the obtained parameters were used to describe the interfacial tension isotherms of the respective mixtures at the aqueous-air interface. Thus, the adsorption of each component of the mixture (protein and non-ionic surfactant) at the aqueous-air interface was revealed.