Calcium uptake by casein embedded in polyelectrolyte multilayer

The aim of our work was to investigate formation of polyelectrolyte multilayer films containing α- and β-casein. Since in neutral pH casein is negatively charged (as verified by electrophoretic mobility measurements) it has been used as a polyanionic layer for the film build-up. Casein containing films were formed on Si/SiO2 wafers. The formation of the film was investigated by liquid cell ellipsometry. After the multilayer films were formed they were contacted with solution containing calcium ions and changes in the film thickness were monitored. Additionally the surfaces of casein containing multilayers were analyzed with AFM for the structural changes within the films occurring after binding of calcium ions. Presence of calcium ions bound in the film was also monitored by XPS. We concluded that casein embedded in the polyelectrolyte multilayers preserves its ability to bind calcium ions.