Electrostatic adsorption of ferritin, proteins and nanoparticle conjugate onto the surface of polyelectrolyte multilayers

In this study, we quantitatively and kinetically analyzed the electrostatic adsorption of ferritin and apoferritin onto the surface of precursor films by using QCM, SEM and AFM. The precursor films were successively prepared by the alternate adsorption of poly(diallyldimethylammonium chloride) (PDDA) and poly(sodium 4-styrenesulfonate) (PSS) in the presence of suitable NaCl concentrations onto the QCM substrate. We observed their formation processes by frequency shifts of QCM. Furthermore, we also observed the adsorption of (apo) ferritin by an electrostatic interaction onto the outermost layer surface by QCM. The adsorption behavior of (apo) ferritin revealed the specific adsorption that (apo) ferritin only recognizes the surface of a precursor film depending on its surface charges in order to adsorb onto it. We also studied the effects of (apo) ferritin solution concentration, pH and washing/drying process on their adsorption behavior. This study on the immobilization of protein supramolecules will provide a method to build more complex functional inorganic nanostructures.