Construction of multilayer thin films containing avidin by a layer-by-layer deposition of avidin and poly(anion)s

A layer-by-layer deposition of avidin and poly(anion)s including poly(styrenesulfonate) (PSS), poly(vinyl sulfate) (PVS), and dextransulfate (DS) afforded multilayer thin films on the surface of a quartz slide, through electrostatic force of attraction between positive charges on the avidin molecule and negative charges on the polymer chains. It was possible to regulate the thickness of the films arbitrarily by changing the number of depositions. The loading of avidin in the multilayer thin films depended on the concentration of avidin and poly(anion)s in the bathing solutions from which the films were deposited. In the PVS- and PSS-based multilayer films, a large amount of avidin was immobilized in each deposition, depending on the concentrations of avidin and poly(anion) in the bathing solutions. In contrast, nearly a monomolecular layer was formed in each layer in the avidin-DS films independent of the concentration of bathing solutions. Avidin molecules assembled into the thin film retained its binding activity to biotin and analogues. The binding properties of avidin in the multilayer films were nearly comparable to those in solution; the films bound biotin, desthiobiotin, iminobiotin, and 2-(4′-hydroxyphenylazo)benzoic acid effectively.