Electrostatically assembled polyelectrolyte/dendrimer multilayer films as ultrathin nanoreservoirs

We report the preparation of loadable ultrathin, multilayered polyelectrolyte/dendrimer films by the sequential electrostatic deposition of negatively charged poly(styrenesulfonate) (PSS) and a positively charged fourth generation poly(amidoamine) dendrimer (4G PAMAM). Multilayers were first constructed on planar supports to examine their layer-by-layer growth. Quartz crystal microbalance (QCM) measurements showed regular growth for each layer deposited, while UV-vis spectrophotometry revealed an adsorption-desorption trend to film formation, with partial PSS removal upon deposition of 4G PAMAM. PSS/4G PAMAM films were subsequently constructed on spherical latex colloids. Fluorescence spectroscopy showed that the films, when exposed to dye-containing solutions, acted as nanoreservoirs, sequestering the charged molecules from solution due to the presence of the oppositely charged dendrimer. Release of the entrapped dye molecules was subsequently achieved by concentration-dependent diffusion in isotonic saline solutions, illustrating the potential of the dendrimer-based films as systems for the uptake and release of various compounds.