Reversible Electrostatic Adsorption of Polyelectrolytes and Bovine Serum Albumin onto Polyzwitterion-Coated Magnetic Multicore Nanoparticles: Implications for Sensing and Drug Delivery

Abstract

We herein present the reversible formation of hybrid nanoparticles featuring a magnetic core and two consecutive polyzwitterion/polyelectrolyte (or protein) layers. Starting from multicore iron oxide nanoparticles, a first coating with zwitterionic poly(dehydroalanine) is realized, and the resulting PDha@MCNP [PDha = poly(dehydroalanine) and MCNP = multicore nanoparticle] shows pH-dependent (invertible) surface charge and dispersion stability. In a second step, this can be used as a versatile platform to adsorb either polycations {[poly(N,N-dimethylamino)ethyl methacrylate] (PDMAEMA) or poly(aminomethyl acrylate)}, a polyanion [poly(styrenesulfonic acid) (PSS)], or a model protein in a quasi layer-by-layer approach. The size, surface charge, and aggregation behavior of the resulting double-layer-coated particles are investigated via dynamic light scattering, transmission electron microscopy, ζ-potential, and turbidity measurements. In contrast to typical layer-by-layer coatings, the use of polyzwitterionic PDha as the first layer allows the pH-dependent release of the second polyelectrolyte shell (PDMAEMA and PSS) upon charge inversion. This turns such reversible multilayer coatings into interesting candidates for applications where controlled swelling or release is in focus and where it is important to control which part of a segmented or nanostructured system responds to changes in the surrounding medium.