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

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(<i>N</i>,<i>N</i>-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

Toward Anisotropic Hybrid Materials: Directional Crystallization of Amphiphilic Polyoxazoline-Based Triblock Terpolymers

We present the design and synthesis of a linear ABC triblock terpolymer for the bottom-up synthesis of anisotropic organic/inorganic hybrid materials: polyethylene-<i>block</i>-poly(2-(4-(<i>tert</i>-butoxycarbonyl)amino)butyl-2-oxazoline)-<i>block</i>-poly(2-<i>iso</i>-propyl-2-oxazoline) (PE-<i>b</i>-PBocAmOx-<i>b</i>-P<i>i</i>PrOx). The synthesis was realized <i>via</i> the covalent linkage of azide-functionalized polyethylene and alkyne functionalized poly(2-alkyl-2-oxazoline) (POx)-based diblock copolymers exploiting copper-catalyzed azide–alkyne cycloaddition (CuAAC) chemistry. After purification of the resulting triblock terpolymer, the middle block was deprotected, resulting in a primary amine in the side chain. In the next step, solution self-assembly into core–shell-corona micelles in aqueous solution was investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Subsequent directional crystallization of the corona-forming block, poly(2-<i>iso</i>-propyl-2-oxazoline), led to the formation of anisotropic superstructures as demonstrated by electron microscopy (SEM and TEM). We present hypotheses concerning the aggregation mechanism as well as first promising results regarding the selective loading of individual domains within such anisotropic nanostructures with metal nanoparticles (Au, Fe₃O₄)