The major goal of this project is to explore two types of dispersed composite nanomaterials collectively called the block ionomers complexes or BIC. The first materials are synthesized by reacting dual hydrophilic block copolymers, containing ionic and water soluble nonionic segments, with oppositely charged polyions. Such materials form micelle-like aggregates with the polyion complex core and hydrophilic nonionic corona in aqueous media. The second materials are obtained by reacting micelles from block copolymers, containing ionic and water insoluble nonionic segments with the polyions of opposite charge. Such materials contain the micelles with hydrophobic cores as nucleating particles surrounded by insoluble polyion complex layer and a charged hydrophilic corona from the polyion present in excess. The area of BIC has emerged a decade ago as a result of intersection of the studies on the selfassembly of polyelectrolyte complexes and ionic block copolymers in selective solvents. Several promising applications of BIC materials have been determined, including the delivery of DNA, therapeutic proteins, low molecular mass drugs and imaging agents. One fundamental property of regular polyelectrolyte complexes is the ability to participate in highly cooperative polyion interchange reactions with other polyelectrolyte components present in solution. Initial studies suggest that such reactions involving BIC can also proceed. Although these reactions are of great importance for the self-assembly and practical use of BIC no systematic studies in this area have been conducted. This proposal will address this deficiency using fluorescence technique to determine rates and directions of these reactions and understand the contribution of the core-shell architecture of BIC to their dynamic properties. Novel materials will be synthesized and characterized, such as BIC obtained by reacting polyelectrolyte micelles having cross-linked ionic cores and nonionic water soluble corona or micelles having hydrophobic cores and polyion corona with various polyions, including DNA and proteins. The stability, size, charge and morphology of the BIC will be determined using a combination of physicochemical methods. In particular, the proposal will employ for characterization of BIC the Atomic Force Microscopy to determine the particle topography and Small Angle Neutron Scattering to determine the particle internal structure. A theoretical analysis of the BIC will be carried out in collaboration with scientists at Moscow State University. Overall the proposal will greatly advance experimental and theoretical understanding of BIC and develop new classes of BIC materials that can be useful in biomedical applications. The proposal will have broader impact by creating a favorable environment for collaboration between the material and biomedical scientists and will contribute to interdisciplinary training of students and scientists in the University of Nebraska and beyond. The results of the studies will be disseminated through scientific meetings and seminars within the Center for Drug Delivery and Nanomedicine, which will advance applications of polymer nanomaterials in drug and gene delivery. The integration of research and education will benefit from the course on Polymer Therapeutics taught by the PI and Co-PI, which incorporates recent scientific findings. The dissemination will be enhanced by the active use of Internet, such as online posting of the course and lectures. The scientific and technological understanding in the State of Nebraska will be enhanced by presentations to broad community groups such as MiniMedical School. These synergistic activities will demonstrate linkage between scientific discoveries and societal benefit by providing the examples of application of polymer materials including the new findings anticipated from this project.
