Tailoring Magnetic Microspheres with Controlled Porosity
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0969-W03-11
Tailoring Magnetic Microspheres with Controlled Porosity Muhammet S. Toprak1, Brandon J. McKenna1, Herb Waite1,2, and Galen D. Stucky1,3 1 Chemistry and Biochemistry, UC, Santa Barbara, CA, 93117 2 Department of Molecular, Cellular Developmental Biology, UC, Santa Barbara, CA, 93117 3 Materials Department, UC, Santa Barbara, CA, 93117
ABSTRACT The synthesis of organic and inorganic nano- and microspheres has attracted much interest for a variety of applications ranging from drug delivery to chemical storage and catalysis. We recently demonstrated the assembly of magnetic nanoparticles and polycations into hybrid microspheres in a single-step synthesis via complex coacervation. These microspheres showed viability for bio-applications as indicated by toxicity tests, and are therefore potential targeted drug delivery devices, as they can be directed magnetically. This work reports the recent progress on the potential use of these assemblies in drug release by controlling their porosity. Fluorescein tagged dextran molecules with different MW have been infiltrated into these entities to determine critical pore size by confocal fluorescence microscopy. Different physicochemical characterization results are also presented. INTRODUCTION Magnetic microspheres find widespread and diverse use in many fields, such as environment remediation (removal of toxic and radioactive waste solutions), with primary emphasis on biomedical applications, both therapeutic[1] (controlled drug targeting, [2] hyperthermia) and diagnostic (ELISA, NMR imaging, sensing).[3,4, 5] They have been used extensively in the field of biomagnetics, where they play important role in: biosensing,[6] isolation, and purification of biomolecules (enzymes, antibodies, peptides and nucleic acids), separation of biochemical products,[7] cells, bacteria and viruses from complex biological material,[8] cell labeling and sorting,[9] as well as in the determination of pathogens.[10] They are conventionally obtained by various techniques such as coating of magnetic particles by solvent evaporation, [11] precipitation of iron oxide on the polymer microspheres or heterogeneous polymerization methods including suspension,[12] dispersion[13] and emulsion[14] polymerization in the presence of colloidal iron oxide. The first composite magnetic core-shell microspheres were reported by Caruso et al. by the layer-by-layer (LBL) deposition method, for which the shell consists of magnetite nanoparticle/ polyelectrolyte multilayers and the colloidal core is polystyrene latex microspheres.[15] Critical parameters to control for such systems include shell permeability and mechanical stability for various applications. Möhwald et al. improved and tailored the properties of these polyelectrolyte microcapsules by glutaraldehyde cross-linking. [16]
For almost all applications listed above a stable, a bio-compatible surface is required to interact with biological systems. Furthermore, for drug delivery applications, it is important to control the porosity and permeability
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