The superparamagnetic multilayer hybrid hollow microspheres have been fabricated using the layer-by-layer assembly technique by the electrostatic interaction between the polyelectrolyte cation chitosan (CS) and the hybrid anion citrate modified ferroferric oxide nanoparticles (Fe 3 O 4 -CA) onto the sacrificial polystyrene sulfonate microspheres templates after etching the templates by dialysis. The saturation magnetization and magnetite contents of the superparamagnetic multilayer hybrid hollow microspheres were 32.46 emu/g and 51.3%, respectively. The hybrid hollow microspheres showed pH-sensitive characteristics. The adsorption and release of the basic dye (methylene blue) were applied to investigate the interaction between the amino groups of CS and the carboxyl groups of the Fe 3 O 4 -CA nanoparticles in different pH media. The superparamagnetic pH-sensitive multilayer hybrid hollow microspheres are expected to be used for the targeted controlled release of drugs or in diagnostics. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3135-3144, 2010 KEYWORDS: hybrid hollow microspheres; layer-by-layer assembly; pH sensitive; superparamagnetic; targeted controlled releaseRecently, surface-charged nanoparticles have been used for the fabrication of the multilayer hybrid hollow microspheres.

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Novel magnetic‐targeted pH‐responsive drug delivery system have been designed by the layer‐by‐layer self‐ assembly of the polyelectrolytes (oligochitosan as the polycation and sodium alginate as the polyanion) via the electrostatic interaction with the oil‐in‐water type hybrid emulsion droplets containing the superparamagnetic ferroferric oxide nanoparticles and drug molecules [dipyridamole (DIP)] as cores. Here the drug molecules were directly encapsulated into the interior of droplets without etching the templates and refilling with the desired guest molecules. The drug‐delivery system showed high encapsulation efficiency of drugs and drug‐loading capacity. The cumulative release ratio of dipyridamole from the oligochitosan/sodium alginate multilayer‐encapsulated magnetic hybrid emulsion droplets (DIP/Fe3O4‐OA/OA)@(OCS/SAL)4 was up to almost 100% after 31 h at pH 1.8. However, the cumulative release ratio was only 3.3% at pH 7.4 even after 48 h. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

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