In this work, magnetite (Fe(3)O(4)) nanoparticles with an average size 10 nm modified by sodium oleate were prepared by the modified controlled chemical coprecipitation method, which can be well dispersed in water and linked well with protein molecules because of the presence of -COOH on their surface. Then magnetic poly(lactic acid) (PLA) and poly(lactic-co-glycolic acid) (PLGA) microspheres containing interferon alpha-2b (IFN-a-2b) were prepared by the modified water-in-oil-in-water solvent evaporation procedure. X-ray powder diffraction analysis, particle size analysis, transmission electron microscopy, scanning electron microscopy, and vibrating-sample magnetometer (VSM) analysis were carried out to examine phase composition, surface and interior morphology, size and size distribution, and magnetic properties of the magnetic microspheres. Also the effects of some important parameters on the magnetic biodegradable microspheres were investigated, such as magnetite dosage in the preparation system, stirring rate of the suspension medium, and concentration of the external aqueous phase. And the antiviral activity of IFN-a-2b encapsulated in the magnetic polymeric microspheres was evaluated by the vesicular stomatitis virus (VSV) cytopathicity inhibition assay. The results showed that the properties of IFN-loaded magnetic PLGA and PLA microspheres were better than the conventional protein-loaded polymeric microspheres, such as perfect magnetic properties, higher protein encapsulation efficiency, and less effect on the antiviral activity of protein. These indicated that the magnetic PLA and PLGA microspheres containing IFN-a-2b exhibited strong potential as targeted-drug delivery vehicles, which could be rapidly localized to the immunization-related tissues easily by an external magnetic field.
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