Structural and Magnetic Properties of Iron Oxide Nanoparticles in Shells of Hollow Microcapsules Designed for Biomedical Applications

The functional hollow biodegradable microcapsules modified with the maghemite gamma-Fe2O3 nanoparticles and the hollow spherical CoFe2O4/SiO2 nanocomposites were synthesized. Mossbauer spectroscopy data reveal that the main part maghemite nanoparticles have evident superparamagnetic behavior which is retained up to room temperature. This allows directing the microcapsules by an external magnetic field, which is very important for the problem of target drug delivery. On the other hand, the hollow spherical CoFe2O4/SiO2 nanocomposites with the small size particles do not show superparamagnetic behavior, but transit from magnetic to paramagnetic state by jump-like magnetic transition of the first order. This effect is a specific property of the magnetic nanoparticles isolated by an inert material. The method of synthesis can be modified with various bioligands on the silane surface, and such materials can have great prospects for use in diagnostics and bio-separation.