A novel route to prepare Fe3O4/P(MAA-co-NVP) cross-linked magnetic composite microspheres with core-shell architecture by surface-initiated radical dispersion polymerization.

A novel route was proposed to design and construct a magnetic composite microsphere with a controllable and regular core-shell architecture, which consists of Fe3O4 nanoparticles chemical-covalently encapsulated with pH-smart poly(methacrylic acid-co-N-vinyl pyrrolidone) (P(MAA-co-NVP)) cross-linked copolymers by a surface-initiated radical dispersion polymerization approach. The multistep surface treatment was employed to improve the dispersity and surface-chemical reactivity of Fe3O4 nanoparticles, involving introduction of active -NH2 groups, coupling of 1,1-methylene bis-(4-isocyanato-cyclohexane) and immobilizing of 2,2'-azobis[2-methyl-N-(2-hydroxyethyl) propionamide]. The structure and morphological characterization were carried out by FTIR, TEM, SEM and XRD etc. The neat Fe3O4 nanoparticles take on an aggregated spherical shape with an average diameter of about 12 nm, while Fe3O4/P(MAA-co-NVP) magnetic microspheres assume regularly monodispersed spheres with a mean dimension of ca. 0.8 microm. The dimension of the microspheres is abruptly increased with increasing pH values of the media. The microspheres exhibit superparamagnetic properties. It is expected that this type of novel microspheres can be employed as a magnetic targeted and pH-sensitive drug carrier.

Fabrication and caffeine release from Fe3O4/P(MAA-co-NVP) magnetic microspheres with controllable core-shell architecture.

A novel route was proposed to design and construct a magnetic composite microsphere consisting of Fe(3)O(4) nanoparticles chemically-covalently encapsulated with pH-smart poly(methacrylic acid-co-N-vinyl pyrrolidone) (P(MAA-co-NVP)) cross-linked co-polymers by a surface-initiated radical dispersion polymerization route. The multistep surface treatment was employed to improve the dispersity and surface-chemical reactivity of Fe(3)O(4) nanoparticles, involving introduction of active -NH(2) groups, coupling of 1,1-methylene bis-(4-isocyanato-cyclohexane) and immobilization of 2,2'-azobis[2-methyl-N-(2-hydroxyethyl) propionamide]. The structure and morphological characterization was carried out by FT-IR, TEM, SEM and XRD. The chemically covalent interactions were investigated by FT-IR, TEM, TGA and DSC. The neat Fe(3)O(4) nanoparticles took on an aggregated spherical shape with an average diameter of about 12 nm, while Fe(3)O(4)/P(MAA-co-NVP) magnetic microspheres assumed controllable and monodispersed spheres with a mean dimension of ca. 0.8 µm. The microspheres exhibited superparamagnetic properties. The in vitro caffeine release behavior under varying pH environment was investigated to evaluate the potential of Fe(3)O(4)/P(MAA-co-NVP) magnetic microspheres as a magnetic drug targeting carrier. The results indicated that the microspheres have a faster drug-release rate at pH 7.4 than at pH 1.4, corresponding to their pH swelling. The kinetic modeling demonstrated that the drug release is controlled by a balance between co-polymer chain relaxation and Fickian diffusion process, and the proposed carrier is suitable for a magnetic targeting drug-delivery system.