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.

Degradation behavior and biocompatibility of PEG/PANI-derived polyurethane co-polymers.

A series of polyurethane (PU) co-polymers with designable molecular weight between cross-linking dots was synthesized by a hydrogen transfer polymerization route from polyaniline (PANI), poly(ethylene glycol) (PEG), various curing agents and chain extenders using dibutyltin dilaurate as a catalyst. Their swelling, hydrophilicity, degradation and biocompatibility were inspected and assessed based on different degrees of polymerization of PANI and PEG, and their component proportion. Fourier transformation infrared spectrometry (FT-IR), (1)H-NMR spectroscopy, scanning electron microscopy (SEM), gel-permeation chromatography (GPC) and goniometry were used to characterize the structure and surface morphology of the synthesized PEG/PANI-based PU co-polymers, PU residues after degradation and degraded polymers at different time periods of hydrolysis. The thermal properties, aggregate structure and surface microstructure were examined by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and atomic force microscopy (AFM). Hemolysis, static platelet adhesion, dynamic clotting measurements and MTT assays were adopted to evaluate the hemo- or cytocompatibility. The experimental results indicated that these polymers exhibit various degrees of micro-phase separation, depending on the concentration and degree of polymerization of PANI, molecular weight of PEG, type of curing agent and chain extender, which further influence their swelling, hydrophilicity, degradable properties and biological performances in vitro. The incorporation of PANI and PANI* in co-polymers led to decreased thermal stability but slower decomposition rates than typical PEG-based PUs. The stress-strain tests showed that the as-prepared PU co-polymers possessed increased tensile strength and modulus, and decreased toughness in comparison with the blank PEG-based PU. These co-polymers are expected to find specific applications in tissue engineering or controlled drug release.