Preparation And Application Of Magnetic Polymer Microspheres

Magnetic polymer microspheres are a kind of novel functional materials, which exhibit excellent applications in biomedical fields including tumor target therapy, bioseparation, magnetic resonance imaging and so on. The work presented here focus on preparing magnetic polymer microspheres in two different ways including emulsifier-free emulsion polymerization and self-assembly of fluorine-containing amphiphilic copolymers with nanoparticles method, the details are as follows:(1) Emulsifier-free emulsion polymerization invokes more interest in bioapplication because this method without initially adding surfactants can avoid cytotoxic and antibacterial effects of the emulsifier. As a result, magnetic microspheres were prepared by emulsifier-free emulsion polymerization of styrene, n-butyl acrylate (BA),[2-(methacryoyloxy ethyl] trimethylammonium chloride (DMC) with oleic-acid modified Fe3O4nanoparticles, using divinylbenzene as crosslinker. The obtained particles were characterized by FT-IR,XRD, TEM, VSM methods, the results show that Fe3O4nanoparticles were well encapsulated by the polymers and the particle size is around300nm with the saturation magnetization of7.69emu/g. Electrostatic interaction between cationic microspheres and DNA were confirmed by Zeta potential, PCS, UV-Vis spectroscopy, fluorenscence spectroscopy and agrose gel electrophoresis methods. The results show that the obtained cationic magnetic microspheres have potential application in magntic-target DNA delivery and separation.(2) The magnetic microspheres were obtained by self-assembly of fluorine-containing amphiphilic poly(HFMA-g-PEGMA) copolymers with oleic acid modified Fe3O4nanoparticles in an aqueous medium. The amphiphilic poly(HFMA-g-PEGMA) copolymers were first synthesized with hydrophobic monomer hexafluorobutyl methacrylate and hydrophiphilic monomer poly(ethylene glycol) methacrylate. The structure and properties of amphiphilic copolymers were firstly characterized by FTIR、1H-NMR,19F-NMR, surface intension method and GPC. The oleic acid modified Fe3O4nanoparticles form small clusters in the poly(HFMA-g-PEGMA) micelles with a mean diameter of100nm and the magnetomicelles show high stability in an aqueous medium due to the high hydrophobic fluorine segments in graft copolymers enhance the stability of the micelles. The magnetomicelles also show good cytocompatibility based on the MTT cytotoxicity assay and possess paramagnetic properties with saturation magnetization of17.14emu/g. Their good stability, cytocompatibility, and paramagnetic properties render the materials attractive in drug delivery and in vivo magnetic resonance imaging (MRI) applications. The magnetomicelles exhibit high efficiency as a negative MRI agent in T2-weighted imaging. In vivo MRI studies demonstrate that the contrast between liver and spleen is enhanced by the magnetomicelles. These favorable properties suggest clinical use as contrast agents in MRI.