| Magnetic polymer microsphere is a kind of hybrid microsphere with magnetic, which is composed of polymer and inorganic magnetic particles. Magnetic composite materials not only possess the unique characters of magnetic materials such as superparamagnetism but also the properties of the polymer. At the same time, the hollow structure makes them have large surface area, small density, large internal space and good surface permeability etc. Therefore, the materials have potential applications in biomedicine, catalysis, sewage treatment etc. Based on the research background and the development prospect, we modified the magnetic hollow particles, via coated carboxymethyl chitosan (CMCS) to develop the biocompatibility and the dispersibility in the aqueous solution.The research emphasis of this paper is on exploring the synthesis of magnetic hollow composite materials, studying their properties and modifying them to obtain multiple functional properties. Magnetic hollow composite materials have been applied in drug release and enzyme immobilization. Four points o f this paper are as follows:1. The hollow Fe3O4/SiO2microspheres were prepared using the template-based method. The procedure as follow:The polystyrene microspheres were prepared using emulsifier-free polymerization, PS/Fe3O4composite microspheres were prepared using the co-precipitation method, and then the PS/Fe3O4/SiO2microspheres were prepared by the sol-gel method. Finally, the hollow Fe3O4/SiO2nanoparticles were prepared through calcinations of PS microspheres. The composite particles were charact-erized by TEM、FT-IR and VSM. The results showed that the microspheres had an average size of400nm. The fabricated material is thus proposed as a biological material for optical sensing and protein delivery.2. The hollow Fe3O4/SiO2(HMS) nanoparticles treated with3-aminopropyltrietho-xysilane (APTES) by silanization reaction,-OH on the surface of HMS microsphere was replaced by-NH2of the amino silane coupling agent. The activation to the-COOH on the surface of CMCS was conducted by the condensing and activator activating reagent. Then the hollow Fe3O4/SiO2@CMCS (HMS-CMCS) magnetic polymer microspheres were prepared via the reaction between-NH2and-COOH. The obtained nanoparticles were characterized by TEM, FT-IR and VSM, the results showed that the microspheres had an average size of420nm. After freeze drying the walls of the HMS-CMCS microspheres had numerous micropores with a broad distribution of approximately1-5nm. The magnetic polymer microspheres had good distribution in aqueous solution, and exhibited good magnetic response.3. In vitro controlled release examination based on cisplatin (CDDP) as the model drug and HMS microspheres and HMS-CMCS microspheres as the carriers, we researched the release rate in pH=7.4buffer solution and environmental stability. The results showed that the drug load were345μg and206μg of CDDP loaded per milligram. Within100h of continuous sampling, the system of HMS-CMCS/CDDP has released90%, while the system of HMS/CDDP has released only70%. The results showed that those HMS-CMCS microspheres had a significant release behavior and good environmental stability. It will be a suitable drug carrier for controlled release.4. We investigate the enzymatic activity of pectinase adsorbed on HMS-CMCS microspheres. The stability was not impeded by the adsorbed proteins despite the fact that up to231.5mg of enzyme was adsorbed per gram of the carrier particles. Respectively, the immobilized pectinase revealed acceptable temperature/pH stability, and the optimum temperature/pH also increased The immobilized enzyme retained40%of its initial activity over40days, while the free enzyme only retained10%. |
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