【作者】 郑浩然；

【导师】 吴惠霞；

【作者基本信息】 上海师范大学 ， 无机化学， 2010， 硕士

【摘要】 磁性纳米粒子具有独特的磁学性质,如超顺磁性和高饱和磁化强度等,而且生物相容性较好,毒副作用小,在靶向药物载体、磁共振成像、细胞和生物分子分离、免疫检测等生物医学领域具有广阔的应用前景,因此近年来备受人们青睐。为了拓宽磁性纳米粒子在各个领域的应用,人们对磁性纳米粒子进行各种表面修饰从而实现其功能化。据文献报道,对磁性纳米粒子进行光学修饰制备的磁光双功能纳米材料具有优良的磁性和发光性能,在磁学、荧光、生物和医药等领域得到广泛应用,特别是在超高密度信息存储、生物分子识别、药物传输等方面具有诱人的应用前景。本文主要研究Fe3O4、CoFe2O4磁性纳米粒子的制备,二氧化硅包裹和发光材料修饰以及在MRI方面的应用。全文共三章。第一章概述了磁性纳米材料的制备、修饰及应用前景,核壳结构磁性纳米粒子／二氧化硅复合纳米材料以及磁光双功能纳米材料的制备和应用并提出了论文的研究设想。第二章采用化学共沉淀法,以FeCl3·6H20和FeCl2.4H2O为原料,氨水为沉淀剂,首先在不同种类醇—水体系中制备磁性Fe3O4纳米粒子,并用TEM,XRD对产物进行表征。结果表明,所制得的纳米粒子形貌随醇—水体系极性和黏度的变化由圆球形向棒状结构过渡,而且粒径增大,分散性提高。这些纳米粒子能够稳定分散在水中。以油酸为表面活性剂对乙醇—水体系制备的Fe3O4纳米粒子进行表面修饰,发现经过修饰后的纳米粒子分散性改善,并且能够从水相转移到有机相中。其次以柠檬酸为表面活性剂,制备了能稳定分散在水中的磁性Fe3O4纳米粒子。此Fe3O4纳米粒子饱和磁化强度Ms达50.2 emu/g,具有良好的超顺磁性。磁共振成像实验研究表明,制备的四氧化三铁纳米粒子具有较大的横向驰豫系数r2(119.74 Fe mM-1s-1)和纵向驰豫系数r1(13.64 Fe mM-1s-1),因此该Fe3O4纳米粒子既可以作为T2对比剂,又可以作为T1对比剂；接着,我们以此Fe3O4纳米粒子为种子,在Triton X-100／正己醇／环己烷／水反相微乳体系中,采用碱催化正硅酸乙酯的水解、缩合,制备了具有核壳结构的Fe3O4@SiO2复合纳米粒子。研究了搅拌方式、TEOS的浓度对Fe3O4@SiO2纳米粒子形貌的影响。结果表明采用机械搅拌能够有效地控制复合纳米粒子的形貌,形成分散性好且形貌为圆球形的核壳纳米粒子。随着TEOS浓度的增加,SiO2壳层增厚,复合粒子形貌更均匀。最后,Fe3O4@SiO2纳米粒子通过修饰3-氨丙基三乙氧基硅烷(APTES)使其表面氨基功能化,然后利用硅烷偶联剂的氨基与有机小分子丹磺酰氯反应形成丹磺酰亚胺发光基团,从而合成了磁光双功能的Fe3O4@SiO2@APTES-Dy纳米复合材料。采用TEM, FT-IR, UV-vis, XRD, XPS等技术对所得产物进行了表征,并研究了材料的磁学性质和发光性能。为了考查材料在生物、医学领域应用的可行性,我们对纳米复合材料Fe3O4@SiO2@APTES-Dy进行了细胞毒性测试和磁共振成像(MRI)研究。结果表明,Fe3O4@SiO2@APTES-Dy具有较好的磁共振成像效果且细胞毒性较小,是一种优良的磁共振成像T2对比剂。细胞切片TEM显示,复合纳米粒子能够穿过Hela细胞的细胞膜进入内涵体和细胞质中。第三章我们尝试用共沉淀法、水热法、热解法三种方法制备了铁酸钴纳米粒子。其中化学共沉淀法制备的铁酸钴纳米粒子虽然是水溶性的但粒径较大,不利于二氧化硅包覆,也限制了其在生物方面的应用。水热法制备的铁酸钴纳米粒子主要分两种类型,其中一部分是较小的纳米粒子成圆球形,分散性较好；另一部分大的花状纳米粒子是由数个小的铁酸钴纳米粒子组合而成。CoFe2O4纳米粒子的饱和磁化强度Ms达53.2 emu/g,具有良好的超顺磁性。磁共振成像实验研究表明,溶剂热法制备的CoFe2O4纳米粒子的横向驰豫系数r2为36.54 FemM-1s-1,可以作为T2成像对比剂。热解法制备的铁酸钴纳米粒子粒径较小,平均粒径为5nm左右,很容易对其进行二氧化硅包覆得到单分散的核壳结构的CoFe2O4@SiO2,使其从油溶性转变为水溶性。包覆二氧化硅后的铁酸钻纳米粒子通过修饰硅烷偶联剂使其氨基功能化,然后利用表面的氨基与发光染料丹磺酰氯反应,形成磁光双功能纳米粒子CoFe2O4@SiO2@APTES-Dy.采用各种电镜技术和光谱技术对所得纳米复合材料进行了表征,并研究其细胞毒性和MRI成像。结果表明,复合纳米材料CoFe2O4@SiO2@APTES-Dy具有较好的磁共振成像效果且细胞毒性较小,是一种优良的磁共振成像T2对比剂。更多还原

【Abstract】 Magnetic nanoparticles have shown broad application prospects in biomedical field, including targeted drug delivery system, magnetic resonance imaging (MRI), cellular and bio-molecular separation, and immune detection, because of their unique magnetic properties (such as superparamagnetic and high saturation magnetization), good biocompatibility and low toxicity. Therefore, they have attracted great interests in recent years. To broaden the application of magnetic nanoparticles in various fields, a series of surface modifications were carried out to fabricate functional materials. According to the literature, the magnetic nanoparticles modified by optical materials can produce the magnetic-optical bifunctional nanomaterials with excellent magnetic and luminescent properties, which are widely used in magnetic, fluorescent, biological and pharmaceutical fields, especially with attractive prospect for application in the ultra-high density data storage, bio-molecular recognition, drug delivery, etc. This thesis mainly studies the preparation of Fe3O4 and CoFe2O4 magnetic nanoparticles, silica coating and modification with luminescent materials, as well as the applications of the nanocomposites in MRI. The contents of this thesis include three chapters.Chapter 1 summarizes the synthesis, modification and application of magnetic nanoparticles, the preparation and application of core-shell structural magnetic/silica nanoparticles and magnetic-optical bifunctional nanomaterials. The research envisagement for the whole thesis was also proposed.In chapter 2, First, Fe3O4 nanoparticles were synthesized in different alcohol-water solvent systems by a facile chemical coprecipitation process using ammonia as precipitant, FeCh·6H2O and FeCl2·4H2O as Fe sources. The nanoparticles were then characterized by TEM (transmission electron microscopy) and XRD (X-ray diffraction) techniques. Along with the decrease of polarity and the increase of viscosity of the solvent systems, the morphology of Fe3O4 nanoparticles changed from spherical to rod-like structure, the particle size increased, and the dispersion of the nanoparticles was improved. The produced nanoparticles can be well re-suspended in water. The surface modification of Fe3O4 nanoparticles synthesized in ethanol-water system was carried out using oleic acid as surfactant. After surface modification with oleic acid, the nanoparticles can be transferred from aqueous phase to organic phase.Second, chemical co-precipitation method was employed to synthesize Fe3O4 nanoparticles which can be well dispersed in water by using citric acid as a surfactant. The as-synthesized Fe3O4 nanoparticles showed a good superparamagnetic property with high saturation magnetization (Ms=50.2 emu/g). The r1 and r2 relaxivities of as-synthesized magnetite nanoparticles are found to be r1 (13.64 Fe mM-1 s-1) and r2 (119.74 Fe mM-1 s-1), respectively. Such values for r1 and r2 suggest that the as-synthesized magnetite nanoparticles can act as both T1 and T2 contrast agents. Afterwards, by using Fe3O4 nanoparticles with citric acid as a surfactant as seeds in a Triton X-100/hexanol/cyclohexane/water reverse microemulsion system, the core-shell structural Fe3O4@SiO2 nanocomposite particles were prepared via hydrolysis and condensation of tetraethyl orthosilicate (TEOS) under the catalysis of alkali. The effects of different stirring methods and the concentration of TEOS on the morphology of Fe3O4@SiO2 nanoparticles were investigated. The results showed that the mechanical stirring could effectively control the morphology of the composite nanoparticles to form a good dispersion and spherical morphology of core-shell nanoparticles. With the increase of TEOS concentration, the thickness of the SiO2 shell layer increases, and the morphology of the obtained composite particles become more uniform.Finally, the Fe3O4@SiO2 nanoparticles were subsequently modified with 3-aminopropyl-triethoxysilane (APTES) to to immobilize amino groups onto the particle surfaces, then dansyl groups were chemically attached onto the nanoparticles by nucleophilic substitution of sulfonyl chloride with primary amines, resulting the formation of magnetic-optical bifunctional Fe3O4@SiO2@APTES-Dy nanocomposites. Extensive characterizations of the obtained nanocomposites have been performed using TEM, FT-IR spectra, UV-vis spectra, XRD and X-ray photoelectron spectroscopy (XPS). Their magnetic and fluorescent properties were also studied. To investigate their possible applications in biology and medicine fields, the cell toxicity and MRI of the Fe3O4@SiO2@APTES-Dy composites were determined. The results showed that the nanocomposites could be used as excellent T2 contrast agents of MRI due to their good effect of MRI and very low toxicity. TEM observations of the cells incubated with the nanoparticles showed that the Fe3O4@SiO2@APTES-Dy nanocomposites could be endocytosed by the cells and then distributed in the endosome and cytoplasm.In chapter 3, we tried to use co-precipitation, solvothermal method, and thermal decomposition to prepare cobalt ferrite (CoFe2O4) nanoparticles. Although water-soluble CoFe2O4 nanoparticles could be prepared by chemical co-precipitation, their larger particle size was not convenient for silica coating, which limited their biological applications. CoFe2O4 nanoparticles prepared by the solvothermal process were composed of two kinds of particles. Some are well-dispersed small size nanoparticles, and others are large flower-like particles consisting of several small nanoparticles. The as-synthesized CoFe2O4 nanoparticles prepared by solvothermal process have a good super-aramagnetic property and their saturation magnetization Ms=53.2 emu/g. Their r2 relaxivity was found to be 36.54 Fe Mm-1 s-1 from MRI. Such a value for r2 suggests that the as-synthesized magnetite nanoparticles can act as T2 contrast agents.CoFe2O4 nano-particles prepared by thermal decomposition showed an average diameter of about 5 nm, and it is easier to coat them with silica layer resulting the core/shell structural CoFe2O4@SiO2. After silica coating, the oil-soluble CoFe2O4 nanoparticles easily dissolved in water. The CoFe2O4@SiO2 nanoparticles were subsequently modified with APTES to introduce amino groups on their surfaces, and then the magnetic-optical bifunctional CoFe2O4@SiO2@APTES-Dy nanoparticles were obtained by the nucleophilic substitution reaction between the surface amino groups and dansyl chloride.Extensive characterizations of the produced nanocomposites have been performed by using a variety of microscopy and spectroscopic techniques. The cell toxicity and MRI studies of the as-prepared CoFe2O4@SiO2@APTES-Dy nanocomposites showed that the composite nanoparticles with very low cell toxicity might function as an excellent T2 contrast agent of MRI.更多还原