【作者】 陶可；

【导师】 孙康；

【作者基本信息】 上海交通大学 ， 材料学， 2008， 博士

【摘要】 磁性纳米颗粒由于表现出超顺磁性和良好的生物相容性,因而在生物医用领域有着广阔的应用前景,例如可用作细胞标记物、磁共振造影剂、靶向药物载体或热疗介质等。随着这些领域的发展,对磁性纳米颗粒的制备、修饰等方面的要求也越来越高。因此本文选择了磁性纳米颗粒中应用最为广泛的Fe3O4纳米颗粒,从制备与修饰两个方面进行了研究,并初步证实了经修饰的Fe3O4纳米颗粒对细胞转染的可行性。对这一方向的研究不仅为应用打下了基础,也具有重要的科学意义。首先,本文提出了并验证了制备水溶性Fe3O4纳米颗粒的一种新型界面共沉淀方法。在这一方法中,将二价与三价铁盐按比例溶解于水中,同时将二正丙胺溶于环己烷中作为铁离子的沉淀剂。由于二正丙胺很难溶于水,因此共沉淀反应被限制在水/环己烷界面上进行,能够制备大小为5-15nm的Fe3O4纳米颗粒,这种纳米颗粒被证实表面吸附有铵盐,因而具有良好的亲水性,能够在纯水中长时间保持稳定。此方法简单、易操作,使之有可能进行规模化生产。研究结果表明:界面共沉淀法与经典共沉淀法一样,都有一反应物浓度的临界值,当反应物浓度低于此值时,将不会生成Fe3O4纳米颗粒。但是,界面共沉淀法表现出一些特性,例如,能够获得Fe3O4的浓度范围变小;反应温度和浓度并不对产物的粒径产生明显影响,但通过温度的改变可调节产物在水中的稳定性及磁性能。实验结果揭示了界面共沉淀法与经典共沉淀法的异同点,证实了该反应在水/油界面上进行,据此我们提出了界面共沉淀法的机理。在上述工作基础上,本文将界面共沉淀法进一步拓展用于制备葡聚糖修饰的Fe3O4纳米颗粒,并研究了葡聚糖用量、分子量对产物性能的影响。相较于经典共沉淀法,在加入相同量的葡聚糖及相同的反应条件下时,界面共沉淀法能够获得粒径较大、葡聚糖的含量较少、饱和磁化强度更高的纳米颗粒。通过对形核理论的探讨我们认为,在葡聚糖存在的环境下制备四氧化三铁时,其颗粒优先在葡聚糖分子链上以及分子链的缠结处形核,并相互缠结而团簇结构;另一部分葡聚糖将包裹在团聚体外使之稳定。基于这一结构模型,界面共沉淀法产物性能的提高被认为是反应在界面上进行所导致的。然而,采用共沉淀法制备的葡聚糖/Fe3O4纳米颗粒在水中分散稳定性、结晶度等方面仍然不能满足生物医用的需要,因此本文采用了二甘醇作为反应溶剂,由于其具有较高沸点(245℃)而使反应可在相对较高的温度下进行。从而能够使产物结晶性得以提高,同时,产物在水中具有更高的分散稳定性,并被证实来源于二甘醇在纳米颗粒与大分子杂化后在表面的进一步吸附。另外,这种方法能够在制备不同种类的水溶性大分子修饰Fe3O4纳米颗粒中具有良好的普适性。本文采用了微乳液法对Fe3O4纳米颗粒进行了SiO2包裹的初步研究,证实包裹层的厚度能随着Fe3O4纳米颗粒的加入量及SiO2的加入量的改变而改变,产物具有较高的饱和磁化强度。但目前对包裹后产物的粒径及形貌的控制还不理想,有待进一步的研究。本文还对葡聚糖/Fe3O4纳米颗粒进行了骨髓基质干细胞的转染的初步研究,普鲁士蓝染色观察证实了这种纳米颗粒可以成功转染至骨髓基质干细胞中,并发现当Fe3O4浓度小于32μg/ml时,对细胞的繁殖几乎不产生不良作用;而浓度在32μg/ml以上时,则将抑制细胞的生长和繁殖。这一探索为进一步的分子影像学及细胞示踪研究打下了良好的基础。更多还原

【Abstract】 Magnetic nanoparticles, which display superparamagnetic property and biocompatibil-ity, have been found wide potential applications in biomedical fields. For example, theycan be used as magnetic resonance image (MRI) agents, drug delivery carrier, and used inhyperthermia, DNA and protein bioseparation, etc. Along with the development in thesebiomedical fields, the requirements for the synthesis and modification of magnetic nanopar-ticles are improving. Therefore, the Fe3O4 nanoparticles (MNPs), which were researchedmost intensively, were chosen in this thesis.A novel interfacial coprecipitation method was proposed to prepare MNPs. In thisapproach, ferrous and ferric precursors were solved in water, while di-n-propylamine wasdiluted by cyclohexane to be used as precipitation agent. Therefore, the coprecipitationreaction was confined to the interface between water and oil because dipropylamine can notbe solved in water. MNPs were nucleated on the interface and move toward water phase,after they immersed in water completely, they would stop growing because of the absence ofalkali. As a result, about 10±5nm-sized MNPs can be prepared, and they possess relativelygood hydrophicility and stability in water. It is confirmed that the resultant MNPs possessnot only relatively narrow size distribution but also a hydrophilic amine-decorated surface,which provides them with the capability of being further modified.Consequently, we studied the interfacial coprecipitation mechanism by evaluating theeffects of the concentration of precursors and the temperature in preparation. If the concen-tration of Fe2+ is lower than about 7.5 mmol/L, no matter what concentration of the amine is,Fe3O4 would not be synthesized. The interfacial coprecipitation follows the mechanism ofseparated two steps, which is similar to the coprecipitation happens in homogeneous aque-ous medium. When the concentration of iron salt is higher than the critical limit, the sizeof the resultant nanoparticles would not change significantly. The effect of preparation tem-perature is totally different from the coprecipitation in aqueous medium, especially on thesize. In the interfacial coprecipitation, the size would not increase and dispersibility would be modified with the temperature increasing, which is caused by the mechanism of the for-mation of MNPs and their surface chemistry. Our efforts further confirmed the mechanismof formation of the nanoparticles in interfacial coprecipitation method, and the reaction pro-cedures of the coprecipitation, which maybe helpful for the phase control in the preparationof MNPs.Dextran, which is a kind of biocompatible macromolecule was chosen to modify MNPs.Both classical and interfacial coprecipitation were utilized to prepared dextran/MNPs hybridnanoparticles. The in?uences of the mass and molecular weight of dextran on the interfacialcoprecipitation were evaluated, and the comparison of two methods were carried out. Basedon the classical theory of nucleation, it is believed that the macromolecular chains can playthe role as a substrate for the nucleation of magnetite, thus to make the nanoparticles grow ona dextran chain just like pearls on a necklace. Furthermore, these”necklaces”can aggregateas clusters. The classical nucleation theory also shows that the shape and size of nanoparticlecould be affected by the shape of macromolecular chains and the interface tension betweenmacromolecule and MNPs. It was found that the content of dextran of resultant sampleprepared by interfacial coprecipitation is less than that prepared by the classical coprecipi-tation. Meanwhile, the saturation magnetization of nanoparticles prepared by the interfacialcoprecipitation is much higher than those prepared by the classical coprecipitation, which ismainly caused by their difference in dextran percentage.However, some drawbacks were found in the coprecipitation strategy, such as the dis-persibility, crystallinity, etc. Therefore a novel method were put forward for overcomingthese drawbacks, in which diethylene glycol was used as solvent to partly reduce ferrousion. Because of the relative high reaction temperature (about 220℃), the crystallinity of as-prepared nanoparticles was improved. Meanwhile, the dispersibility was also improved orig-inated from diethylene glycol absorbing on nanoparticles surface. In addition, this method isgeneral for many kinds of water-soluble macromolecules to modify the magnetite nanopar-ticles.Microemulsion method was utilized to coat a large mount of MNPs by silica layer.The thickness of coating layer can be easily tuned by the amount of Fe3O4 and silica, andthe resultant particles possess a relative high supersaturation magnetization. However, thecontrol of the size and shape of nanoparticles is difficult, which needs further studies.The transfection of magnetite nanoparticles to cell was evaluated and the results showsthat dextran/magnetite hybrid nanoparticles can be successfully transfected to bone marrowstem cells. When the concentration of magnetite is below 3232μg/ml, they almost have no in?uence on the differentiation of cells. This experiment identify the possibility of furtherresearch on the molecule and cell image and tracking.更多还原