【作者】 陈峰；

【导师】 万谦宏；

【作者基本信息】 天津大学 ， 应用化学， 2010， 博士

【摘要】 磁性介孔硅胶微球具有表面积大、表面易于官能团化、生物相容性好且在磁场下易于分离、易于实现分离操作自动化等优点而被广泛应用于催化、固定化酶、核酸提取、细胞筛选,药物缓控释等方面,成为材料化学,分离科学,生物技术和药物研发等多个领域的研究热点。目前磁性硅胶介孔微球主要通过浸渍法、包覆法和模板法制备,所得产品具有较高的残余磁性,在外加磁场撤离后,仍表现出颗粒团聚现象,一定程度上阻碍了微球的反复利用。因此,发展高磁响应性和超顺磁性的的硅胶介孔微球的制备方法,并实施微球的表面官能团化,进一步拓宽磁性材料的应用领域,具有十分重要的科学意义和实用价值。在本论文中,作者通过脲醛树脂缩聚反应诱导纳米粒子团聚生成微米微球的途径,首先制备了具有高磁响应性γ- Fe₂O₃@ SiO₂介孔微球,建立了硅胶基质中由Fe₃O₄相变生成γ- Fe₂O₃粒子的实验条件。接着采用脲醛树脂模板法制备了两种超顺磁性硅胶介孔微球并探讨了它们在固定化酶,核酸纯化,生物样品预处理和手性分离等方面的应用。论文主要内容如下:1)采用直接300oC空气中氧化法对以铁溶胶为磁性前体所制备磁性介孔Fe₃O₄@SiO₂微球进行氧化,将室温下长期存放不稳定的Fe₃O₄转化为具有较高磁响应性和化学稳定性的γ- Fe₂O₃,解决了长期放置所带来的磁性降低问题,并将其用于对青霉素酰化酶固定,研究了不同固定化酶方法对固定化酶活力的影响。2)以磁流体和硅溶胶为原料通过脲醛树脂模板聚合法,得到Fe₃O₄ @ SiO₂ @UF微球,然后通过高温氧化法直接将模板去除同时转化Fe₃O₄为γ- Fe₂O₃得到了超顺磁性γ- Fe₂O₃@ SiO₂介孔微球。并且以该微球作为磁性固相萃取材料从豌豆和青椒中提取植物基因组DNA,所得到的DNA模板可以通过PCR扩增,用于植物中转基因成分的检测。3)所制备的γ- Fe₂O₃@ SiO₂超顺磁介孔微球的孔道约为6 nm,分子量较大物质如蛋白质等难以进入,因此是理想的限进材料基质。通过对其表面进行修饰,制备了孔道内表面键合疏水性烷基而外表面为亲水性二醇基的限进材料,做为牛血清白蛋白溶液中α、β-萘酚的固相萃取剂,用于生物样品的前处理工作。4)采用十六烷基三甲基溴化铵（CTAB）和四乙氧基硅烷（TEOS）混合溶液对超顺磁性γ- Fe₂O₃介孔微球进行溶胶-凝胶法处理,得到孔径约60 nm超顺磁性Core-Shell结构的介孔微球。扩孔后的磁性载体增加了固定化脂肪酶的活性,用于医药中间体β-氨基酸对映体的酶拆分制备。更多还原

【Abstract】 Magnetic mesoporous silica microspheres have drawn considerable attention in recent years owing to their advantageous characteristics such as large surface area, versatile surface functional groups, excellent biocompatibility, ease of separation from solution and being amenable to automation. These magnetic particles can be used in various areas including catalysis, immobilized enzymes, DNA purification, cell separation, and controlled drug delivery. There are a variety of approaches available for the preparation of magnetic mesoporous silica microspheres, including the methods of impregnation, encapsulation and template synthesis. One common problem with all these methods is that they mostly give rise to ferromagnetic microspheres with relatively high residual magnetism that causes particle aggregation even if the external magnetic field is removed. The particle aggregation prevents the recycled uses of these microspheres, thus lowering the performance of these materials in many applications. The objectives of this thesis are to develop new methods for preparation of superparamagnetic mesoporous silica microspheres and to further demonstrate their applications through surface modification. Firstly, ferromagneticγ- Fe₂O₃@ SiO₂ microspheres were prepared by oxidation of Fe₃O₄@ SiO₂ microspheres, which were obtained through urea-formaldehyde resin templated synthesis route. The materials were used as magnetic matrices for immobilization of penicillin acylase. This work was followed by fabrication of two types of suerparamagneticγ- Fe₂O₃@ SiO₂ microspheres through modifications to the templated method developed previously and exploration of their applications in DNA purification, solid-phase extraction, and chiral separation. The detailed contents of this thesis are as follows:1) Through oxidation of Fe₃O₄@SiO₂ mesoporous microspheres which were prepared with iron sol as magnetic precursor in 300oC to transform Fe₃O₄ intoγ- Fe₂O₃. Theγ-Fe₂O₃ nanoparticles have similar saturation magnetization but higher chemical stability than Fe₃O₄, implying that the particles could retain their magnetization longer when exposed to air during storage. Futher, we applied the modified microspheres on immobilization of penicillin acylase and studied the effects of immobilization conditions on immobilized enzyme activity. 2) A modification to the above method was introduced to prepare superparamagn etic mesoporous silica microspheres. Fe₃O₄ @SiO₂ @UF microspheres were prepared by polymerization of magnetic fluid and silica sol with urea-formaldehyde as template. The composite particles were then subject to calcinations for removal of the template and transformation of Fe₃O₄ intoγ-Fe₂O₃ to yield superparamagneticγ-Fe₂O₃@SiO₂ mesoporous microspheres. The prepared microspheres were used for solid phase extraction of genomic DNA from pepper and pea. The DNA templates isolated were amplifiable by polymerase chain reaction （PCR） and therefore potentially applicable for detection of genomic modification organism in plants.3) The superparamagneticγ-Fe₂O₃@SiO₂ mesoporous microspheres are ideal to serve as matrix for restricted access materials （RAM） because of their average pore diameters around 6nm allowing discrimination of small molecules from large molecules such as proteins. The internal surface of the above magnetic microspheres was bonded with hydrophobic alky chains whereas the external surface was made hydrophilic by encapsulation with diol groups. The alkyl/diol functionalized magnetic RAM was used for extraction ofα,β-naphthols in the presence of bovine serum albumin （BSA）. This type of materials could be used in the pretreatment of biologic samples for clinical applications.4) Magnetic mesoporous microspheres with large pore sizes are desirable for enzyme immobilization. A further modification to the templated synthesis method was introduced to prepare the superparamagnetic core-shell mesoporous microspheres with pore diameters in the range around 60 nm. Theγ-Fe₂O₃ mesoporous microspheres were served as the magnetic cores whereas the porous silica shells were formed by sol-gel process involving hydrolysis and condensation of tetraethoxyl silane （TEOS） in the presence of cetyl quaternary amine bromide （CTAB）. The removal of the CTAB molecules from the composite particles leaves the material with regular pores of diameter about 60 nm. The prepared core-shell magnetic mesoporous microspheres were superparamagnetic and could be repeatedly used for chiral separation ofβ-amino acids after immobilization with lipase.更多还原