【作者】 甘勇；

【导师】 郭广生；

【作者基本信息】 北京化工大学 ， 应用化学， 2010， 博士

【摘要】 将生物矿化过程引入到材料合成中,制备结构和性能新颖的无机材料并解释其在有机基质调制下的形成机理,具有重要的意义和广阔的应用前景。本论文采用仿生合成法,以明胶为有机基质,利用其分子结构特性以及在外界环境影响下的自组装性能,调控羟基磷灰石、碳酸钙以及氧化锌等无机生物活性材料的合成并研究其生成机理,具体内容如下：羟基磷灰石(HA)具有良好的生物活性和相容性,是理想的硬组织替代材料。论文首先采用明胶为有机基质仿生合成了羟基磷灰石纳米材料。研究了明胶作为有机基质矿化合成羟基磷灰石的机理及粒子的组装过程,讨论了矿化合成的羟基磷灰石材料的生物活性和离子交换性能。分析结果表明：明胶分子侧链羧基与钙离子之间的静电作用诱导羟基磷灰石晶体的成核和生长并对羟基磷灰石晶体的自组装起重要作用。钙离子与明胶浓度比对羟基磷灰石的形貌有较大影响,随着浓度比的增大,产物形貌由球形纳米粒子转变成纳米棒和纳米片单元结构。对制备的羟基磷灰石产物进行了Cd2+的离子交换实验,发现其对Cd2+离子置换率可达80.2%。锶的掺杂有利于提高羟基磷灰石的结晶性、溶解性和生物降解性。本论文采用明胶为基质矿化合成锶钙磷灰石空心纳米球,讨论了锶钙离子浓度比对产物形貌的影响。研究发现：当锶钙离子浓度比为1：1时,得到粒径为50-100nm的空心锶钙磷灰石纳米球,其形成过程是晶体在明胶分子诱导下的异相成核以及进一步组装成的实心球,再通过Ostwald晶化形成的。以亚甲基蓝为装载药物,对空心锶钙磷灰石纳米球进行了模拟药物释放实验,发现其最大装载量为105mg/g。在释放过程中,2h内累计释放量为18.9%,48h后释放量达到90%,表明空心锶钙磷灰石纳米球具有明显的缓释效果。对锶磷灰石矿化合成的研究表明,明胶浓度较低(1wt%)时,合成了带状产物；当明胶浓度较高(3wt%)时,合成了片状产物以及由纳米片组装形成的纳米“绣球”。作为贝壳的主要组成部分,碳酸钙是另一种重要的生物活性材料。本文以明胶为基质矿化合成碳酸钙,考察了明胶浓度、钙离子浓度、晶化时间和矿化温度对碳酸钙组成及结构的影响。研究结果表明：明胶和钙离子的物质的量比对产物结构有较大影响,随着物质的量比的逐渐减小,产物由致密球体结构转变为双螺形、类球形以及疏松球体结构；另外,明胶分子还可稳定球霰石晶相的存在,但最终由于球霰石向方解石晶相的转化导致了凹孔结构碳酸钙的出现。另外,论文还对比研究了其他基质,如PEG、PVP、CTAB、SDS表面活性剂对碳酸钙产物形貌的影响,研究发现离子型表面活性剂对产物形貌具有较大影响,这可能是由于离子型表面活性剂引起了明胶分子的构象改变造成的。同时,本论文还以明胶为基质合成了碳酸镁、碳酸锶、碳酸钡等系列碳酸盐材料,考察了离子半径大小对产物形貌的影响。研究结果表明：离子半径越大,形成产物的粒径越小,产物结构越发散,这可能是离子半径大小对明胶分子的构象产生影响,随着离子半径的增加,明胶分子的构象从聚集团状转变为发散状态,进而影响产物的形貌：从致密聚集的“巢”状结构和球形体到分散的哑铃结构和枝状结构。同时,研究了其他纳米碳酸盐材料,如棒状碳酸镍和碳酸钴、哑铃状碳酸锰和球状碳酸镉,表明产物形貌还可能受到金属元素原子量的影响。系列磷酸盐及碳酸盐的矿化结果为其他无机功能材料的仿生合成提供了指导意义。最后,本论文采用仿生矿化法合成了氧化锌功能纳米材料。研究结果表明：明胶浓度、锌离子浓度、矿化时间、矿化温度和沉淀剂种类对矿化过程及产物都具有较大影响。随着矿化时间的延长,氧化锌实现了由片状-花状-花生状-哑铃状的结构转变,发现了不同结构氧化锌由于纳米效应而产生的紫外蓝移现象。气敏性能测试结果表明：花生状氧化锌对乙醇有较好的气敏性能,当乙醇浓度为40 ppm时,响应灵敏度可达25。更多还原

【Abstract】 The general principles of biomineralization are introduced into the synthesis process of inorganic materials. Simulating the biomineralization process of inorganic materials with novel performance and structure and interpreting the organic matrix modulation mechanism, have important implications and a wide range of prospects. In this paper, a biomimetic synthesis method using gelatin as matrix was used to obtain hydroxyapatite, calcium carbonate and zinc oxide. Taking advantage of its molecular structure characteristics and self-assembly performance in outer environment was modulated to inorganic bioactive materials and its formation mechanisms. The specific work includes the following:Hydroxyapatite (HA) has good bioactivity and biocompatibility; it is one of the ideal implant materials in hard tissues. Based on the basic principles of biomineralization, hydroxyapatite was synthesized under the control of gelatin used as the organic matrix. The mineralization mechanism and self-assembly process of HA nanoparticles were discussed and the bioactivity and ion exchange of the product were investigated. The results indicate that adsorption of static electricity of side-chain group of gelatin macromolecules reacts with Ca2+ ions in solution, which is capable of controlling the nucleation and growth of HA crystals and plays a key role of the process of self-assembly of hydroxyapatite particles. The concentration ratio of Ca2+ and gelatin has a great impact on HA morphology. As the concentration ratio increasing, the morphologies of products comprise some units of nanoparticles, nanorods and nano-flakes. In the ion-exchange experiments Cd2+ ions are replace by Ca2+ ions among the hydroxyapatite crystals, the rate reach to 80.2%.Strontium-substituted Hydroxyapatite can improve the crystalline, solubility and biodegradable property of hydroxyapatite material. Calcium strontium phosphate hydroxide hollow nanospheres were synthesized using gelatin as organic substrate. Impacting on the morphology of the products the concentration ratio of Ca2+ ions and Sr2+ ions was discussed. The results show that the hollow nanosphere products with 50-100 nm in diameter can be obtained when the concentration ratio is 1:1. Its formation process is the heterogeneous nucleation of crystals on the gelatin molecular side chain and the solid spheres are formed. Further mineralization process, the crystals of the solid spheres constantly produce dissolution and deposition in the solution, and the hollow nanospheres are formed by Ostwald crystallization. Methylene Blue (MB) as a model drug is loaded in the hollow nanospheres, and the maximum is 105 mg/g. In the release process, the cumulative released amount in 2 h is 18.9%, it reaches 90% after the release of 48h. The hollow spherical structure material is suitable for drug release as a drug carrier. The strontium-calcium apatite was biomineralized in the present of gelatin solution and the morphology and structure of the product affected by the concentration of gelatin and Sr2+ ions were discussed. The nanobelts, nanotablets and nanostructure balls were synthesized in the different concentration of gelatin.As a major component of shells, calcium carbonate is another important biological material. Calcium carbonate was synthesized by mineralization using gelatin for a matrix. The influences of factors, namely the concentration of gelatin and Ca2+ ions, the aging time, the reaction temperature, on the composition and structure, were investigated. The results show that the structures of product are controlled by the ratio of the concentration of gelatin and calcium ions. As the ratio of concentration of gelatin and calcium ions gradually decreases, the compact spherical CaCO3 can change to the double-snail-like, analogous spherical-like and loose spherical CaCO3 aggregation. In addition, vaterite is stable in the solution due to the effect of gelatin in the first phase, and the concave hole CaCO3 appears for the phase transformation from vaterite to calcite in the end. In addition, a comparative study of other substrates, such as PEG, PVP, CTAB, and SDS on the effects of calcium carbonate products morphology was in progress. Studies show that ionic surfactant has a large impact on morphology of product. It may be the changes of gelatin molecular conformation caused by the ionic surfactant.At the same time, magnesium carbonate, strontium carbonate, barium carbonate and other series of carbonates were formed by biomineralization, and impacting on the morphology of the product the sizes of positive ionic radius was discussed. The results indicate that the larger the positive ionic radius, the sizes of the product get smaller and the structures of the product get more divergent. It may be the changes of the gelatin molecule conformation accused by the sizes of positive ionic radius. As the size of ionic radius increases, gelatin molecule conformation shapes from poly group and converts to a decentralized state, which affects the morphology of the products, such as from the compact "nest"-like structure and sphere to the dumbbell-shaped structure and dendritic structure. Furthermore, nanorods carbonated nickel and cobalt carbonate, dumbbell-shaped manganese carbonate and spherical cadmium carbonate were obtained. It indicates that the gelatin conformation of molecules is also limited by the effects of atomic weight.The results of series of phosphate and carbonate mineralized in gelatin solution provide guidance for biomimetic synthesis other inorganic materials. Zinc oxide was synthesized by the biomimetic process in the gelatin solution at low temperature, and the nucleation, growth and self-assembly of ZnO crystals in the course of mineralization synthesis was studied. The results indicate that the gelatin concentration, the zinc ion concentration, the mineralization time, the temperature and precipitation agent of mineralization on mineralization process and products have a larger impact on the product. With the extension of time for mineralization, the sheet-like, flower-like, peanut-like zinc oxide is changed to dumbbell-like zinc oxide. A different structure ZnO producing the effect of UV blue shift due to the effect of nanometer was found. Gas performance test results indicate that the peanut-like zinc oxide have a better of sensing properties on alcohol. The sensitivity reaches 25 when the concentration of ethanol is 40ppm.更多还原