【作者】 郭亚平；

【导师】 周玉；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2009， 博士

【摘要】 磷灰石是人体中骨、牙齿等硬组织的主要无机成分,具有优良的生物相容性、生物活性、骨传导性、无毒性和非炎性等优点,因此人工合成的磷灰石粉末或者涂层被广泛的应用于骨填充材料和替代材料。最近,研究表明材料的生物活性不仅与材料的化学组成有关,还与材料的孔径、孔容、孔结构等显微结构有关。生物材料的介孔结构能促进细胞黏附、生物代谢物的吸收,控制材料的再吸收速度使其与骨组织修复速度相匹配。本文提出了化学浸泡法、类乳液法、电泳沉积-化学浸泡法,并制备了介孔磷灰石微球和涂层。采用XRD、FTIR、SEM、TEM、XPS、BET、TG-DSC等分析手段表征了介孔磷灰石微球和涂层的形貌、物相、介孔结构和体外磷灰石形成活性,探讨了介孔磷灰石微球和涂层的形成机理。热力学计算表明贝壳粉末和碳酸钙粉末经磷酸缓冲溶液（PBS溶液）处理后在低温下能够转化成磷酸钙盐。磷灰石在热力学上比其它磷酸钙盐更稳定,但是转化产物受PBS溶液的pH值控制。如果溶液pH值保持在6.0或者6.4,则转化产物为磷酸八钙（OCP）和磷酸氢钙（DCPD）,如果溶液pH值保持在7.4或者8.0,则转化产物为磷灰石。磷灰石的形成机理是溶解-沉淀反应,即贝壳粉末和碳酸钙粉末浸泡到PBS溶液后,小颗粒率先溶解,游离出的钙离子与溶液中磷酸根离子反应生成磷灰石并沉积在大颗粒表面。提高磷灰石转化率的方法包括减少粒径、延长反应时间和增大PBS溶液浓度等。碳酸钠溶液与含贝壳有机质的氯化钙溶液通过沉淀反应制备了碳酸钙微球。采用化学浸泡法和类乳液法将碳酸钙微球转化成低结晶度的缺钙型介孔磷灰石微球。磷灰石晶格中的部分PO₄^3-离子被CO₃^2-离子和HPO₄^2-离子取代。采用化学浸泡制备的介孔磷灰石微球的形貌不规则,粒径分布不均匀,其吸附-脱附等温线为IV型,含有H₃型迟滞环,对应的BJH孔径分布曲线为单峰结构,峰位置位于3.9 nm。在Na₂HPO₄/十六烷基三甲基溴化铵（CTAB）/环己烷/正丁醇乳液体系中,采用类乳液法制备了单分散的介孔磷灰石微球,粒径约5μm,其吸附-脱附等温线也为IV型,含有H₃型迟滞环,对应的BJH孔径分布曲线为双峰结构,峰位置位于3.9 nm和9.0 nm。延长反应时间和提高反应温度会导致孔径为9.0 nm的介孔消失。磷灰石微球的介孔结构形成原因取决于磷灰石纳米粒子的堆积,通过直接或者以CTAB胶束为模板堆积形成孔径分别为3.9 nm和9.0 nm的介孔。采用电泳沉积-化学浸泡两步法制备了介孔磷灰石涂层,即首先将贝壳粉末或者碳酸钙粉末电泳沉积到Ti6Al4V基体表面形成贝壳涂层或碳酸钙涂层,然后经PBS溶液处理转化成介孔磷灰石涂层。贝壳涂层或者碳酸钙涂层在PBS溶液中浸泡1天后转化成具有片状形貌的介孔磷灰石涂层,孔径分布在3.9 nm。当浸泡时间延长到9天,涂层形貌由片状转化成海绵状,而且介孔结构部分消失。Ti6Al4V基体经H₃PO4/HF溶液处理后,表面形成一层无定形的TiO_x,同时吸附少量的PO₄^3-离子。在贝壳涂层转化成磷灰石涂层过程中,TiO_x和PO₄^3-离子能够促进磷灰石的形成,导致TiO_x氧化层中存在Ca、P、Ti的梯度分布。模拟体液（SBF）浸泡实验表明:介孔磷灰石涂层由于低Ca/P比、介孔结构和贝壳有机质,因此浸泡到SBF溶液后涂层表面能够快速沉积上一层磷灰石。采用电泳沉积-化学浸泡两步法制备了磁性介孔磷灰石涂层,即首先将CaCO₃/Fe₃O₄粉末电泳沉积到Ti6Al4V基体表面形成CaCO₃/Fe₃O₄涂层,然后经PBS溶液处理转化成磁性介孔磷灰石涂层。将CaCO₃/Fe₃O₄涂层浸泡到PBS溶液后,片状磷灰石沉积在CaCO₃/Fe₃O₄颗粒表面。Fe₃O₄纳米粒子能够加速碳酸钙转化成磷灰石,磁性碳酸钙涂层在PBS溶液中浸泡1天后残留的碳酸钙只有9.1%,低于无磁性碳酸钙涂层的41.0%。磁性介孔磷灰石涂层的孔径为3.9 nm,即使浸泡时间延长到9天介孔不消失。SBF浸泡实验表明Fe₃O₄纳米粒子能够提高磷灰石涂层的体外磷灰石形成活性。更多还原

【Abstract】 Apatite is a major inorganic component of the hard tissues of human being, and the corresponding synthetic apatite particles and coatings have been used respectively as bone cavity filling materials and artificial bone graft substitutes because of their biocompatibility, bioactivity, osteoconductivity, nontoxicity, and noninflammatory. Recently, the studies have shown that the bone-forming bioactivity of biomaterials is associated not only with their chemical composition, but also with their microstructures, such as pore size, pore volume and pore structure. Mesoporous structure of biomaterials can promote cell adhesion, adsorption of biologic metabolites, and resorbability at controlled rates to match that of tissue repair. In this work, we proposed chemical immersion method, emulsion-like method, and electrophoretic depositon-chemical immersion method, which were used to prepare mesoporous apatite microspheres and coatings. The morphologies, phases, mesoporous structure and formation mechanism of meosporous apatite microspheres and coatings were studied by means of XRD, FTIR, SEM, TEM, XPS, BET, and TG-DSCThermodynamic calculation has shown that nacre powders and calcium carbonate powders can be converted to calcium phosphate phases at low temperatures after soaking in phosphate buffer solutions （PBS）. Although apatite crystals are stabler thermodynamically than other calcium phosphate phases, the conversion products are determined by the pH values of PBS. If the pH value of PBS is kept at 6.0 or 6.4, nacre powders or calcium carbonate powders are converted mainly to octacalcium phosphate （OCP） or dicalcium phosphate dehydrate （DCPD）. If the pH value of PBS is kept at 7.4 or 8.0, the main products are apatite. The formation mechanism of apatite is dissolution-precipitaion reaction. After soaking nacre powders and calcium carbonate powders in PBS, calcium ions are dissolved firstly from the smaller particles, react with PO43? ions to form apatite crystals, and precipitate them on the large particle surfaces. Decreasing particle size, prolonging reaction time, and increasing the concentrations of PBS can improve the conversion percentages of apatite.Calcium carbonate microspheres were prepared by mixing Na2CO3 solution and CaCl₂ solution with nacre organic materials. Both chemical immersion method and emulsion-like method were used to convert cacium carbonate microspheres to mesoporous apatite microspheres with low crystalinity. The PO₄^3- ions in apatite lattice are substituted partially by CO₃^2- and HPO42- ions. The mesoporous apatite microspheres obtained by chemical immersion method have irregular shape, and the nitrogen adsorption-desorption isotherms are identified as type IV isotherms with type H₃ hysteresis loops. The mesoporous structure is unimodal with the pore size of 3.9 nm. However, the mesoporous apatite microspheres converted from calcium carbonate microspheres in a cetyltrimethylammonium bromide （CTAB）/Na2HPO4 solution/cyclohexane/n- butanol emulsion system are monodispersed with the particle size of ⁵μm. The mesoprous structure is bimodal with the pore size of 3.9 nm and 9.0 nm. With increasing the reaction time and improving the temperature, the bigger mesopores begin to disappear. The formation mechanism of mesopores with the pore size of 3.9 nm is attributed to the aggregation of nanoparticles, and that of 9.0 nm is attributed to the CTAB micelles served as templates.Mesoporous apatite coatings were fabricated by electrophoretic depositon- chemical immersion method. This method consists of a two-stage application route: the deposition of nacre powders or CaCO3 powders on Ti6Al4V substrates by electrophoresis, and the conversion of nacre coatings or CaCO3 coatings to apatite coating by treatment with PBS. After soaking nacre coatings or CaCO3 coatings in PBS for 1 day, plate-like apatite coatings with mesoporous structure are formed. The pore sizes are distributed around 3.9 nm. After soaking for 9 days, the plate-like structure is turned into a sponge-like structure, and the mesopores partially disappear. A TiO_x layer and PO₄^3- ions appear on the Ti6Al4V substrate surfaces by pretreatment with a H₃PO4/HF solution. The TiO_x and PO₄^3- ions can induce the formation of apatite crystals, resulting in a composition gradient in the TiO_x layer. Simulated body fluid （SBF） immersion tests reveal that the calcium deficiencies in apatite lattice, the mesoporous structure, and nacre organic materials can improve the in vitro apatite forming ability of the mesoporous apatite coatings.Magnetic mesoporous apatite coatings were fabricated by electrophoretic deposition of CaCO₃/Fe₃O₄ particles on Ti6Al4V substrates followed by treatment with PBS at 37°C. After soaking CaCO₃/Fe₃O₄ coatings in PBS, apatite nucleates heterogeneously on the surfaces of CaCO₃/Fe₃O₄ particles and forms a plate-like structure. Fe₃O₄ increases the velocity of nucleus formation of apatite. After soaking for 1 day, the percentage of unreacted calcium carbonate is 9.1%, lower than the 41.0% for apatite coatings without magnetism. The pore size of mesopores is distributed around 3.9 nm, and the mesopores do not disappear after treatment with PBS for 9 days. SBF immersion tests reveal that Fe₃O₄ improves the in vitro apatite forming ability of biocoatings.更多还原