【作者】 梁列峰；

【导师】 翁杰；

【作者基本信息】 西南交通大学 ， 材料学， 2009， 博士

【摘要】 组织工程的核心是用具有生物活性、可生物降解的聚合物为材料在体内或体外构建可支持组织细胞生长、增殖、迁移、黏附的支架。骨组织工程支架具备骨诱导、骨植入等功能,在骨生长和再生期给予足够的力学强度以维系结构的稳定。支架具有多孔形态,孔隙率和连通性是其性能的重要参数,孔隙率较大支架有利于更多的骨细胞的生长,但本身强度有所降低。羟基磷灰石(Hydroxyapatite, HA)存在于人体硬组织如骨和齿中,在骨组织替代中已取得成功应用。多孔HA其内部结构满足细胞向内部渗透、迁移、黏附和生长的条件。早期研究表明,相对于细胞尺寸,细胞移植和传递的基本要求是支架孔隙最小孔径至少要100μm以上,宏观孔隙的孔径需大于300μm。本研究重点在于HA多孔陶瓷制备及其对材料性能影响,研究对支架微孔形貌的有效控制方式,使支架内连通与抗压强度均衡与优化,对成型后样品的孔隙形貌,孔隙尺寸,孔隙分布、孔隙间连通观测,分析和推断成孔方法与多孔陶瓷结构特征与其抗压强度的关系,用X射线衍射图谱(XRD)对样品进行物相分析；测试样品的抗压强度,确定可调控多孔形态特征、具有高贯通性并满足力学特性的多孔HA陶瓷制备方法：1.甲壳素作载体制备三维多孔HA陶瓷多孔植入体要满足骨细胞进入,最小孔径一般要在200μm以上。有资料表明孔隙连通在骨传导过程中所起的作用超过了孔隙本身。实验初期使用甲壳素做粘结剂,载入HA料浆,筛选出适宜的甲壳素使用浓度和成孔方式和成孔物质,选定水溶性蔗糖作为制孔剂,制备孔隙率和孔径可控的HA陶瓷,表征孔隙的形态、大小及分布,使用XRD技术分析样品结晶结构和化学成分；为增强多孔陶瓷内的孔道连通,对半烧结陶瓷体进行酸蚀刻扩孔。采用不同LiCl含量,制备HA陶瓷样品,研究添加助剂改善多孔HA陶瓷抗压强度的可行性,实验表明掺杂后的HA陶瓷耐酸蚀能力增强,HA陶瓷致密度提高,微气孔减少,掺杂的HA陶瓷显微硬度有所提高,X射线衍射分析验证LiCl的少量引入没有导致HA的分解。实验采用二甲基乙酰胺／氯化锂(DMAc/LiCl)和聚乙烯醇两种陶瓷配浆体系,成管芯体吸附HA料浆,采用初坯芯体抽离或烧结过程燃烧挥发制备HA陶瓷管,获得具有期望形貌特征的HA陶瓷管。本实验重点研究多孔HA陶瓷孔隙间连通的增强方法,确定HA陶瓷成孔与孔隙间贯通的调控方法。2.纤维织入构建高贯通多孔生物陶瓷对纤维纱线采用高分子胶液表面涂层,保持表面纹路,并以此作陶瓷体内隧道的支撑体；选择聚乙烯醇／羟基磷灰石粉(PVA/HA)作为陶瓷料浆,与纤维纱线同步织入模具形成陶瓷初坯,纱线在坯体内呈定向排列；根据纱线预处理、纤维成分和坯体组分确定烧结工艺；观察表明陶瓷体内孔道直通,孔道内表面形成细微条纹,有一定的粗糙度,孔道分布均匀,孔隙率、孔隙尺寸和分布均满足多孔生物陶瓷的综合要求。3.HA纤维的制备及其多孔陶瓷的自充填初期研究借助于蚕丝纤维理化性质,使HA浆料粘附于蚕丝纤维上后并固化,烧结制备出HA陶瓷短纤维。采用DMAc/LiCl/Chitin/HA溶胶-凝胶体系批量制备HA纤维,纤维直径、纤维形貌特征主要受HA粉粒尺寸、凝固浴温度及流速、相对于纺丝液的丝流流向、烧结工艺中恒温区的选择以及烧结温度的影响,实验获得了直径在100-150μm、连续长度的HA陶瓷纤维。研究进一步设计了一种由HA粉体和HA短纤维制成多孔HA陶瓷的方法,通过改变添加的制孔剂和纤维的数量,可制备气孔率在60%-80%的三维支架。4.多孔HA陶瓷抗压强度的影响因素分析对采用的各种方法批量制作的HA多孔陶瓷的抗压强度进行了测试与分析,结果发现：多孔陶瓷经酸蚀刻后,抗压能力减小；同一气孔率范围内,样品抗压强度的变异系数随气孔率增大而增大；制备低气孔率(<70%)多孔陶瓷时,定向纤维织入法获得的孔隙率、孔径及分布、孔隙分布实现优化,当气孔率>70%后,精密控制纤维纱线排列密度能保证支架结构的均衡；制备高孔隙率多孔HA陶瓷体物料颗粒宜应采用10μm以下粒径,适当提高烧结温度能提高多孔陶瓷整体强度；纤维自增强型多孔陶瓷在一定气孔率范围内实现了增强效果,以开气孔率为基准,抗压能力提高效果显著,该方法适宜制备气孔率在80%以下的多孔HA陶瓷。更多还原

【Abstract】 The key of tissue engineering is manufacturing a bioactive and biodegradation scaffold to either maintain existing tissue structures or enable tissue growth for supporting growth, proliferation, transplanting and adhering of tissue cell. The scaffold must be osteoconductive and osteointegrative, and have enough mechanical strength to provide structural support during the bone growth and remodeling. All kinds of the scaffold are porous materials. The porosity and interconnectivity are important factors for the scaffold and also is propitious to more bone cell growth, the intensity of reconstructing bone has higher strength but that of the scaffold itself should reduce on the contrary.Hydroxyapatite (HA, Ca10(PO4)6(OH)2) is found in hard tissues of the body such as bone and teeth, has had some success as a bone replacement material.The porous HA ceramic should fulfil requests about tissue cells penetrating, transplanting, adhering and developing. The structural property of porous HA is more resorbable and more osteoconductive than dense HA.Based on early studies, the minimum requirement for pore size is considered to be～100μm due to cell size, migration requirements and transport. However, pore sizes >300μm are recommended, due to enhanced new bone formation.Some new techniques of fabricating porous HA ceramic scaffolds are introduced in this study. Comparing the samples manufactured and trying to discover the method about technique on preparation of porous ceramic with higher interconnection and favorable strength and also being controlled artificially. The shape, size, distributing, interconnecting of pores in samples were observed by Scanning electron micrograph. XRD patterns of sample indicated that the samples produced have no introduced heterogeneity and security of the techniques. The mechanical parameters of the samples were test by mechanical universal testing machine. The technique to manufacture porous HA ceramic with high interconnectivity and satisfied for mechanical performance was ensured besides the configuration of samples may be controlled artificially.1. The preparation of porous 3-D HA ceramic using chitin for carrier.It was claimed that a minimum pore size of (?)200μm was necessary for bone ingrowth into the porous implant materials. It is suspected that the size of interconnection is the main limiting factor of osteoconduction rather than the size of the pores themselves.In initial experiment, the ceramic slurry was prepared by chitin used as carrier, Hydroxyapatite ceramics with controlled porosity and pore size were prepared by adding sugar particles as pore-making agent (PMA). The scaffolds prepared have an open, uniform and interconnected porous structure. The pore morphology was characterized using a scanning electron microscope and light microscopy. The porosity and rate of open pore were measured for a series of samples. Two kinds of acid as corrosive agent to HA were respectively used to outspread the windows between pores within half-sintered blocks. It was found that LiCl has an effect on densification of HA ceramic during sintering. Micro rigidity of the HA ceramic doped has increased and changed steadily in different testing point. XRD patterns indicated the introducing of LiCl has no resulted decomposing of HA. The transport of cells in porous ceramic represent directional. Two kinds of slurry preparation, DMAc/LiCl/CT/HA and PVA/HA, were used for forming HA ceramic tube with using different core stick to conglutinate the slurry. SEM indicated the two slurry forming system could result distinctly in various appearances to HA tube. The techniques about improving interconnectivity between pores within porous HA ceramic blocks has become emphases of the experiment. Every factor of influencing on pore forming and linking among pores of the fabricated porous HA ceramic and artificially controlling method of inner structure were analysed.2. Fabricating porous bioceramics with interconnectivity by fibers pre-treated.Fibre yarns pre-treated coated by special macromolecule glue were weaved into mould with HA slurry blending with Polyvinyl Alcohol (PVA) to fabricate porous bioceramic. Stripe saved on surface of fiber was expressly charactered on channel in the ceramic block. SEM micrographs showed that channels have directional connecting, distributing equally, intact configuration and existence of thin stripes on inner-face. XRD patterns indicated the crystalline structure.The results indicated that the solidified fiber yarn could establish channel or pore in porous bioceramic. The structure should satisfy request about tissue engineering scaffold.3. Study on the process for modeling hydroxyapatite ceramic fiber and fabricating the porous ceramic by fiber self-filling.Hydroxyapatite slurry were adhere to surface of silk and simultaneously to be consolidated. The short HA ceramic fibres with preferable tropism were prepared through reasonable design of sintering process. N. N. Dimethyl Acetamide, LiCl and chitin were used for preparation of sol-gel systems of spinning fluid blended HA powder to make initial fiber. The concentration of each component of spinning fluid, the size of HA powders, temperature and flow speed of solidification bath would influence to fiber configuration and diameter. These infection factors also include the temperature of sintering process and confirming area of constant temperature. The experiment obtained fiber with diameter of 100-150μm and sequential length. On second thoughts, the method of fabricating porous HA ceramic by using HA powders and short HA fiber. By changing amount of fiber and pore-forming agent, Porous HA ceramic with porosities ranging from 60% to 80% were produced.4.The analysis about influence of mechanical performance to porous HA ceramic.The test and analysis on mechanical performance to porous HA ceramic samples manufactured by various methods were carried. The results showed that the strength of porous block etched by acid had reduced. Variation coefficient of strengths among the samples with same porosity increased along with porosity. Porosity, size and distribution of pores and channels in ceramic block made from directional fiber were optimized in the condition of low porosity. Arrange consistency of fiber yarn should be controlled well and truly when the porosity is over 70%. The size of HA powder should be less than 10μm when the HA ceramics with high porosity were required. Increasing sintering temperature can enhance the strength of whole porous ceramic block. The porous block filled by HA fiber actualized strength enhancing at certain porosity and the effect of strength increasing was very obvious standing open pore ratio. The method suits for preparation of porous HA ceramic with porosity of less than 80%.更多还原