【作者】 胡巧玲；

【导师】 沈家骢；

【作者基本信息】 浙江大学 ， 材料学， 2004， 博士

【摘要】 本论文是在研究和分析了大量生物体结构的基础上，认为层状叠加结构是自然界绝大多数生物体的内在结构之一，提出仿木年轮结构作为本研究的基本思路。以自然界生物体中普遍存在的壳聚糖为基本原料，根据膜渗透原理，建立了原位沉析技术，将壳聚糖自组装成具有仿树木年轮层状叠加结构的基本骨架材料。在这个骨架材料的基础上，以不同的方法进行组装，利用就地反应羟基磷灰石与壳聚糖纳米复合，制得具有不同仿生结构和具有不同功能的可降解的能促进骨修复的骨科材料。 1．建立了原位沉析法制备仿木年轮壳聚糖骨架材料。将壳聚糖溶液在模具里浇铸成膜，制得微孔壳聚糖渗透膜。将壳聚糖酸溶液放在膜内，碱性NaOH凝固液放在膜外，通过膜渗透，壳聚糖沉析组装成层状叠加的凝胶棒。探索壳聚糖溶液的浓度、不同的碱浓度、温度对凝胶棒的层厚、层间距及形成速度的影响。从Liesegang环得到启示，合理地理解和解释了壳聚糖在成型过程中自行组装成同心筒状的层层叠加结构的机理，用间歇沉析法、梯度沉析法有效地调控结构。结果表明：原位沉析法就是利用NaOH溶液与壳聚糖分子上的-NH₃⁺起酸碱中和反应，使壳聚糖分子在模板上原位沉积成三维层状壳聚糖凝胶棒。 2．对壳聚糖棒材分子量、结晶度、吸水性进行了表征，发现在成型过程中壳聚糖分子量下降很少，结晶度降低，而棒材吸水性仍较强。从原位沉析法的制备过程、棒材断裂面的裂纹和形态分析表明原位沉析法制备的壳聚糖棒材是径向、纵向取向，各向异性的。 3．对壳聚糖棒材的力学强度进行了测试，并分别讨论了原料、含水量对棒材力学性能的影响。在相同的脱乙酰度下，分子量越大，壳聚糖棒材力学强度相应提高。当含水量较低时，棒材具有较大的力学强度，随着含水量增加，其力学强度下降较快。 4．针对壳聚糖棒材在湿态环境下力学性能衰减速率过快的问题，提出了模仿荷叶的疏水结构对壳聚糖表面进行结构修饰的思路。首先对壳聚糖棒材表面进行酰化，制得一层类同于荷叶微观凹凸的表面结构，并在此结构的基础上再涂以一层生物酯，以达到天然生物材料的疏水效果。通过对壳聚糖各种化学改性方法的比较，最终选定了壳聚糖材脚红大笋溥士笋少居戈^口00刃掇歹料表面的乙酞化。实验结果表明:壳聚糖棒材表面经过乙酞化试剂的作用，经SEM观察，发现原壳聚糖棒材平滑的表面变得粗糙。经接触角实验和吸水速率测试表明:壳聚糖棒材的表面经酞化改性后，降低了材料表面的极性，从而降低了材料的亲水性。并且通过控制酞化反应时间，能有效的增大棒材的接触角，能与最外层的生物酷涂层紧密结合，经模拟体液浸泡实验，该材料三个月内具有较好疏水作用，达到了预期的目的。 5.采用原位复合方法制备了高性能的壳聚糖/轻基磷灰石纳米复合材料。根据轻基磷灰石在酸性条件下不能形成而在碱性条件下才能形成的原理，采用预先沉积的壳聚糖膜将含有轻基磷灰石前驱体的壳聚糖酸溶液与凝固液隔离。该膜同时控制壳聚糖沉积与轻基磷灰石前驱体转化为轻基磷灰石的过程，使其缓慢且有序地进行。当pH值改变时，质子化的壳聚糖分子链在负电层诱导下有序沉积并形成层状结构与轻基磷灰石原位生成，并实现二者纳米级复合。XRD，T甜结果分别证实原位生成的磷酸盐是轻基磷灰石，且轻基磷灰石颗粒长约为100nm，宽30⁵0lun。SEM结果表明用原位复合方法制备的材料具有层状结构。用原位复合的方法制备的CS/HA（100/5，质量比）纳米复合材料弯曲强度高达86MPa，比松质骨高3⁴倍，该材料有望用于可承重部位的骨修复材料。更多还原

【Abstract】 On the basis of analysis and study of the quantities of the biology body structure, especially the structure of the nacre , bone, wood and bamboo stem et al, it’s found that the layer structure plays an important role in their excellent mechanical propertities. To obtain the layer stucture mimicking the layer structure of wood, so-called annual ring structure, is the goal of the study. Chitosan(CS), abundant in nature derivated from chitin highly deacelylation, has excellent biocompatibility and bioactivities. While chitosan, insolubility and apt to oxidation, was limited as structure materials due to the difficulty of processing. Strong intro- and inter- molecular H-bond is responsible for its insoluble in water and active C2- NH2 is responsible for its instability at high temperature. In this study, in-situ precipitation method was developed to preparation chitosan rod by using chitosan membrane as template and NaOH as precipitant. The congealed chitosan rod was mildly auto-assembled into 3-D concentric layer by layer structure, similar to the annual ring structure of wood, when NaOH solution penetrated the chitosan membrane. The dried chitosan rod has excellent properties. Furthermore, hydroxyapatite(HA), a bioabsorble, biocompatible and osteoinductive materials, was introduced into the process of preparation and the congealed CS/HA rod was prepared via in-situ compositing route. The dried CS/HA nanocomposites has even better mechanical properties than pure chitosan rod. HA in chitosan matrix will also exert some sort of effct on the bioactivity and the bone-bonding ability of CS/HA composites when composits was implanted as bone substitute.1. Using chitosan membrane as template and NaOH as precipitant, in-situ precipitation method was developed to prepare chitosan rod. Molding mechanism of CS congealation rod and the effects of base concentration, CS concentration and temperature on the molding were studied. The results showed that in the process of in-situ precipitation CS was precipitated layer-by-layer in the template and then formed 3D layer CS congeal rod through acid-base neutralization of NaOH and the amino group of CS. The process conditions being well controlled, the congealed rod formed homogeneous structure.2. Molecular weight, crystallinity and water absorption of CS before and after process were studied. It was found that the preparation process had little influence on the CS molecular weight. The crystallization of the chitosan rod decreased but water absorption of CS rod wasstill large. Morphology investigations indicated that CS rod prepared by in-situ precipitation was bi-axis oriented with the property of anistropy.3. Mechanical strength of CS rod was tested and the effects of raw material and water content of CS rod were discussed. The results showed that mechanical strength of CS rod was improved as molecular weight increased with the same D.D. CS rod had good mechanical strength in dry state but mechanical strength decreased greatly as water content increased.4. The CS/HA nanocomposite with high performance were prepared via in-situ compositing route. The key of in-situ compositing is to pre-precipitate CS membrane which was used to obstruct the CS/HA precursor from NaOH aqueous solution. The CS membrane controlled the process of CS precipitation and transformation of HA from the precursor due to the change of pH simultaneously and tardily. XRD was carried out to determine the component of CS/HA composite. TEM and SEM were performed to investigate the morphology of HA granules and CS/HA composite. Results showed that the in-situ formed calcium phosphate in CS was exactly HA, and that nano-size HA granules (30-50nm width, l00nm length) were dispersed in CS matrix uniformly. The result of SEM showed that the structure of CS/HA composite prepared by in-situ compositing is layer-by-layer structure, which can further prove the mechanism of in-situ compositing. The mechanical properties of CS/HA were evaluated by the three point bending test. The bending strength and modulu更多还原