原位生长法制备羟基磷灰石增强聚乙烯醇形状记忆复合材料

发布时间：2018-08-01 08:18

【摘要】：聚乙烯醇(PVA)水凝胶具有弹性高、化学性质稳定、易于成型、无毒副作用及良好的生物相容性,在生物医学领域具有广泛的应用,如作为缓释载体、组织工程支架、人工器官、人工软骨等。作为智能材料的一种,自从发现PVA具备形状记忆效应后,在过去的15年中PVA在很多领域得到了发展。这种热致感应型形状记忆性高分子凝胶在药物缓释,仿生材料(动物的肌肉体系也是一个智能型聚合物凝胶体系,通过肌肉的收缩与舒张可以把化学能转化为机械能),智能控制等领域具有许多潜在的应用价值。但是,此类材料最重要的缺陷就是力学性能差,制约了它在生物医用方面的发展。为了改善其力学性能,很多研究者探索并实践了各种途径,在保持材料生物活性的前提下提高其力学性能。例如：采用不同交联方法制备PVA凝胶、对基体PVA改性或构建无机粒子增强的PVA复合材料。目的都为一个：保证良好的生物相容性、提供适宜的力学性能,使其更好更广的被应用,更快更早的为医疗所需为人类服务。以此为出发点,本论文进行了下面的探索性实验。实验中选取以羟基磷灰石(HA)为无机粒子,构建HA/PVA形状记忆复合材料,以改善形状记忆PVA水凝胶的力学性能。HA属于生物陶瓷,其化学成份和晶体结构与脊椎动物的牙齿、骨组织中的无机成分相似,具有优良的生物亲和性,与骨组织极易结合,生物相容性好,更重要的是对人体组织无任何的毒副作用。实验采用一种新的原位生长法制备形状记忆HA/PVA复合材料,并对材料的结构和性能以及均一性进行了分析,从分子上探讨了HA均匀形核的机理,探讨复合材料的形状记忆性能,考察复合材料的形状记忆特性参数,探究复合材料的形状记忆机理。其主要结论如下： 1.采用原位生长法制备了形状记忆HA/PVA复合材料,并对复合材料的结构和性能进行了表征。结果显示：添加氨水矿化结晶的过程中,凝胶中矿化结晶的无机粒子为HA粒子,直径大约1μm,均匀的分散在PVA基体中,且具有毛刺状的微观结构。复合材料的力学强度以及热稳定性随着HA含量的增加而得到改善。 2.对材料的均一性进行了分析,证明了材料具备良好的均一性。实验过程中,PVA溶液中所添加的HA粉体溶解所产生的Ca2+和PVA分子中的羟基之间形成一种配位结构,形成螯合物。当凝胶交联完全,加入氨水矿化结晶时,Ca2+和PO43-很少向氨水中扩散,几乎所有的Ca2+和PO43都嵌入凝胶中,在凝胶中原位形核长大。 3.探讨复合材料的形状记忆性能,考察复合材料的形状记忆特性参数,探究复合材料的形状记忆机理。所有复合比的凝胶试样都在室温中晾干至常量后,形状记忆行为的实验结果显示,不同复合比例的HA/PVA复合材料都表现出了令人满意的形状记忆效应,复合材料的形状固定率都在93%以上,形状记忆回复率都是在90%左右；材料的回复温度在Tg以上时,复合材料回复速率加快；复合材料大概在40S左右都能回复完全,循环形状记忆实验表明复合材料具有良好的循环利用价值。 4.体外细胞实验中发现HA在PVA凝胶中的原位生长改善了复合材料的生物相容性,表现为更好的成骨细胞黏附以及细胞增殖活性。
[Abstract]:Polyvinyl alcohol (PVA) hydrogels have high elasticity, stable chemical properties, easy to form, non-toxic side effects and good biocompatibility. It is widely used in the biomedical field, such as a sustained-release carrier, tissue engineering scaffold, artificial organ, artificial cartilage and so on. As one of the intelligent materials, the shape memory effect of PVA has been found. In the past 15 years, PVA has developed in many fields. This thermo induced shape memory polymer gel is controlled by drug release. Biomimetic materials (the animal's muscle system is also an intelligent polymer gel system, through muscle contraction and relaxation can convert chemical energy into mechanical energy), intelligent control and other fields. Many potential applications. However, the most important defect of this kind of material is the poor mechanical performance, which restricts its development in biology and medicine. In order to improve its mechanical properties, many researchers have explored and practiced various ways to improve their mechanical properties on the premise of maintaining the biological activity of the materials. For example, the use of different crosslinking methods. The preparation of PVA gels, the modification of matrix PVA or the construction of PVA composites reinforced with inorganic particles. The aim is to guarantee good biocompatibility, provide suitable mechanical properties, make it better and more widely used, and serve the human being faster and earlier for medical treatment.
In the experiment, hydroxyapatite (HA) was selected as inorganic particle to construct HA/PVA shape memory composite to improve the mechanical properties of shape memory PVA hydrogel,.HA belongs to bioceramics. Its chemical composition and crystal structure are similar to the inorganic components in the teeth of vertebrates and bone tissue, with excellent biological affinity and very easy to bone tissue. The combination, good biocompatibility, and more important is no toxic and side effects on human tissues. A new in situ growth method was used to prepare shape memory HA/PVA composite. The structure, properties and homogeneity of the material were analyzed. The mechanism of HA homogeneous nucleation was discussed and the shape memory of the composite was discussed. It is possible to investigate the shape memory properties of composite materials and explore the mechanism of shape memory.
1. the shape memory HA/PVA composites were prepared by in situ growth method, and the structure and properties of the composites were characterized. The results showed that in the process of adding the mineralized crystallization of the ammonia water, the mineralized and crystallized inorganic particles in the gel were HA particles, the diameter was about 1 m, and the particles were dispersed in the PVA matrix and had the burr like microstructure. The mechanical strength and thermal stability of the composites improved with the increase of HA content.
2. the homogeneity of the material was analyzed, which proved that the material had good homogeneity. During the experiment, a kind of coordination structure was formed between the Ca2+ and the hydroxyl groups in the PVA molecule produced by the dissolution of HA powder in the PVA solution. When the gel was crosslinked completely and added into the mineralized crystallization of the ammonia water, the Ca2+ and PO43- rarely moved to the ammonia water. Almost all Ca2+ and PO43 were embedded in the gel, and grew in the gel in situ.
3. the shape memory properties of composite materials are investigated, and the shape memory properties of the composites are investigated and the shape memory mechanism of the composites is explored. All the composite gel specimens are dried to the constant at room temperature. The experimental results of shape memory behavior show that the HA/PVA composites with different composite ratios are satisfactory. The shape memory effect of the composite is more than 93%, and the recovery rate of shape memory is about 90%. When the recovery temperature of the material is above Tg, the recovery rate of the composite is accelerated, and the composite material can be recovered around 40S. The cyclic shape memory experiment shows that the composite has a good recycling use. Value.
4. in vitro cell experiment, it was found that the in situ growth of HA in PVA gel improved the biocompatibility of the composite, which showed better osteoblast adhesion and cell proliferation activity.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TB332

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