【作者】 邱进俊；

【导师】 郑启新； 刘承美；

【作者基本信息】 华中科技大学 ， 生物医学工程， 2006， 博士

【摘要】 通过非侵害和微创方式修复骨缺损,具有组织损伤小、操作简单、手术并发症少等优点。聚磷酸酯具有良好的生物相容性和生物可降解性能,而且其主链中柔软的磷酸酯键赋予聚磷酸酯较低的玻璃化转变温度,常温下具有可注射性。因此,本文首次探索将聚磷酸酯应用于可注射性骨修复材料的可行性。本文以富马酸二(1,2-丙二醇)酯与二氯磷酸乙酯为单体,首次设计并制备了新型主链重复结构单元中含双键的不饱和聚磷酸酯,并改进了单体富马酸二(1,2-丙二醇)酯的合成方法,显著提高了单体的纯度与产率,同时缩短了反应时间,减少了环氧丙烷的用量。GC-MS以及NMR分析表明单体富马酸二(1,2-丙二醇)酯中具有三种异构体导致聚磷酸酯主链中存在三种链接顺序。所制备的三种分子量( M w=3198 g/mol,4044 g/mol,5956 g/mol)的聚磷酸酯具有较低的玻璃化温度,在100℃下热稳定性能较好。不饱和聚磷酸酯主链中的双键可以与N-乙烯基吡咯烷酮(NVP)、甲基丙烯酸2-羟乙酯等乙烯基单体通过热引发共聚交联,形成三维交联网络,也可通过光引发交联,但光引发交联深度受到限制。不饱和聚磷酸酯、N-乙烯基吡咯烷酮以及与β-磷酸钙复合后的浆料具有良好的可注射性能,以过氧化苯甲酰/N,N-二甲基对甲基苯胺氧化还原体系引发浆料的交联反应,原位构建了骨组织工程支架材料。由交联反应温度曲线的测定,确定交联体系原位固化时的最高交联温度为46.49～93.07℃,固化时间为1.7～10.3 min。固化后复合物的最大压缩强度以及最大压缩模量分别为94.36±6.96 MPa及2096.93±92.86 MPa,力学强度在松质骨和密质骨之间。交联固化时间、最高交联温度与复合物的力学强度可以通过改变交联体系中各组分的含量以及聚磷酸酯的分子量来调节。交联固化后复合物的体外降解分为两个阶段,第一阶段(48小时内)以N-乙烯基吡咯烷酮以及聚N-乙烯基吡咯烷酮的快速溶出为主,材料的力学性能、质量保持率迅速降低,而体积由于溶胀作用快速增大;第二阶段的降解主要由聚磷酸酯的水解作用引起,降解较平缓。增加聚磷酸酯的分子量以及用量有助于保持材料在降解中的力学性能并减小失重率。β-磷酸钙能够减小材料在降解过程中的体积变化以及失重率,同时提高材料的力学稳定性。降解120天后,复合物的最大压缩强度与压缩模量分别为1.21 MPa和15.10 MPa,低于松质骨强度。不饱和聚磷酸酯/N-乙烯基吡咯烷酮交联网络的药物释放性能受药物溶出行为以及材料的降解共同控制,减少交联反应时N-乙烯基吡咯烷酮的用量以及使用较高分子量的聚磷酸酯都能够减缓药物释放的速度。在聚合物基材上制备了钙-磷涂层以提高交联聚磷酸酯的成骨活性,同时得到了一种中空结构的管状钙-磷纤维,管壁由磷酸钙片状晶体聚集而成,纤维直径在2～50μm之间,纤维的生长发生在纤维的顶端。采用鼠肌肉内植入硬组织材料的动物模型,进行了组织形态学的观察,对交联聚磷酸酯/β-磷酸钙复合材料的生物相容性能的初步研究表明:复合材料具有良好的生物相容性能,在体内可降解,并具有一定的异位成骨活性。通过对不饱和聚磷酸酯的原位交联反应特性、光引发交联反应性能、可注射性能,交联后复合物的机械性能、降解性能、释药性能以及生物相容性等性能的初步评价,不饱和聚磷酸酯可以应用于可注射性骨修复材料。更多还原

【Abstract】 Injectable bone repair biomaterials have been developed because they can fill irregularly shaped defects and may allow bone augmentation, both with minimal surgical intervention. These injectable biomaterials could crosslink in situ to form a three dimensional network with suitable properties. Polyphosphoesters are analogs of nucleic and teichoic acids with excellent biodegradability and biocompatibility. The phosphoester bond in the polyphosphoester backbone can be cleaved by water and possibly enzymatic digestion under physiological conditions. The flexible P-O-C bonds in the backbone make polyphosphoesters commonly with low glass transition temperature and show poor mechanical strength in physiological temperature. In this work, in order to improve mechanical property of polyphosphoesters and meet the demand of bone repair materials, a novel crosslinkable polyphosphoester based on bis(1,2-propylene glycol) fumarate(BPGF) and ethyl dichlorophosphate was designed which contained unsaturated double bonds in backbone.The monomer BPGF was synthesized by a new method without any solvent. Purity and yield of BPGF were both rose remarkably comparing with the reported method. Three possible bonding models in polyphosphoester chain resulting from three isomers of bis(1,2-propylene glycol) fumarate was confirmed by NMR and GC-MS spectra. Unsaturated polyphosphoester(UPPE) can be crosslinked through the double bonds along with its backbone. Vinyl monomer, such as N-vinyl pyrrolidone(NVP) and 2-hydroxyethyl methacrylate can be used as crosslink agent. Polymer network formed by UPPE and NVP through in situ crosslinking reaction initiated by BPO-DMT system. For all formulations, the maximum crosslinking temperature was between 46.49 to 93.07℃which was lower than that of 97℃for poly(methyl methacrylate) bone cement. The setting time was between 1.7 to 10.3 minutes, and strongly affected by BPO/UPPE ratio. Maximum compressive strength and compressive modulus values of crosslinked UPPE/β-tricalcium phosphate composite were 94.36±6.96 MP and 2096.93±92.86 MPa, which were higher than those of human trabecular bone.In order to control polymerization exotherm and facilitate the operating conditions, the crosslinking reaction of UPPE and NVP initiated by UV light has also been investigated. Results show that the gel content of curing product was remarkably improved by addition of photoinitiators The gel content of crosslinked network obtained from UPPE with Mw=4040 g/mol is lower than that of with higher molecular weight when the irradiation time was less than 2 minutes, but an opposite results would obtained by extending irradiation time. The surface layer of sample absorbed the UV light and decreased the photocrosslink reaction rate of the deep layer.Weight and mechanical strength of all formulations were decreased rapidly within the first two days during degradation experiment. Following the first stage, very slowly decreased in weight and mechanical strength was observed during the remaining degradation time. Increasing UPPE molecular weight andβ-tricalcium phosphate incorporation resulted in an increase in both compressive strength and compressive modulus, and a decrease in weight loss.In order to improve the osteoconductivity, a simple process was developed to deposit a mineral layer on the surface of crosslinked UPPE. It was found that mineral fibrous grown upwards from the surface of crosslinked UPPE. Composition of fibre was calcium deficient carbonated apatite with low crystallinity. SEM micrograph indicated that the fibre had a hollow tubing structure and the tube wall was a flakelike assembly. The growth was at the tip of the fibre at a rate about 0.5mm/min and reached several centimeters in length after 2 hours.Crosslinked UPPE/β-tricalcium phosphate composites exhibited good biocompatibility and no deleterious long-term inflammatory response when be implanted subcutaneously in rats.更多还原