【作者】 王征科；

【导师】 胡巧玲；

【作者基本信息】 浙江大学 ， 材料学， 2009， 博士

【摘要】 可生物降解的三维壳聚糖骨折内固定材料可避免其他种类骨折内固定装置的二次手术、应力遮挡、非菌性炎症反应等缺点。为了满足三维壳聚糖棒材在骨折临床使用中的要求，本论文采用多种方法增强改性壳聚糖棒材并研究了增强改性的机理。高强度的壳聚糖接骨棒、接骨钉将是一种新型的、具有自主知识产权的生物医用材料，对减轻骨折病人痛苦、节省医疗费用具有重要意义。(1)利用甲壳素和壳聚糖脱乙酰度的差异导致两者在稀酸水溶液中溶解性能的不同，制备了具有层状叠加结构的甲壳素纤维／壳聚糖三维复合棒材，当复合棒材受载荷作用时，应力由壳聚糖基体传递给纤维增强体，从而实现增强改性的目的。滤纸纤维表面粗糙，增强了纤维与壳聚糖基体之间的机械铆合力，并且两者发生了界面化学反应，生成了希夫碱，有效地增加了复合材料的界面结合力，从而提高了复合棒材的力学性能。采用聚对胺苯乙炔包覆多壁碳纳米管，使多壁碳纳米管均匀分散在壳聚糖基体中，可有效承担载荷。另外，给多壁碳纳米管穿上一层水溶性、磁性“外套”，在磁场的诱导下实现了多壁碳纳米管在壳聚糖基体中均匀分散、平行有序排列。(2)以海藻酸钠、羧化壳聚糖聚阴离子电解质改性三维壳聚糖棒材，壳聚糖分子链上的氨基、乙酰胺基与聚阴离子电解质的羧酸盐官能团之间存在很强的静电相互作用，使材料变得更加紧密，从而改善了复合棒材的力学性能。(3)通过仿生设计制得了高强度的多聚磷酸钠／壳聚糖三维复合棒材，棒材的仿木年轮层状叠加结构属于Liesegang Ring现象；棒材的仿竹空心结构可以通过控制壳聚糖溶液在碱液中的凝固时间来实现；多聚磷酸钠与壳聚糖之间存在强的静电相互作用以及氢键作用，使得壳聚糖基体变得更加紧密。层状叠加结构、仿竹中空结构以及复合棒材中的静电相互作用三者共同作用，大幅度提高了棒材的力学性能。(4) Co60-γ-rays辐射引起了壳聚糖分子的断链反应，降低了壳聚糖的分子量，使得壳聚糖分子链间的缠结作用减弱，链段运动能力增强，有利于壳聚糖分子的结晶重排，提高壳聚糖的结晶度，从而提高壳聚糖棒材的强度。微波辐射产生热效应，使壳聚糖棒材发生热交联反应，形成体型网络状结构，提高了壳聚糖棒材的力学强度。(5)戊二醛交联改性壳聚糖棒材及羟基磷灰石／壳聚糖三维复合板材，使壳聚糖基体形成体型网络状交联结构，棒材的层状叠加结构变得更加紧密，纳米羟基磷灰石颗粒尺寸减小。壳聚糖棒材受应力作用后产生的裂纹在一层内扩展，当遇到另外一层时发生钝化，或发生偏转，改变扩展方向，沿着层与层之间撕裂，吸收能量。交联壳聚糖棒材的层状叠加结构变得更加紧密，因而应力沿层间撕裂需要消耗更多的能量。戊二醛交联壳聚糖的体型网络状结构以及层状结构的裂纹扩展机制是棒材力学性能提高的原因。通过本课题的研究使三维壳聚糖棒材的力学性能得到了很大的提高，从增强改性的效果来看，多聚磷酸钠／壳聚糖仿生中空棒材、微波辐射改性的壳聚糖棒材以及戊二醛交联改性的壳聚糖棒材力学性能较好，此三种方法使棒材的弯曲强度达到180 MPa左右，约为纯壳聚糖棒材弯曲强度的两倍，可望用于临床骨折内固定。更多还原

【Abstract】 Three dimensional chitosan rod is one kind of biocompatible and biodegradablematerial, which could be used for internal fixation of bone fracture and could avoidsome defects of metallic material and PLA screws, such as second operation toremove the implant, stress-shielding phenomenon, aseptic inflammation caused byacid degradation products, and so on. To meet the demand for the clinical bonefracture internal fixation, several strategies have been used for reinforcing chitosanrods, and the reinforcement mechanisms also have been studied in this research.（1） Chitosan could be dissolved in acetic acid aqueous solution, but chitin fibercould not be dissolved, due to the different deacetylation degree, so chitin fiber couldbe suspended equably in the viscous chitosan solution. Chitin fiber/chitosan 3-Dcomposite rods with layer by layer structure were prepared by in-situ precipitation.Chitosan was continuous phase which could transfer stress, whereas chitin fibers asreinforcement element were randomly dispersed in chitosan matrix and could endureoutside stress so as to improve the mechanical properties of composite rods.The surface of filter paper fiber was accidented and the fiber reacted withchitosan to form small amount of Schiff-base, which could enhance the mechanicalcombining stress of the interface between fiber and matrix, so filter paper fiber couldreinforce chitosan rod effectively.Poly（4-aminophenylacetylene） macromolecular chains were thickly wrappedonto the outer surface of MWNTs byπ-πelectronic interaction and donor-acceptor（D-A） complexation, so water soluble MWNTs were uniformly dispersed in chitosanmatrix and could bear outside stress effectively. Alignment of MWNTs in chitosanmatrix has also been studied. MWNTs were coated byFe₃O₄/poly（4-aminophenylacetylene）, so they became water soluble and could beoriented by magnetic field. TEM results indicated that MWNTs were uniformlydispersed and parallel aligned in chitosan matrix.（2） Sodium aiginate and N-carboxyl propionyl chitosan sodium were used for reinforcing chitosan rods. FTIR spectra confirmed that amino groups and acetamidogroups on chitosan have stronger electrostatic attraction with carboxylate salt groups.So layer-by-layer structure of composite rods became much tighter compared withpure chitosan rod, and mechanical properties improved.（3） Sodium polyphosphate/chitosan composite rods with bionic hollow structureand layer structure have been constructed successfully. Bionic structure formingmechanism has been explored, the layer structure could be explained by LiesegangRing and the hollow structure could be controlled by precipitation time. FTIR spectraconfirmed that there are electrostatic attractions between sodium polyphosphate andchitosan. So the improved mechanical properties of composite rods could beattributed to strong electrostatic attraction, layer structure similar to wood’s annualring and hollow structure similar to bamboo.（4） Co60-γ-rays induces chitosan chain scission reaction, resulting in shortermolecular chains which are beneficial for segmental mobility due to lowerintermolecular attraction forces and less chain entanglement, so a higher level ofcrystallinity after irradiation could be observed. Enhanced crystallinity improves themechanical properties of rods, so Co60-γ-rays irradiation is an effective way toimprove the mechanical properties of 3-D biodegradable chitosan rods.Chitosan rods were self-crosslinked to form network structure throughcrosslinking reaction between amino groups caused by thermal effect of microwaveirradiation. The improvement of mechanical properties of chitosan rods treated bymicrowave could be attributed to thermal crosslinking reaction.（5） Chitosan rods and hydroxyapatite/chitosan nanocomposite rods werereinforced through covalently crosslinking to form network structure byglutaraldehyde. The size of hydroxyapatite particles became smaller after crosslinkingof chitosan matrix. Layer-by-layer structure became much tighter after crosslinkingand cracks in one layer turnned around when they reached another layer to absorbenergy, so the mechanical properties of 3-D chitosan rods enhanced.Mechanical properties of chitosan rods have been improved remarkably in thisresearch. Bending strength of bionic hollow sodium polyphosphate/chitosan composite rods, microwave treated rods and glutaraldehyde crosslinked rods arrivedat～180 MPa, which were approximately twice stronger than pure chitosan rods.Reinforced chitosan rods should be a novel internal fixation device for bone fracture.更多还原