聚乳酸/羟基磷灰石原位复合纤维热压成型及性能研究
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摘要
针对HA/PDLLA共混电纺纤维中HA载入量不大、易发生团聚等,采用原位沉积法构建复合纤维。复合纤维膜中存在于纤维表面的非化学计量的HA,使其具有优良的再矿化性能,同时在降解过程可保护纤维的形态完整。PDLLA上C=O的伸缩振动峰和HA中OH-的伸缩振动峰发生蓝移,复合纤维的玻璃化转变温度随HA载入量增加而上升,证明原位沉积HA/PDLLA复合纤维膜中PDLLA与原位生成的HA存在氢键相互作用。复合纤维膜的力学性能显著提高,HA载入量25.2wt%的原位复合纤维膜的拉伸强度为8.2±1.1 MPa,杨氏模量为63.5±5.6 MPa。细胞与支架结合良好,显著促进了细胞的增殖和分化,有望作为医疗装置的涂层材料和组织工程支架。
为解决杂乱排列纤维力学性能低和力学各向同性问题,通过高速旋转滚筒收集定向纤维,取向度为75.4±3.6%；采用原位沉积法制备定向复合纤维,使得纤维取向后力学强度分布上主要沿轴向进行分布,当HA载入量为25.2wt%,拉伸强度为17.2±3.1 MPa。通过正交设计优化热压工艺,热压成型后不改变纤维结构的完整性,纤维收缩性小,且纤维之间形成触点式粘结结构；定向排列原位复合纤维的热压材料力学强度显著增强,且沿纤维轴向和径向呈现显著差异,当HA载入量25.2wt%,沿纤维轴向和径向的强度分别为36.2±2.2和5.5±0.2 MPa。通过空间仿生构造,将定向排列纤维进行不同角度叠合后,再优化热压成型,制备具有空间力学分布各向异性的复合制件,拟合得到单轴拉伸强度与纤维排列层间夹角的定量关系。与定向PDLLA纤维热压材料相比,定向排列原位复合纤维的热压材料具有更好的力学性能和较快的降解速率,同时由于表面亲水性增加,可促进细胞的铺展生长和增殖分化,有望作为骨修复内固定材料。
模拟骨修复内固定材料的微动环境,采用切向微动磨损试验,初步研究复合材料的摩擦学性能。定向纤维热压材料主要表现为纤维径向方向上磨粒和磨屑的堆积和少量的裂纹生成,纤维轴向方向上为粒子的自我修复和润滑。定向排列原位复合纤维轴向具有优良的摩擦磨损性能,进入稳态磨损后,摩擦系数仅为0.22,耐磨性好,有望应用在骨组织修复领域。
Development of fibrous nanocomposites of hydroxyapatite (HA) and poly(DL-lactide) (PDLLA) offers great potential as tissue engineering scaffolds. Fibrous HA/PDLLA composites formed from in situ growth of HA within electrospun fibers were investigated with respect to the mechanical performances, biomineralization capability, degradation behaviors, cell growth and differentiation profiles. The tensile strength and Young's moduli of in situ grown composites (IGC) were 8.2 and 63.5 MPa, respectively, which were significantly higher than those of blend electrospun composites (BEC) with 25.2% of HA inoculation (p<0.05). It was due to the presence and uniform distribution of nano-HA on the fiber surface and interfacial interactions between HA and the matrix polymer. The interactions were approved by the blue-shifts of C=O stretching and OH- stretching modes and the increases in glass transition temperatures of fibrous composites. The localization of apatite phase on the fiber surface improved the biomineralization capability and enhanced the morphological stability of the fibers and fibrous mats even when the degradation of matrix polymer was detected. The results of cell culture indicated that the cell viability and activity levels of alkaline phosphatase on composites IGC were significantly higher than those of composites BEC (p<0.05). In situ grown fibrous composites acted as an excellent cell support to maintain desirable cell-substrate interactions, to provide favorable conditions for cell proliferation and to stimulate the osteogenic differentiation.
Low mechanical properties and their homogeneous distribution were indicated for randomly arranged fibers, and aligned fibers were collected on high-speed rotating mandrel. Aligned fibrous mats of IGC were obtained with the oritentation degree of 75.4±3.6% and HA loading of 25.2wt%. The mechanical property was determined on the axial direction, and the tensile strength of 17.2±3.1MPa was indicated, which was significantly higher than that of randomly distributed fibers (p<0.05); Orthogonal table of L9(3)4 was employed to optimize the parameters of hot pressing, whose optimized temperature, pressure and duration were 60℃,2 MPa and 10 min, respectively. Point-bonded cross-linking structure was formed and minimal shrinkage of fibrous mats with the integrity of fiber structure was detected. Hot-pressed composites from aligned IGC fibrous mats indicated significanlt higher mechanical properties than those from randomly distributed IGC (p<0.05). The ultimal tessile strength was 36.2±2.2 and 5.5±0.2 MPa on the axial and radial directions, respectively. To mimetic the high-level structure of the extracellular matrix of hard tissues, aliged fibrous mats were construted layer-by-layer with the interlayer angles of 0°、30°、45°and 90°, and then processed by hot press. Composite materials with heterogeneous distribution of mechanical properties were obtained, and quantitative relations between the ultimal tessile strength and interlayer angles were drafted by combining micromechanics formulae with experiment values. The hydrophilicity enhanced by HA loading, which resulted in catalyzed the process of degradation and provided favorable conditions for cell proliferation and to stimulate the osteogenic differentiation.
For determining the fretting friction properties of hot-pressed fibrous composites applied in bone repairement environment, tangential fretting were employed to determined friction coefficient and wear rate in air environment. The optimized parameters of fretting were normal force of 20 N, moving distance of 80±2μm, test frequency of 2 Hz and test cycles of 5×103. Hot-pressed composites from aligned IGC fibrous mats indicated indicated fretting particles and cracks on the axial direction, while self-repair and lubrication effects were detected on the radical direction. The lubrication efficiency of 0.22 was detected in the stable freeting phase, which showed potentials as bone repair subsitututes.
为解决杂乱排列纤维力学性能低和力学各向同性问题,通过高速旋转滚筒收集定向纤维,取向度为75.4±3.6%；采用原位沉积法制备定向复合纤维,使得纤维取向后力学强度分布上主要沿轴向进行分布,当HA载入量为25.2wt%,拉伸强度为17.2±3.1 MPa。通过正交设计优化热压工艺,热压成型后不改变纤维结构的完整性,纤维收缩性小,且纤维之间形成触点式粘结结构；定向排列原位复合纤维的热压材料力学强度显著增强,且沿纤维轴向和径向呈现显著差异,当HA载入量25.2wt%,沿纤维轴向和径向的强度分别为36.2±2.2和5.5±0.2 MPa。通过空间仿生构造,将定向排列纤维进行不同角度叠合后,再优化热压成型,制备具有空间力学分布各向异性的复合制件,拟合得到单轴拉伸强度与纤维排列层间夹角的定量关系。与定向PDLLA纤维热压材料相比,定向排列原位复合纤维的热压材料具有更好的力学性能和较快的降解速率,同时由于表面亲水性增加,可促进细胞的铺展生长和增殖分化,有望作为骨修复内固定材料。
模拟骨修复内固定材料的微动环境,采用切向微动磨损试验,初步研究复合材料的摩擦学性能。定向纤维热压材料主要表现为纤维径向方向上磨粒和磨屑的堆积和少量的裂纹生成,纤维轴向方向上为粒子的自我修复和润滑。定向排列原位复合纤维轴向具有优良的摩擦磨损性能,进入稳态磨损后,摩擦系数仅为0.22,耐磨性好,有望应用在骨组织修复领域。
Development of fibrous nanocomposites of hydroxyapatite (HA) and poly(DL-lactide) (PDLLA) offers great potential as tissue engineering scaffolds. Fibrous HA/PDLLA composites formed from in situ growth of HA within electrospun fibers were investigated with respect to the mechanical performances, biomineralization capability, degradation behaviors, cell growth and differentiation profiles. The tensile strength and Young's moduli of in situ grown composites (IGC) were 8.2 and 63.5 MPa, respectively, which were significantly higher than those of blend electrospun composites (BEC) with 25.2% of HA inoculation (p<0.05). It was due to the presence and uniform distribution of nano-HA on the fiber surface and interfacial interactions between HA and the matrix polymer. The interactions were approved by the blue-shifts of C=O stretching and OH- stretching modes and the increases in glass transition temperatures of fibrous composites. The localization of apatite phase on the fiber surface improved the biomineralization capability and enhanced the morphological stability of the fibers and fibrous mats even when the degradation of matrix polymer was detected. The results of cell culture indicated that the cell viability and activity levels of alkaline phosphatase on composites IGC were significantly higher than those of composites BEC (p<0.05). In situ grown fibrous composites acted as an excellent cell support to maintain desirable cell-substrate interactions, to provide favorable conditions for cell proliferation and to stimulate the osteogenic differentiation.
Low mechanical properties and their homogeneous distribution were indicated for randomly arranged fibers, and aligned fibers were collected on high-speed rotating mandrel. Aligned fibrous mats of IGC were obtained with the oritentation degree of 75.4±3.6% and HA loading of 25.2wt%. The mechanical property was determined on the axial direction, and the tensile strength of 17.2±3.1MPa was indicated, which was significantly higher than that of randomly distributed fibers (p<0.05); Orthogonal table of L9(3)4 was employed to optimize the parameters of hot pressing, whose optimized temperature, pressure and duration were 60℃,2 MPa and 10 min, respectively. Point-bonded cross-linking structure was formed and minimal shrinkage of fibrous mats with the integrity of fiber structure was detected. Hot-pressed composites from aligned IGC fibrous mats indicated significanlt higher mechanical properties than those from randomly distributed IGC (p<0.05). The ultimal tessile strength was 36.2±2.2 and 5.5±0.2 MPa on the axial and radial directions, respectively. To mimetic the high-level structure of the extracellular matrix of hard tissues, aliged fibrous mats were construted layer-by-layer with the interlayer angles of 0°、30°、45°and 90°, and then processed by hot press. Composite materials with heterogeneous distribution of mechanical properties were obtained, and quantitative relations between the ultimal tessile strength and interlayer angles were drafted by combining micromechanics formulae with experiment values. The hydrophilicity enhanced by HA loading, which resulted in catalyzed the process of degradation and provided favorable conditions for cell proliferation and to stimulate the osteogenic differentiation.
For determining the fretting friction properties of hot-pressed fibrous composites applied in bone repairement environment, tangential fretting were employed to determined friction coefficient and wear rate in air environment. The optimized parameters of fretting were normal force of 20 N, moving distance of 80±2μm, test frequency of 2 Hz and test cycles of 5×103. Hot-pressed composites from aligned IGC fibrous mats indicated indicated fretting particles and cracks on the axial direction, while self-repair and lubrication effects were detected on the radical direction. The lubrication efficiency of 0.22 was detected in the stable freeting phase, which showed potentials as bone repair subsitututes.
引文
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