聚磷酸钙纤维/纳米羟基磷灰石/聚乳酸复合材料的降解行为

Degradation of nano-hydroxyapatite/calcium polyphosphate fiber/polylactide composite

背景：可降解吸收性聚乳酸类骨内固定材料初始力学性能较低,易导致体内产生炎症反应,并且降解时间太长,限制了其在临床上的应用。目的：测定聚磷酸钙纤维/纳米羟基磷灰石/聚乳酸复合材料的力学性能和体外降解性能。设计、时间及地点：重复测量设计,于2006-08/2007-05在兰州交通大学材料工程研究所完成。材料：基体材料采用荷兰普拉克生化公司生产的聚乳酸（Mr300000）和聚消旋乳酸（Mr600000）的共混物（混合比例66/100）。增强材料为直径10~20μm、完全降解时间3个月以上的聚磷酸钙纤维（纤维与基体的比例为1/1）以及用水热法合成的纳米羟基磷灰石粒子。方法：采用复合材料共混工艺制备聚磷酸钙纤维/纳米羟基磷灰石/聚乳酸复合材料薄膜,然后真空热压成型,得到不同质量分数纳米羟基磷灰石（0,0.024,0.048,0.070）的聚磷酸钙纤维/纳米羟基磷灰石/聚乳酸复合材料试样。主要观察指标：复合材料降解前后的弯曲强度、弯曲模量。结果：①加入不同质量分数的纳米羟基磷灰石对复合材料的弯曲强度和弯曲模量均有一定的增强作用,质量分数为0.048时作用最强。②纳米羟基磷灰石质量分数为0.048时聚磷酸钙纤维/纳米羟基磷灰石/聚乳酸复合材料的弯曲强度251MPa,弯曲模量19GPa。与骨的力学性能相比,复合材料的初始强度、刚度（未降解）均大于皮质骨的强度和刚度。③在模拟人体环境的降解介质中降解12周后,聚磷酸钙纤维/纳米羟基磷灰石/聚乳酸复合材料的弯曲强度及弯曲模量为123MPa和7.24GPa。结论：聚磷酸钙纤维/纳米羟基磷灰石/聚乳酸复合材料的力学性能和体外降解性能与人骨组织相近。

BACKGROUND： Degradable polylactic acid materials for intraosseous fixation may induce the inflammatory reaction in vivo due to their low initial mechanical property, moreover, the degradation costs too long, which all limit the clinical application of polylactic acid materials. OBJECTIVE： To investigate the mechanical properties and the in vitro degradation behavior of nano-hydroxyapatite （n-HA）/calcium polyphosphate fiber （CPP）/polylactide （PLA） composite. DESIGN, TIME AND SETTING： This study, a repeated measurement, was performed in the Institute of Material Engineering, Lanzhou Jiaotong University （Lanzhou, Gansu, China） from August 2006 to May 2007. MATERIALS： PLA （Mr 300 000） and poly-D,L-lactic acid （Mr 600 000）, products of Dutch PURAC Biochemistry Company, were mixed at a ratio of 66/100 and applied as basis materials. CPP fiber at a diameter of 10-20 la m was completely degraded over three months, consisting of fibers and base materials at an equal ratio, n-HA particles were synthesized using hydrothermal method. CPP fiber and n-HA particles were used as reinforced materials. METHODS： The composite of CPP/n-HA/PLA were fabricated by mixing method in vacuum via compression molding process to obtain the test specimens containing n-HA at different mass fractions （0, 0.024, 0.048, 0.070）. MAINOUTCOME MEASURES： The bending strength and bending modulus of the resulted composite were investigated before and after degradation. RESULTS： The addition of n-HA could increase the bending strength and bending modulus of the composite, which reached 251 MPa and 19 Gpa respectively when the added n-HA was at 0.048 mass fraction. By contrast, the initial strength and rigidity （non-degradation） of the composite were higher than those of cortical bone. The bending strength and bending modulus of the composite were 123 MPa and 7.24 GPa, respectively, after it was dipped in artificial degradation solution at 37℃ in vitro for 12 weeks. CONCLUSION： The CPP/n-HA/PLA composite shows the identical mechanical properties and in vitro degradation with the human bone.