剑麻纤维素纳米晶须/纳米羟基磷灰石协同增强改性聚乳酸复合生物材料及性能研究

Poly(L-lactic acid)-based (PLLA-based) composite material is an important biodegradable artificial bone replacement material,and one of hot topics in the field of biomedical materials. Due to the poorly interface compatiblity among the components of the PLLA-based composites and the mismatching of the degradation rate with the growth rate of bone tissue in the degradation process of the composite after implantation. In this project, sisal cellulose nano-whisker(SCNW) and nano-hydroxyapatite particles(nHAP) are used as raw materials based on their synergistic reinforce effect in PLLA composite materials. SCNW/PLLA biocomposites were prepared via in situ polymerization technology by grafting the oligomer on the SCNW and then forming the chemical bonds between SCNW and PLLA material surfaces. Furthermore, nHAP were deposited on the SCNW/PLLA biomaterial surface via in situ deposition method to achieve SCNW/PLLA/nHAP biocomposites. By optimizing the composition and fabricaton technological paramters, as well as investigating the effect of component content and structure and preparation technological conditions on the various performance of SCNW/PLLA/nHAP biocomposites. The fabrication technology is mastered, and he relation between preparation technology and microstructure as well as the properties of PLLA-based biocomposites is obtained. The interfacial interaction mechanism and synergistic reinforce mechanism are raised based on the research of interfacial compatibilities of between SCNW and PLLA as well as between nHAP and PLLA, and synergistic reinforce effect of SCNW/nHAP. Afterthat, the in vitro and in vivo degradation behavior of PLLA-based composites is studied, and the degradation mechanism in vitro and in vivo of PllA-based composites is advanced. Based on the investigation of the biocompatibility of SCNW/PLLA/nHAP composite biomaterials, the biological assessment system is established. The obtained results in this project will provide the experimental reference and theory evidence for the research of high-performance polymer-based biocomposites.

聚乳酸复合材料是一种重要的可降解可吸收人工骨替代材料，是生物医用材料领域的研究热点。针对聚乳酸复合材料存在界面相容性差及其在降解过程中降解速率与骨组织生长速率不匹配问题，本项目拟利用剑麻纤维素纳米晶须/纳米羟基磷灰石的协同增强效应，采用原位复合技术和原位沉积法制备剑麻纤维素纳米晶须/聚乳酸/纳米羟基磷灰石复合材料。通过优化复合材料的组成和工艺参数，研究复合材料组分含量、结构和工艺条件等对复合材料性能的影响，获得复合材料制备工艺及材料制备工艺-微结构-性能间的关系；研究增强相（纳米晶须、羟基磷灰石）与聚乳酸间的界面作用及增强相的协同增强效应，提出增强相与聚乳酸间的界面机理及增强相的协同增强机理；研究复合材料在体外模拟和体内降解过程中的行为，提出聚乳酸复合材料的降解机理；研究复合材料的生物相容性，建立聚乳酸复合生物材料的生物学评价体系；为高性能聚合物基生物材料研究提供实验参考和科学的理论依据。

本项目针对目前可降解聚乳酸材料存在界面相容性差及其在降解过程中降解速率与骨组织生长速率不匹配问题，将剑麻纤维素微晶与纳米羟基磷灰石掺入到聚乳酸材料中，利用剑麻纤维素微晶与羟基磷灰石的协调增强效应实现材料间的优势互补，通过调控剑麻纤维素微晶与羟基磷灰石的掺杂量，制备具有优异力学性能和生物学性能的聚乳酸基复合材料。项目实施四年来开展了以下方面的工作：（1）SCNW的制备及表征。采用剑麻纤维为原材料，通过碱、酸处理制备剑麻纤维素纳米晶须。所得剑麻纤维素中纤维素充分，具有良好的热稳定性。微晶的平均长度约为50μm、直径在5~10μm之间，纳米晶须的直径在5~60nm之间。（2）SCNW/PLLA生物材料的制备及性能研究。剑麻纤维素纳米晶须表面含有大量羟基，有很高的反应活性，利用接枝处理技术在SCNW表面接枝聚乳酸低聚物，采用原位复合技术制备SCNW/PLLA材料。SCNW的加入能够有效提高SCNW/PLLA材料的力学强度、断裂伸长率及材料的韧性。（3）SCNW/PLLA/nHAP复合生物材料的制备及性能研究。采用原位沉积法在SCNW/PLLA材料表面沉积纳米羟基磷灰石制备SCNW/PLLA/nHAP复合材料。SCNW/PLLA材料表面沉积层nHAP上的活性基团可与PLLA分子链之间发生作用，在两相界面处形成化学键合，提高两相界面的结合力和稳定性，SCNW/PLLA/nHAP复合材料的力学性能如强度、模量以及断裂伸长率等都可以通过控制nHAP粉末的加入量而得到合适力学性能的复合材料。（4）复合材料的降解性能研究。对聚乳酸复合生物材料分别以体外模式和体内模式进行降解性能研究。降解过程表明SCNW/PLLA/nHAP复合材料的吸水率比SCNW/PLLA材料和纯PLLA材料都要大，但是由于nHAP在PBS缓冲液中释放的碱性离子中和了PLLA降解过程中产生的酸性物质，减缓了高分子材料在酸性环境中的自催化加速降解作用，抑制了高分子材料的降解，从而延缓了SCNW/PLLA/nHAP复合材料的降解。（5）复合材料的生物学评价。采用细胞毒性试验、全身急性毒性试验、亚急性毒性试验、肌肉埋植等试验，对复合材料进行生物相容性研究。SCNW/PLLA/nHAP复合材料具有良好的生物相容性、血液相容性和体内组织相容性，有利于成骨细胞生长、分化及成骨活性表达，且不引起急性全身毒性反应和不产生毒性作用。