取向性纳米片状HAp/PLA结构仿生复合材料的制备科学及性能研究

Human bone is a hard tissue mainly consisting of nano-hydroxyapatite (HAp) with defined alignment. Finding a synthetic pathway to artificial analogs of bone represents a fundamental milestone in the development of high-performance composite materials for biomedical applications. Based upon our previous work on successful preparation of lamellar HAp using template synthesis, herein we propose a new approach to make the artificial bone-like biocomposite that makes use of the advantages of intercalation technique in favor of physically controlled alignment of HAp nano-platelet in polylactic acid (PLA). This results in a biocomposite, which will reproduce not only the oriented arrangement of the HAps in natural bones, but also the strong interfacial interactions with matrix in conventional intercalated composites. To this end, the physical morphology of nano-platelet HAp will be tuned by adjusting the template synthesis process. In addition, low molecular PLA will be grafted on the surface of the nano-HAp to allow PLA intercalate into the layered HAp galleries. The melt intercalation technique that has become a main stream for the preparation of intercalated nanocomposites and shows many advantages over solution intercalation will be employed to fabricate the HAp/PLA biocomposites with highly oriented and well-dispersed HAp and strong HAp-PLA interactions. The effects of the morphology of the nano-platelet HAp and its grafting on the melt intercalation processes, HAp-PLA bonding, and HAp distribution and arrangement in the PLA matrix will be investigated. The special emphasis will be given to correlating the structural parameters (including dimension, orientation, and distribution) with the mechanical properties, biocompatibility, and biomedical functions (bone formation) of the HAp/PLA biocomposites. This work is expected to open a new way of designing and fabricating a new type of novel sophisticated composites with structural resemblance to natural bones.

人骨中的主要无机相为呈均匀且定向排列的纳米片状羟基磷灰石（HAp），而人工合成的HAp多为纳米颗粒，其在基体中的可控分布以及与基体的良好界面结合一直是HAp复合材料发展的瓶颈。本项目在模板法合成片层HAp的基础上，拟充分利用插层复合材料的优点（即均匀分散和强界面结合），率先将“插层”概念引入到HAp生物复合材料领域，提出取向性纳米片状HAp/聚乳酸（PLA）结构仿生复合材料的制备方案。本项目拟先对HAp的几何结构进行调控，同时在其表面接枝低聚乳酸，进而研究HAp几何形态与表面接枝对PLA熔体“类插层”过程、HAp-PLA界面结合及HAp在PLA基体中分散与取向的调控机制，并重点研究HAp/PLA复合材料结构学参数（HAp尺度与形态、取向、分散等）与其力学性能、生物相容性及生物学功能（骨修复）的关联规律，为设计和制备高性能结构仿生的新型生物复合材料提供新的科学依据。

人骨中的主要无机相为纳米片状羟基磷灰石（HAp），而人工合成的HAp多为纳米颗粒，其在基体中的可控分布以及与基体的良好界面结合一直是人工HAp复合材料追求的目标。在模板法合成片层HAp的基础上，本项目充分利用插层复合材料的优点（即均匀分散和强界面结合），率先将“插层”概念引入到HAp生物复合材料领域，提出取向性纳米片状HAp/聚乳酸（PLA）结构仿生复合材料的制备方案。本项目首先采用模板合成工艺参数法制备了层状HAp，并对其几何结构参数进行了调控。在此基础上，采用直接熔融插层法将层片状HAp剥离为纳米片状羟基磷灰石（np-HAp），随后采用易于批量化生产的挤出和注塑工艺制备了结构仿生np-HAp/PLA纳米复合材料。本项目还对HAp进行了表面改性，结果发现，表面改性显著提高了复合材料的力学性能、热稳定性、亲水性以及抗水解性。研究表明，与PLA相比，np-HAp/PLA复合材料的力学性能显著提高。更为重要的是，np-HAp的加入显著改善了细胞的黏附和增殖能力。这些良好的性能归因于np-HAp/PLA纳米复合材料中仿生纳米片状HAp具有较大的比表面积，可为细胞和Ca2+的吸附提供更多的活性位点。动物实验结果显示，复合材料植入大鼠颅骨缺损处4周后，大鼠存活良好，有新骨形成。综上所述，np-HAp/PLA纳米复合材料有望成为一种新型的承重型生物材料。本项目的意义体现在解决了纳米片状HAp在基体材料中均匀分散的问题以及实现了复合材料界面结合强度的调控，这些成果为设计和制备性能优异的新型生物医用纳米复合材料提供了理论和技术依据。不仅如此，本项目的研究结果还可为其它系列的纳米片状HAp复合材料的制备提供依据。