FEM modeling of the reinforcement mechanism of Hydroxyapatite in PLLA scaffolds produced by supercritical drying, for Tissue Engineering applications
FEM modeling of the reinforcement mechanism of Hydroxyapatite in PLLA scaffolds produced by supercritical drying, for Tissue Engineering applications
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DOI：
10.1016/j.jmbbm.2015.07.021
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发表时间：
2015-11-01
影响因子：
3.9
通讯作者：
Reverchon, E.
中科院分区：
文献类型：
--
作者：
Baldino, L.;Naddeo, F.;Reverchon, E.
采用超临界CO2干燥的方法制备了聚l -乳酸（PLLA）凝胶，并将其装载微量果糖颗粒作为致孔剂。这些结构显示了由孔隙素浸出在固体材料中留下的空隙产生的微孔结构，同时它们保持了凝胶的纳米结构，由纳米丝网络组成。这些支架还装载了羟基磷灰石（HA）纳米颗粒，相对于聚合物，从10到50% w/w，以改善PLLA结构的机械性能。基于微观和力学方面的考虑，我们提出了一种参数化的聚乳酸- ha复合材料有限元模型，该模型将聚乳酸- ha复合材料的微孔结构描述为紧密排列的等球体，将其纳米级结构描述为各向同性弯曲纤维的空间框架。基于扫描电镜图像并考虑HA纳米颗粒在PLLA纳米纤维周围形成同心圆柱体的情况，模拟了HA对支架力学性能的影响。模型分析证实，这些支架的力学性能取决于纳米纤维网络的连接，弯曲是导致网络变形的主要因素。有限元模型还考虑了纳米纤维网络中某些区域形成的HA多层涂层及其厚度随HA百分比的增加而增加。在有限元模型中，当HA百分比大于30% w/w时，当HA纳米颗粒制备的纳米纤维的负载表面指数达到0.14时，杨氏模量趋于平稳。(C) 2015 Elsevier Ltd.版权所有。
Scaffolds have been produced by supercritical CO2 drying of Poly-L-Lactid Acid (PLLA) gels loaded with micrometric fructose particles used as porogens. These structures show a microporous architecture generated by the voids left in the solid material by porogen leaching, while they maintain the nanostructure of the gel, consisting of a network of nanofilaments. These scaffolds have also been loaded with Hydroxyapatite (HA) nanopartides, from 10 to 50% w/w with respect to the polymer, to improve the mechanical properties of the PLLA structure.Based on miscroscopic and mechanical considerations, we propose a parametric Finite Element Method (FEM) model of PLLA-HA composites that describes the microporous structure as a close-packing of equal spheres and the nanoscale structure as a space frame of isotropic curved fibers. The effect of HA on the mechanical properties of the scaffolds has been modeled on the basis of SEM images and by taking into consideration the formation of concentric cylinders of HA nanoparticles around PLLA nanofibers. Modeling analysis confirms that mechanical properties of these scaffolds depend on nanofibrous network connections and that bending is the major factor causing deformation of the network. The FEM model also takes into account the formation of HA multi-layer coating on some areas in the nanofiber network and its increase in thickness with HA percentage.The Young modulus tends to a plateau for HA percentages larger than 30% w/w and when the coverage of the nanofibers produced by HA nanoparticles reaches a loaded surface index of 0.14 in the FEM model. (C) 2015 Elsevier Ltd. All rights reserved.