Abstract：
Tissue engineered scaffolds are needed to support physiological loads and emulate the micrometer-scale strain gradients within tissues that guide cell mechanobiological responses. We designed and fabricated micro-truss structures to possess spatially varying geometry and controlled stiffness gradients. Using a custom projection microstereolithography (μSLA) system, using digital light projection (DLP), and photopolymerizable poly(ethylene glycol) diacrylate (PEGDA) hydrogel monomers, three designs with feature sizes < 200 μm were formed: (1) uniform structure with 1 MPa structural modulus ( E ) designed to match equilibrium modulus of healthy articular cartilage, (2) E = 1 MPa gradient structure designed to vary strain with depth, and (3) osteochondral bilayer with distinct cartilage ( E = 1 MPa) and bone ( E = 7 MPa) layers. Finite element models (FEM) guided design and predicted the local mechanical environment. Empty trusses and poly(ethylene glycol) norbornene hydrogel-infilled composite trusses were compressed during X-ray microscopy (XRM) imaging to evaluate regional stiffnesses. Our designs achieved target moduli for cartilage and bone while maintaining 68-81% porosity. Combined XRM imaging and compression of empty and hydrogel-infilled micro-truss structures revealed regional stiffnesses that were accurately predicted by FEM. In the infilling hydrogel, FEM demonstrated the stress-shielding effect of reinforcing structures while predicting strain distributions. Composite scaffolds made from stiff μSLA-printed polymers support physiological load levels and enable controlled mechanical property gradients which may improve in vivo outcomes for osteochondral defect tissue regeneration. Advanced 3D imaging and FE analysis provide insights into the local mechanical environment surrounding cells in composite scaffolds.
摘要：
需要组织工程支架来支持生理负荷并模拟组织内引导细胞机械生物学反应的微米级应变梯度。我们设计和制造的微桁架结构具有空间变化的几何形状和受控的刚度梯度。使用自定义投影微立体光刻(μSLA)系统，使用数字光投影（DLP），和可光聚合的聚(乙二醇)二丙烯酸酯(PEGDA)水凝胶单体，形成特征尺寸<200μm的三种设计：（1）具有1MPa结构模量的均匀结构（E）设计为匹配健康关节软骨的平衡模量，（2）E=1MPa梯度结构，设计用于随深度变化应变，和(3)具有不同软骨层(E=1MPa)和骨层(E=7MPa)的骨软骨双层。有限元模型（FEM）指导设计并预测局部机械环境。在X射线显微镜（XRM）成像过程中压缩空桁架和聚（乙二醇）降冰片烯水凝胶填充的复合桁架，以评估区域刚度。我们的设计实现了软骨和骨骼的目标模量，同时保持了68-81％的孔隙率。空的和水凝胶填充的微桁架结构的组合XRM成像和压缩显示了FEM准确预测的区域刚度。在填充水凝胶中，FEM在预测应变分布的同时证明了加固结构的应力屏蔽效应。由刚性μSLA打印的聚合物制成的复合支架支持生理负荷水平，并能够控制机械性能梯度，这可以改善骨软骨缺损组织再生的体内结果。先进的3D成像和FE分析提供了对复合支架中细胞周围的局部机械环境的见解。
