P3 - Fishbone: Bones without cells as blueprints for durable, cyclically loaded nanocomposites: how does anosteocytic fishbone cope with fatigue?

对于哺乳动物的骨，骨细胞感知应变并启动疲劳损伤的重塑和修复被广泛接受。但是，高级硬骨鱼的骨骼缺乏骨细胞。它们是如何承受数百万次装载循环的？这种坚韧和抗疲劳的材料提出了一个理想的角色模型bioinspired composites.In这个项目中，我们阐明了结构实体上的长度尺度占主导地位的抗疲劳性anosteocytic鱼骨和它们如何相互作用，与细胞鱼骨比较。将通过组织学/材相学定量评估成分、纤维取向和孔隙率，重点是3D高分辨率调查。一个重点将是识别预先存在的微裂纹，纳米/微米尺度的孔隙度，和纳米尺寸的残余应力。基于全骨显微计算机断层扫描数据的有限元建模将帮助我们与基于数字图像相关性的应变数据协同作用，以更好地了解几何形状、宏观孔隙率、应力/应变分布和体内载荷条件之间的联系。我们将转移的结构特征确定为重要的耐疲劳性的有机-无机复合材料，同时修改其相对量，跨长度尺度和结合不同的加工路线。这将涉及理解复合材料加工对有机结构和有机/无机界面的影响。具有纳米级或微米级直径（以研究分级结构）和不同刚度的复合纤维将通过熔融电写入（MEW）、静电纺丝及其组合由天然或合成有机前体制成。MEW支架具有不同的宏观几何形状将产生与/不与羟基磷灰石（HA）纳米粒子，以提高疲劳性能，考虑到各向异性的影响，通过使用不同的晶体形状。将通过用具有/不具有并入的HA纳米颗粒的纳米纤维支撑这些宏观结构来获得夹层结构。所有的结构都将在其物理和化学性质方面进行研究。所有测试均在模拟体液中进行，考虑到保持时间和频率变化引起的粘弹性变形。与未加载状态一样，将在2D/3D中研究重力引起的结构变化。从具有中等矿化度的生物材料的角度来看，我们将通过提供关于组成如何影响抗疲劳性的知识以及如何以最少的伪影测试纳米复合材料来为FOR做出贡献。

For mammalian bone, it is widely accepted that osteocyte cells sense strains and initiate remodelling and repair of fatigue-damage. But bone of advanced teleost fish lacks osteocytes. How do they sustain millions of loading cycles? This tough and fatigue resistant material presents an ideal role model for bioinspired composites.In this project we elucidate which structural entities on which length scales dominate fatigue resistance of anosteocytic fishbone and how they interact, in comparison with cellular fishbone. Composition, fibre orientation and porosity will be evaluated quantitatively by histology/materialography, with an emphasis on 3D high resolution investigations. A focus will be on identfying pre-existing micro-cracks, nano-/ microscale porosity, and nm-sized residual stresses. Finite element modelling, based on whole bone microcomputed tomography data, will help us, in synergy with strain data based on digital image correlation to better understand connections between geometry, macro-porosity, stress/strain distributions and in vivo loading conditions. We will transfer structural features identified as important for the fatigue resistance to organic-inorganic composites, while modifying their relative amount, across length scales and by combining different processing routes. This will involve understanding the impact of composite processing on the organic structure and the organic/inorganic interfaces. Composite fibers with nano- or microscale diameters (to investigate hierarchical structures) and different stiffness will be made by melt electrowriting (MEW), electrospinning, and their combination from natural or synthetic organic precursors. MEW scaffolds with different macro-geometries will be produced with/without hydroxyapatite (HA) nanoparticles to enhance fatigue properties, considering effects of anisotropy by using different crystal shapes. Sandwich structures will be obtained by supporting these macrostructures with nanofibers with/without incorporated HA nanoparticles. All structures will be investigated in terms of their physical and chemical properties. All tests are performed in simulated body fluid, considering viscoelastic deformation by holding times and frequency variations. Fatigue-induced structural changes will be investigated in 2D/3D, as for the unloaded state. From the viewpoint of a biological material with intermediate mineralization degree, we will contribute to the FOR by providing knowledge on how composition affects fatigue resistance, and how the nanocomposites can be tested with minimum of artefacts.