Collaborative Research: Biomimetic Bone: from Nano to Micro

ID: MPS/DMR/BMAT(7623) 1309657 PI: Gower， Laurie ORG：佛罗里达大学aid: MPS/DMR/BMAT(7623) 1309579 PI: Ruberti， Jeffrey ORG：东北大学标题：合作研究：仿生骨：从纳米到微技术部分：骨是一种分层结构的复合材料，在纳米尺度上由分散在自组装胶原原纤维间隙内的羟基磷灰石（HA）纳米晶体组成的互穿网络组成。本研究的目标是结合仿生加工技术，合成具有模拟骨的分层结构的胶原-羟基磷灰石复合材料，从而再现其力学性能。通过将其整合到下一个层次：骨的板层微观结构，所提出的工作扩展了先前在模拟骨的互穿纳米结构方面的成功。为了实现这一目标，将使用液晶前体胶原蛋白溶液生产高密度排列的高度组织化胶原蛋白，然后进行层压，以模拟在骨片中发现的扭曲胶合板结构。然后，微层状结构将通过PILP过程矿化，该过程已被证明会导致胶原蛋白的纤维内矿化，羟基磷灰石定向纳米晶体嵌入整个胶原原纤维的间隙。与骨骼匹配的成分，含有60-70 wt%的矿物质，可以通过PILP工艺实现；然而，即使有如此高的矿化程度，重建胶原海绵的固有孔隙率也会阻止复合材料支撑高负荷。因此，在骨骼中发现的高度组织化的胶原蛋白是重建骨骼特性所必需的。如果密集堆积的胶原蛋白阵列可以通过PILP工艺矿化，它应该是可能的，这是第一次，匹配骨的模量，强度和韧性。将对采用不同层压策略生成的多层复合材料进行微观力学测试，以评估所产生的结构的质量，以及各种结构参数（如层压厚度、纤维直径/组织、矿化程度等）如何与机械性能相关。最后，由于骨是一种机械结构，因此将对加载和卸载的胶原蛋白阵列进行PILP过程，以确定负载是否可能在骨形态发生中发挥关键作用。非技术部分：骨是一种非凡的复合材料，其基础结构设计可能有助于指导未来复合材料的设计。关于骨的力学性能已经有很多研究，但由于其分层结构，很难分离出各个结构层次下的各种强化和增韧机制的影响。通过开发一种体外模型系统，可以模拟不同水平的骨结构，这些特性可以在没有这种最重要的并发症的情况下进行检查，并受益于定制复合材料的单个组件的能力。这项工作也具有重要的生物医学意义，无论是在理解骨形成和特性的基础科学水平上，还是在开发下一代骨科生物材料的应用方面。这种仿生方法有可能导致通过自然骨重塑过程中发生的细胞过程重塑的承重生物可吸收骨替代品。关于教育，骨，由于其层次结构，提供了一个有趣的论坛，培训学生在材料科学领域的复合材料。教师研究经验（RET）和仿生材料推广计划（BMOP）等推广项目将继续进行，其中包括对研究生、本科生和K-12年级学生的培训和推广。此外，还提出了一项新的推广计划，将为附近城市的水族爱好者提供公开讲座，向他们展示他们喜欢的无脊椎生物矿物（如海胆和软体动物贝壳）背后有趣的材料科学，以及这些生物矿物与脊椎动物生物矿物之间的异同，以展示仿生工程师如何开发新型分层结构复合材料。

ID: MPS/DMR/BMAT(7623) 1309657 PI: Gower, Laurie ORG: University of FloridaID: MPS/DMR/BMAT(7623) 1309579 PI: Ruberti, Jeffrey ORG: Northeastern UniversityTitle: Collaborative Research: Biomimetic Bone: from Nano to MicroTechnical Part: Bone is a hierarchically-structured composite material which at the nanoscale comprises an interpenetrating network of hydroxyapatite (HA) nanocrystals dispersed within the interstices of self-assembled collagen fibrils. The goal of the proposed research is to use a combination of biomimetic processing techniques to synthesize collagen-hydroxyapatite composites with a hierarchical structure emulating bone, and thus reproduce its mechanical properties. The proposed work extends prior success in mimicking the interpenetrating nanostructure of bone, by integrating it to the next level of hierarchy: the lamellar microstructure of bone. To accomplish this goal, densely-packed arrays of highly organized collagen will be produced using liquid-crystalline precursor collagen solutions and then laminated to mimic the twisted plywood structure found in the lamellae of osteonal bone. The microlaminated structures will then be mineralized by the PILP process, which has been shown to lead to intrafibrillar mineralization of collagen, with oriented nanocrystals of hydroxyapatite embedded throughout the interstices of the collagen fibrils. Compositions matching bone, with 60-70 wt% mineral, can be achieved with the PILP process; however, even with this high degree of mineralization, the inherent porosity of reconstituted collagen sponges prevents the composites from supporting high loads. Thus, a highly-organized collagen, as is found in bone, is needed for reproducing the properties of bone. If the densely-packed collagen arrays can be mineralized via the PILP process, it should be possible, for the first time, to match the modulus, strength and toughness of bone. Micromechanical testing will be performed on the multilevel composites generated with different lamination strategies to assess the quality of the structures that are produced, and how the various structural parameters (such as lamellar thickness, fiber diameter/organization, degree of mineralization, etc.) correlate to mechanical properties. Finally, because bone is a mechanical structure, the PILP process will be conducted on both loaded and unloaded collagen arrays to determine if load might play a key role in bone morphogenesis.Non-Technical Part: Bone is a remarkable composite from which its underlying structural design may help guide the design of future composite materials. There have been many studies on the mechanical properties of bone, but because of its hierarchical structure, it is difficult to isolate the effects of various strengthening and toughening mechanisms that underlie each level of structure. By developing an in vitro model system that can mimic separate levels of bone structure, such properties might be examined without this overriding complication, and benefit from the ability to tailor individual components of the composites. This work also has important biomedical implications, both at the fundamental science level with respect to understanding bone formation and properties, and the applications side of developing the next generation of orthopedic biomaterials. This biomimetic approach has the potential to lead to load-bearing bioresorbable bone substitutes which are remodeled through the cellular processes that occur during natural bone remodeling. With respect to education, bone, due to its hierarchical structure, provides an interesting forum for training students about composites in the materials science field. Outreach programs such as Research Experience for Teachers (RET) and Biomimetic-Materials Outreach Program (BMOP) will be continued, which have included training and outreach to students at the graduate, undergraduate, and K-12 levels. A new outreach program is also proposed, in which public lectures will be provided to aquarists in nearby cities to show them the interesting materials science behind the invertebrate biominerals they enjoy as a hobby (such as sea urchins and mollusk shells), and the similarities/differences between these biominerals and vertebrate biominerals, to show how biomimetic engineers are developing novel hierarchically-structured composite materials.