Dynamic shear-influenced collagen self-assembly.
Dynamic shear-influenced collagen self-assembly.
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DOI：
10.1016/j.biomaterials.2009.07.070
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发表时间：
2009-12
期刊：
影响因子：
14
通讯作者：
Ruberti, Jeffrey W.
中科院分区：
文献类型：
--
作者：
Saeidi, Nima;Sander, Edward A.;Ruberti, Jeffrey W.
影响自组装生物分子系统的聚合方向的能力具有产生具有极高各向异性的材料的潜力。在高度定向的细胞群产生对齐的且通常承重的组织的生物系统中，这种有组织的分子支架可以帮助细胞接触引导用于工程化组织构建体（例如角膜和肌腱）。在这项调查中，我们研究了详细的动力学胃蛋白酶提取的I型牛胶原蛋白组装在玻璃表面上的影响下，两个板之间的流动。使用焦平面稳定的微分干涉对比（DIC）成像（60 x-1.4 NA）来解析和跟踪4种不同剪切速率（500、80、20和9 s-1）下硼硅酸盐玻璃上胶原聚集体的生长。使用Quick Freeze Deep Etch电子显微镜检查胶原原纤维/聚集体的详细形态。观察到玻璃上的原纤维成核快速发生（约2分钟），随后原纤维继续生长。生长速率以复杂的方式依赖于流动，在9 s-1的剪切速率下发生轴向生长的最高速率（0.1微米/秒）。最低的生长速率发生在最高的剪切。在实验过程中观察到原纤维既有分支又有连接。在20和80 s-1的中间剪切速率下观察到原纤维的最佳排列。然而，调查发现，原纤定向生长是不稳定的。在高剪切速率下，原纤维通常会转向下游，形成我们所称的“钩”，这可能是单体与初始胶原层或“垫”相互作用和高剪切速率的组合结果。此外，原纤维形态的QFDE检查表明，组装的原纤维结构不具有天然的D-周期性。相反，原纤维包含通常对齐的单体的集合，这些单体自组装以形成原纤维样聚集体。总之，尽管恒定的剪切速率明显影响胶原纤维排列，但天然样D带原纤维的高度组织化的胶原阵列的形成仍然是一个挑战。剪切的调节结合表面能图案化以产生高度对齐的初始垫可以提供原纤维形态和对齐的显著改善。
The ability to influence the direction of polymerization of a self-assembling biomolecular system has the potential to generate materials with extremely high anisotropy. In biological systems where highly-oriented cellular populations give rise to aligned and often load-bearing tissue such organized molecular scaffolds could aid in the contact guidance of cells for engineered tissue constructs (e.g cornea and tendon). In this investigation we examine the detailed dynamics of pepsin-extracted type I bovine collagen assembly on a glass surface under the influence of flow between two plates. Differential Interference Contrast (DIC) imaging (60x-1.4NA) with focal plane stabilization was used to resolve and track the growth of collagen aggregates on borosilicate glass for 4 different shear rates (500, 80, 20, and 9 s-1). The detailed morphology of the collagen fibrils/aggregates was examined using Quick Freeze Deep Etch electron microscopy. Nucleation of fibrils on the glass was observed to occur rapidly (~2 min) followed by continued growth of the fibrils. The growth rates were dependent on flow in a complex manner with the highest rate of axial growth (0.1 microns/sec) occurring at a shear rate of 9 s-1. The lowest growth rate occurred at the highest shear. Fibrils were observed to both branch and join during the experiments. The best alignment of fibrils was observed at intermediate shear rates of 20 and 80s-1. However, the investigation revealed that fibril directional growth was not stable. At high shear rates, fibrils would often turn downstream forming what we term “hooks” which are likely the combined result of monomer interaction with the initial collagen layer or “mat” and the high shear rate. Further, QFDE examination of fibril morphology demonstrated that the assembled fibrillar structure did not possess native D-periodicity. Instead, fibrils comprised a collection of generally aligned, monomers which were self-assembled to form a fibril-like aggregate. In conclusion, though constant shear-rate clearly influences collagen fibrillar alignment, the formation of highly-organized collagenous arrays of native-like D-banded fibrils remains a challenge. Modulation of shear in combination with surface energy patterning to produce a highly-aligned initial mat may provide significant improvement of both the fibril morphology and alignment.
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4.6
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