Structural determinants of hydration, mechanics and fluid flow in freeze-dried collagen scaffolds
Structural determinants of hydration, mechanics and fluid flow in freeze-dried collagen scaffolds
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DOI：
10.1016/j.actbio.2016.05.024
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发表时间：
2016-09-01
影响因子：
9.7
通讯作者：
Oyen, M. L.
中科院分区：
文献类型：
--
作者：
Offeddu, G. S.;Ashworth, J. C.;Oyen, M. L.
冻干支架由于其物理和生物学特性的灵活性，为广泛的组织提供了再生模板。结构的控制对于调节这些性质以及因此调节支架功能是至关重要的。然而，将这些支架建模为开孔泡沫的常见方法并不能完全解释其结构的复杂性。在这里，开孔模型的有效性检查在一系列的物理特性，严格连接形态的水化和机械性能。胶原蛋白支架的相对密度的系统变化，其特征在于使用扫描电子显微镜，X射线显微计算机断层扫描和球形压痕分析的时间依赖性多孔弹性框架。在形态学上，所有支架都处于开孔和闭孔模型之间，随着相对密度的增加接近闭孔模型。虽然孔径保持不变，但运输途径直径减小。较大的胶原组分也产生较大的体积溶胀的水化，虽然在孔径的变化是恒定的，相对较小的6%。机械上，干燥和水合支架模量随相对密度呈二次方变化，如开孔材料所预期的那样。然而，发现孔壁闭合的增加决定了水合支架响应的时间依赖性，渗透性的降低产生越来越多的弹性而不是粘弹性行为。这些结果表明，表征偏离开孔模型是至关重要的支架生物物理特性的全面了解，并提供了其他冻干生物材料的结构研究的模板。
Freeze-dried scaffolds provide regeneration templates for a wide range of tissues, due to their flexibility in physical and biological properties. Control of structure is crucial for tuning such properties, and therefore scaffold functionality. However, the common approach of modeling these scaffolds as open-cell foams does not fully account for their structural complexity. Here, the validity of the open-cell model is examined across a range of physical characteristics, rigorously linking morphology to hydration and mechanical properties. Collagen scaffolds with systematic changes in relative density were characterized using Scanning Electron Microscopy, X-ray Micro-Computed Tomography and spherical indentation analyzed in a time-dependent poroelastic framework. Morphologically, all scaffolds were mid-way between the open- and closed-cell models, approaching the closed-cell model as relative density increased. Although pore size remained constant, transport pathway diameter decreased. Larger collagen fractions also produced greater volume swelling on hydration, although the change in pore diameter was constant, and relatively small at 6%. Mechanically, the dry and hydrated scaffold moduli varied quadratically with relative density, as expected of open-cell materials. However, the increasing pore wall closure was found to determine the time-dependent nature of the hydrated scaffold response, with a decrease in permeability producing increasingly elastic rather than viscoelastic behavior. These results demonstrate that characterizing the deviation from the open-cell model is vital to gain a full understanding of scaffold biophysical properties, and provide a template for structural studies of other freeze-dried biomaterials.