Diffusion of nutrients to cells cultured within three-dimensional scaffolds is fundamental for cell survival during development of the tissue construct, when no vasculature is present to aid transport. Significant efforts have been made to characterize the effect of structure on solute diffusivity in nanoporous hydrogels, yet a similar thorough characterization has not been attempted for microporous scaffolds. Here, we make use of freeze-dried collagen scaffolds, possessing pore sizes in the range 150-250 μm and isotropic or aligned morphology, to study the diffusivity of fluorescent dextran molecules. Fluorescence recovery after photobleaching is used to measure the self diffusivity of the solutes within single pores, while Fickian diffusion over scales larger than the pore size is studied by assessing the solute concentration profile within the materials over time. We show that, not only do the morphological parameters of the scaffolds significantly affect the diffusivity of the solutes, but also that the assessment of such diffusivity depends on the length scale of diffusion of the molecules under investigation, with the resulting diffusion coefficients being differently affected by the scaffold structure. The results provided can guide the design of scaffolds with tailored diffusivity and nutrient concentration profiles.

中文翻译：

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微孔组织工程支架内的尺度和结构依赖的溶质扩散率。

当没有脉管系统帮助运输时，营养物质扩散到三维支架内培养的细胞是组织构建体发育过程中细胞存活的基础。人们已经做出了巨大的努力来表征结构对纳米多孔水凝胶中溶质扩散性的影响，但尚未尝试对微孔支架进行类似的彻底表征。在这里，我们利用孔径在 150-250 μm 范围内且具有各向同性或排列形态的冻干胶原蛋白支架来研究荧光右旋糖酐分子的扩散性。光漂白后的荧光恢复用于测量单个孔内溶质的自扩散率，而通过评估材料内溶质浓度随时间的变化来研究大于孔径的尺度上的菲克扩散。我们表明，不仅支架的形态参数显着影响溶质的扩散率，而且这种扩散率的评估取决于所研究分子的扩散长度尺度，由此产生的扩散系数受到不同的影响通过脚手架结构。提供的结果可以指导具有定制扩散率和营养浓度分布的支架设计。