Cambridge Centre for Medical Materials, Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Rd, Cambridge, CB3 0FS, UK.
J Mater Sci Mater Med. 2020 May 4;31(5):46. doi: 10.1007/s10856-020-06381-x.
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.
在组织构建的发育过程中，由于没有血管来帮助运输，因此培养在三维支架中的细胞的营养物质扩散对于细胞存活至关重要。人们已经做出了巨大的努力来描述结构对纳米多孔水凝胶中溶质扩散率的影响，但对于微孔支架尚未尝试进行类似的全面描述。在这里，我们利用具有在 150-250μm 范围内的孔径和各向同性或取向形态的冻干胶原支架来研究荧光葡聚糖分子的扩散率。光漂白后的荧光恢复用于测量单个孔内溶质的自扩散率，而通过随时间评估材料内溶质浓度分布来研究大于孔径的标度上的菲克扩散。我们表明，不仅支架的形态参数会显著影响溶质的扩散率，而且对这种扩散率的评估取决于所研究分子的扩散尺度，结果导致扩散系数受支架结构的不同影响。所提供的结果可以指导具有定制扩散率和营养物浓度分布的支架的设计。
