Department of Biomedical Engineering, Ohio State University, Columbus, OH, 43210, USA.
J Mater Sci Mater Med. 2014 Feb;25(2):297-309. doi: 10.1007/s10856-013-5077-0. Epub 2013 Nov 1.
Tissue engineering scaffold degradation in aqueous environments is a widely recognized factor determining the fate of the associated anchorage-dependent cells. Electrospun blends of synthetic polycaprolactone (PCL) and a biological polymer, gelatin, of 25, 50, and 75 wt% were investigated for alterations in crystallinity, microstructure and morphology following widely used in vitro biological exposures. To our knowledge, the effects of these different aqueous-based biological media compositions on the degradation of these blends have never been directly compared. X-ray diffraction (XRD) analysis exposed that differences in PCL crystallinity were observed following exposures to phosphate buffered solution (PBS), Dulbecco's modified eagle medium (DMEM) cell culture media, and DI water following 7 days of exposure at 37 °C. XRD data suggested that in vitro medium exposures aid in providing chain mobility and rearrangement due to hydrolytic degradation of the gelatin phase, allowing previously constrained, poorly crystalline PCL regions to achieve more intense reflections resulting in the presence of crystalline peaks. The dry, as-spun modulus of relatively soft 100 % PCL fibers was approximately 10 % of any gelatin-containing composition. Tensile testing results indicate that hydrated gelatin containing scaffolds on average had a fivefold increase in elongation compared to as-spun scaffolds. After 24-h of aqueous exposure, the elastic modulus decreased in proportion to increasing gelatin content. After 1 day of exposure, the 75 and 100 % gelatin compositions largely ceased to display measurable values of modulus, elongation or tensile strength due to considerable hydrolytic degradation. On a relative basis, common aqueous in vitro medium exposures (deionized water, PBS, and DMEM) resulted in significantly divergent amounts of crystalline PCL, overall microstructure and fiber morphology in the blended compositions, subsequently 'shielding' scaffolds from significant changes in mechanical properties after 24-h of exposure. Understanding electrospun PCL-gelatin scaffold dynamics in different aqueous-based cell culture medias enables the ability to tailor scaffold composition to 'tune' degradation rate, microstructure, and long-term mechanical stability for optimal cellular growth, proliferation, and maturation.
在水介质环境中，组织工程支架的降解是决定相关锚定依赖性细胞命运的一个广泛公认的因素。我们研究了聚己内酯（PCL）与生物聚合物明胶的 25、50 和 75wt%的共混物在广泛使用的体外生物暴露后的结晶度、微观结构和形态的变化。据我们所知，这些不同的基于水的生物介质成分对这些共混物降解的影响从未被直接比较过。X 射线衍射（XRD）分析表明，在暴露于磷酸盐缓冲溶液（PBS）、DMEM 细胞培养基和 DI 水 7 天后，暴露于 37°C 下，PCL 的结晶度存在差异。XRD 数据表明，体外介质暴露有助于通过明胶相的水解降解提供链流动性和重排，使先前受约束的、结晶较差的 PCL 区域能够获得更强的反射，从而产生结晶峰。相对较软的 100%PCL 纤维的干燥、未拉伸模量约为任何含明胶组合物的 10%。拉伸测试结果表明，与未拉伸支架相比，含水化明胶的支架的伸长率平均增加了五倍。在水暴露 24 小时后，弹性模量与明胶含量成比例降低。暴露 1 天后，由于水解降解相当大，75%和 100%明胶组成物在很大程度上不再显示模量、伸长率或拉伸强度的可测量值。相对而言，常见的体外水性介质暴露（去离子水、PBS 和 DMEM）导致共混物中结晶 PCL、整体微观结构和纤维形态发生显著差异，随后在 24 小时暴露后使支架的机械性能变化“屏蔽”。了解不同水性细胞培养基中电纺 PCL-明胶支架的动力学特性，可以使支架的组成能够“调整”降解速率、微观结构和长期机械稳定性，以实现最佳细胞生长、增殖和成熟。
