Abstract：
Bundles of engineered collagen microfibers are promising synthetic tendons as substitutes for autogenous grafts. The purpose of this study was to develop high-speed and continuous spinning of collagen microfibers that involves stretching of collagen stream. Our study revealed the \'critical fibrillogenesis concentration (CFC)\' of neutralized collagen solutions, which is defined as the upper limit of the collagen concentration at which neutralized collagen molecules remain stable as long as they are cooled (⩽10 °C). Neutralized collagen solutions at collagen concentrations slightly below the CFC formed cord-like collagen gels comprising longitudinally aligned fibrils when extruded from nozzles into an ethanol bath. Dry collagen microfibers with a controlled diameter ranging from 122 ± 2-31.2 ± 1.7 μm can be spun from the cord-like gels using nozzles of various sizes. The spinning process was improved by including stretching of collagen stream to further reduce diameter and increase linear velocity. We extruded a collagen solution through a 182 μm diameter nozzle while simultaneously stretching it in an ethanol bath during gelation and fiber formation. This process resembles the stretching of a melted thermoplastic resin because it solidifies during melt spinning. The mechanical properties of the stretched collagen microfibers were comparable to the highest literature values obtained using microfluidic wet spinning, as they exhibited longitudinally aligned fibrils both on their surface and in their core. Previous wet spinning methods were unable to generate collagen microfibers with a consistent tendon-like fibrillar arrangement throughout the samples. Although the tangent modulus (137 ± 7 MPa) and stress at break of the swollen bundles of stretched microfibers (13.8 ± 1.9 MPa) were lower than those of human anterior cruciate ligament, they were within the same order of magnitude. We developed a spinning technique that produces narrow collagen microfibers with a tendon-like arrangement that can serve as artificial fiber units for collagen-based synthetic tendons.
摘要：
成束的工程胶原微纤维是有前途的合成肌腱，可替代自体移植物。这项研究的目的是开发涉及胶原蛋白流拉伸的胶原蛋白微纤维的高速连续纺丝。我们的研究揭示了中和胶原蛋白溶液的“临界原纤维形成浓度（CFC）”，定义为只要中和的胶原分子被冷却(≤10℃)就保持稳定的胶原浓度的上限。胶原浓度略低于CFC的中和胶原溶液在从喷嘴挤出到乙醇浴中时形成包含纵向排列的原纤维的索状胶原凝胶。可以使用各种尺寸的喷嘴从绳状凝胶纺出直径在122±2至31.2±1.7μm范围内受控的干燥胶原微纤维。通过包括胶原流的拉伸以进一步减小直径和增加线速度来改进纺丝过程。我们通过182μm直径的喷嘴挤出胶原蛋白溶液，同时在凝胶化和纤维形成过程中在乙醇浴中拉伸胶原蛋白溶液。该方法类似于熔融热塑性树脂的拉伸,因为它在熔融纺丝期间固化。拉伸胶原微纤维的机械性能与使用微流体湿法纺丝获得的最高文献值相当，因为它们在其表面和核心上都表现出纵向排列的原纤维。先前的湿纺方法不能在整个样品中产生具有一致的腱状原纤维排列的胶原微纤维。尽管拉伸微纤维的溶胀束的切线模量（101±16MPa）和断裂应力（10.5±0.5MPa）低于ACL，它们在同一数量级内。我们开发了一种纺丝技术，该技术可生产具有肌腱状排列的窄胶原蛋白微纤维，可用作基于胶原蛋白的合成肌腱的人造纤维单元。
