Zhang Huijie L, Cameron Ruth E, Best Serena M
Department of Materials Science and Metallurgy, University of Cambridge, UK.
Department of Materials Science and Metallurgy, University of Cambridge, UK.
J Mech Behav Biomed Mater. 2025 Nov;171:107121. doi: 10.1016/j.jmbbm.2025.107121. Epub 2025 Jul 3.
Collagen-based soft tissues are often anisotropic in structure, and in regenerative medicine, it is important that scaffolds are designed to closely mimic their architecture and mechanical behaviour. Existing testing standards are not directly applicable to anisotropic structures in physiologically relevant conditions. The challenge is therefore to systematically quantify mechanical anisotropy, nonlinear tensile behaviour, and both in vitro degradation and fatigue in a way appropriate for soft, porous, natural macromolecular structures. In this study, we fabricated collagen scaffolds with elongated porosity via directional freeze-drying and then chemically crosslinked them using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). Compressive mechanical behaviour was monitored along two characteristic directions, and distinct stress-strain curves were observed. The elastic modulus was identified as 6.42 kPa and 1.02 kPa along the two directions. Nonlinear tensile behaviour was characterised using the tangent modulus, which varied from 25 kPa to 270 kPa before failure. Standardised methods for monitoring degradation at 37 °C were developed. In vitro degradation was investigated by immersing scaffolds in deionised water for 60 days, during which the critical stress decreased by 30% in the first 30 days. Fatigue was studied by monitoring the stress-strain curves under 20% tensile strain for 1000 cycles. Scaffolds exhibited weaker mechanical integrity when loaded at 1.43 Hz. This study addresses the lack of standardised testing methods for anisotropic ice-templated collagen scaffolds by establishing a set of protocols to characterise the mechanical anisotropy, quantify tensile behaviour, and monitor scaffold degradation. This flexible characterisation toolkit can be adapted to specific sample treatments during tissue culture.
基于胶原蛋白的软组织在结构上通常是各向异性的，在再生医学中，设计出能紧密模拟其结构和力学行为的支架非常重要。现有的测试标准并不直接适用于生理相关条件下的各向异性结构。因此，挑战在于以一种适用于柔软、多孔的天然大分子结构的方式，系统地量化力学各向异性、非线性拉伸行为以及体外降解和疲劳性能。在本研究中，我们通过定向冷冻干燥制备了具有细长孔隙率的胶原蛋白支架，然后使用1-乙基-3-(3-二甲基氨基丙基)碳二亚胺盐酸盐（EDC）和N-羟基琥珀酰亚胺（NHS）对其进行化学交联。沿着两个特征方向监测压缩力学行为，观察到了不同的应力-应变曲线。在这两个方向上，弹性模量分别确定为6.42 kPa和1.02 kPa。使用切线模量来表征非线性拉伸行为，其在失效前从25 kPa变化到270 kPa。开发了在37°C下监测降解的标准化方法。通过将支架浸泡在去离子水中60天来研究体外降解，在此期间，临界应力在前30天内下降了30%。通过监测在20%拉伸应变下1000个循环的应力-应变曲线来研究疲劳。当以1.43 Hz加载时，支架表现出较弱的机械完整性。本研究通过建立一套表征力学各向异性、量化拉伸行为和监测支架降解的方案，解决了各向异性冰模板化胶原蛋白支架缺乏标准化测试方法的问题。这个灵活的表征工具包可以在组织培养过程中适应特定的样品处理。
