该研究团队报道了一种由纤维素纳米晶体和明胶衍生的工程共价交联纳米纤维水凝胶。水凝胶组成的变化使其剪切模量发生了大范围的改变。水凝胶表现出剪切硬化和压缩引起的软化，与仿射模型的预测一致。不同成分的水凝胶的阈值非线性应力和应变具有普遍性，表明刚性细丝形成的网络具有普遍的非线性力学性能。实验结果与描述由刚性细丝形成的网络变形的仿射模型一致。这一研究结果有助于深入了解控制纤维网络非线性生物力学的结构特征，并为未来研究非线性力学特性在生物学中的应用提供了平台。
据悉，由生物聚合物如胶原蛋白或纤维蛋白形成的纤维网络表现出非线性力学行为。这些网络在弱剪切和拉伸应变下经历强硬化，但在压缩应变下软化，这与由分子形成的柔性链网络变形的响应显著不同。纤维网络的非线性特性是由于组成纤维的力学不对称，其中拉伸模量明显大于弯曲模量。通常，非线性力学行为的研究是在生物聚合物形成的水凝胶上进行的，但这种方法对网络架构的控制有限。
附：英文原文
Title: Nanocolloidal hydrogel mimics the structure and nonlinear mechanical properties of biological fibrous networks
Author: Prince, Elisabeth, Morozova, Sofia, Chen, Zhengkun, Adibnia, Vahid, Yakavets, Ilya, Panyukov, Sergey, Rubinstein, Michael, Kumacheva, Eugenia
Issue&Volume: 2023-12-13
Abstract: Fibrous networks formed by biological polymers such as collagen or fibrin exhibit nonlinear mechanical behavior. They undergo strong stiffening in response to weak shear and elongational strains, but soften under compressional strain, in striking difference with the response to the deformation of flexible-strand networks formed by molecules. The nonlinear properties of fibrous networks are attributed to the mechanical asymmetry of the constituent filaments, for which a stretching modulus is significantly larger than the bending modulus. Studies of the nonlinear mechanical behavior are generally performed on hydrogels formed by biological polymers, which offers limited control over network architecture. Here, we report an engineered covalently cross-linked nanofibrillar hydrogel derived from cellulose nanocrystals and gelatin. The variation in hydrogel composition provided a broad-range change in its shear modulus. The hydrogel exhibited both shear-stiffening and compression-induced softening, in agreement with the predictions of the affine model. The threshold nonlinear stress and strain were universal for the hydrogels with different compositions, which suggested that nonlinear mechanical properties are general for networks formed by rigid filaments. The experimental results were in agreement with an affine model describing deformation of the network formed by rigid filaments. Our results lend insight into the structural features that govern the nonlinear biomechanics of fibrous networks and provide a platform for future studies of the biological impact of nonlinear mechanical properties.
DOI: 10.1073/pnas.2220755120
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2220755120