Approaches for the creation of soft materials, particularly hydrogels, with hierarchical structure are of interest in a variety of applications owing to their unique properties. In the context of tissue mimics, hydrogels with multiscale structures more accurately capture the complexities of tissues within the body (e.g., fibrous collagen-rich microenvironments). However, cytocompatible fabrication of such materials with hierarchical structures and independent control of mechanical and biochemical properties remains challenging and is needed for probing and directing cell-microenvironment interactions for three-dimensional (3D) cell encapsulation and culture applications. To address this, we have designed innovative multifunctional assembling peptides: these unique peptides contain a core block that mimics the structure of collagen for achieving relevant melting temperatures; 'sticky' ends to promote assembly of long fibrils; and a biocompatible reactive handle that is orthogonal to assembly to allow the formation of desired multiscale structures and their subsequent rapid, light-triggered integration within covalently crosslinked synthetic hydrogels. Nano- to micro-fibrils were observed to form in physiologically-relevant aqueous solutions, where both underlying peptide chemical structure and assembly conditions were observed to impact the resulting fibril sizes. These assembled structures were 'locked' into place and integrated as linkers within cell-degradable, bioactive hydrogels formed with photoinitiated thiol-ene 'click' chemistry. Hydrogel compositions were identified for achieving robust mechanical properties like those of soft tissues while also retaining higher ordered structures after photopolymerization. The utility of these innovative materials for 3D cell culture was demonstrated with human mesenchymal stem cells, where cell morphologies reminiscent of responses to assembled native collagen were observed now with a fully synthetic material. Using a bottom-up approach, a new materials platform has been established that combines the advantageous properties of covalent and assembling chemistries for the creation of synthetic hydrogels with controllable nanostructure, mechanical properties, and biochemical content.

中文翻译：

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利用多功能组装肽进行 3D 细胞培养的分层结构水凝胶。

具有分层结构的软材料（特别是水凝胶）的创建方法由于其独特的性质而在各种应用中受到关注。在组织模拟的背景下，具有多尺度结构的水凝胶可以更准确地捕捉体内组织的复杂性（例如富含纤维胶原的微环境）。然而，这种具有分层结构和独立控制机械和生化特性的材料的细胞相容性制造仍然具有挑战性，并且需要探测和指导三维（3D）细胞封装和培养应用的细胞-微环境相互作用。为了解决这个问题，我们设计了创新的多功能组装肽：这些独特的肽包含一个模仿胶原蛋白结构的核心块，以实现相关的熔化温度；“粘性”末端促进长原纤维的组装；以及与组装正交的生物相容性反应手柄，以允许形成所需的多尺度结构，并随后在共价交联的合成水凝胶中快速、光触发整合。观察到纳米至微米原纤维在生理相关的水溶液中形成，其中观察到潜在的肽化学结构和组装条件都会影响所得原纤维的尺寸。这些组装的结构被“锁定”到位，并作为连接体整合到由光引发硫醇烯“点击”化学形成的可细胞降解的生物活性水凝胶中。水凝胶组合物被认为可以实现像软组织一样强大的机械性能，同时在光聚合后保留更高的有序结构。这些创新材料在 3D 细胞培养中的实用性已通过人类间充质干细胞得到证实，其中细胞形态让人联想到对组装的天然胶原蛋白的反应，现在可以使用全合成材料观察到。采用自下而上的方法，建立了一个新材料平台，结合了共价化学和组装化学的有利特性，用于创建具有可控纳米结构、机械性能和生化含量的合成水凝胶。