(178d) Engineering Hybrid Auxetic Scaffolds with Viscoelastic Hyaluronic Acid Hydrogels for Human Stem Cell Differentiation

To investigate the interaction between cells and the extracellular matrix, both two-dimensional (2D) and three-dimensional (3D) scaffolds/networks have been extensively employed in the field of bioengineering. The interaction between the extracellular matrix (ECM) and cells is governed by the inherent mechanical properties within the relationship of these two components. Typically, ECMs are fabricated using the same types of materials, which may vary in molecular weights, degree of crosslinking, and coating thickness. While a single-component microenvironment allows for a better understanding of the influence of a single variable on stem cell behaviors, it falls short in mimicking the complexity of the human body to accurately recapitulate the intricate conditions of the ECM. Therefore, the aim of this study is to create bicomponent biomaterials with a broad range of mechanical properties, such as stiffness, to enhance the resemblance of fibrous composite networks, imitating the actual cytoskeleton and extracellular matrix. Additionally, as auxetic materials advance, there is limited research on auxetic hydrogels with high water content. In this context, this study utilizes auxetic polyurethane (auPU) and hyaluronic acid (HA) (molecular weights: 100k, 200k, 1,000k) as fundamental components, displaying a significant difference in stiffness. Both components are modified with polydopamine (Cat). Subsequently, dopamine was introduced as a "bridge" to facilitate the binding of the two networks. Following the coating of auPU-Cat with HA-Cat hydrogel, the hybrid auxetic scaffold hydrogel was fabricated. Notably, the scaffolds coated with 1,000k HA-Cat exhibited the highest cover density and the lowest compression modulus, indicating elevated water content. In the subsequent steps, blood vessel organoids were differentiated and cultured on three distinct hybrid scaffolds, co-cultured with spinal cord organoids and pericytes to establish an in vitro blood-spinal cord barrier model. The higher molecular weight of HA-Cat promoted the generation of endothelial cells and the expression of tight junction markers. This study provides a platform for novel biomaterials that with rationally designed biophysical properties for organoid engineering, disease modeling, and drug discovery.