(258a) Designing Hydrogels with Responsive and Hierarchical Structures for Application As Well-Defined Synthetic Extracellular Matrices

The properties of the extracellular matrix (ECM) (e.g., multiscale structure, mechanics, binding sites) are essential for the function of connective tissues throughout the body, from the collagen-rich loose connective tissue within the lung to the aligned connective tissue of tendon. To study connective tissue healing processes in vitro as well as direct them in vivo, we have designed synthetic hydrogels that mimic key aspects of the collagen-rich ECM. These hydrogels are constructed by assembly of multifunctional collagen mimetic peptides (mfCMPs) designed with i) hydrogen bonding blocks for the formation of triple helices and control of their stability, ii) sticky ends for the formation of nano- and micro-fibrils, and iii) reactive handles, allyloxycarbonyl (alloc) and azide, for covalent crosslinking and labeling, respectively. We have established rapid, robust, and scalable workflows for synthesis of these mfCMPs to facilitate their use in the construction of hydrogels for both fundamental and translational applications. Specifically, these assembled structures were crosslinked by photopolymerization with multi-arm poly(ethylene glycol) (PEG) tetrathiol, a difunctional alloc cell-degradable peptide, and a monofunctional alloc integrin-binding peptide, allowing control of the structure, mechanical properties, and bioactivity of the resulting hydrogels. Human mesenchymal stem cells (hMSCs) encapsulated within these mfCMP hydrogels exhibit good viability (>85%) and significant elongation during three-dimensional culture, along with deposition of cell-secreted collagen I amongst other proteins, where the underlying fibrous hydrogel structure can be examined in three dimensions with high-resolution confocal microscopy. Further, in response to a chemokine gradient, these hMSCs exhibit directional migration and enhanced motility relative to more homogeneously-structured PEG-peptide hydrogels without mfCMPs. Our on-going work is investigating the use of these collagen mimetic materials for more fundamental studies to examine cell responses in fibrous wound-healing microenvironments, as well as for triggered property modulation, and for translational studies to implement these materials in tissues toward enhanced regeneration.