Catalyst-Free Collagen Filament Crosslinking for Engineering Anisotropic and Mechanically Robust Tissue Scaffolds

Engineering mechanically resilient hydrogels from naturally derived proteins, such as collagen and gelatin, remains a key challenge in tissue regeneration, particularly when cell compatibility and structural integrity are simultaneously required. Here, a bioorthogonal crosslinking strategy using rhodamine and polyethylene glycol (PEG) is reported to fabricate dense, mechanically reinforced collagen hydrogels. PEG-mediated dehydration induces spontaneous peptide bond formation between rhodamine and collagen without the need for additional catalysts, yielding fibrous protein networks with enhanced stiffness. To enable anisotropic tissue engineering, this crosslinking method is integrated with wet-spinning to produce uniaxially aligned collagen filaments. These constructs exhibit high mechanical strength and support human adipose-derived stem cell (hASC) encapsulation. Mechanotransductive signaling, including cytoskeletal organization and myogenic gene expression, is effectively activated within the aligned filaments. The applicability of cell-laden filaments in a murine volumetric muscle loss model is demonstrated, which promoted in vitro differentiation and in vivo functional muscle regeneration. This strategy offers a scalable and cytocompatible platform for generating aligned protein-based scaffolds with tunable mechanical and biological properties, thereby expanding the toolkit for regenerative medicine.