Tough Anisotropic Silk Nanofiber Hydrogels with Osteoinductive\nCapacity

Abstract

Multiple physical\ncues such as hierarchical microstructures, topography,\nand stiffness influence cell fate during tissue regeneration. Yet,\nintroducing multiple physical cues to the same biomaterial remains\na challenge. Here, a synergistic cross-linking strategy was developed\nto fabricate protein hydrogels with multiple physical cues based on\ncombinations of two types of silk nanofibers. β-sheet-rich silk\nnanofibers (BSNFs) were blended with amorphous silk nanofibers (ASNFs)\nto form composite nanofiber systems. The composites were transformed\ninto tough hydrogels through horseradish peroxidase (HRP) cross-linking\nin an electric field, where ASNFs were cross-linked with HRP, while\nBSNFs were aligned by the electrical field. Anisotropic morphologies\nand higher stiffness of 120 kPa were achieved. These anisotropic hydrogels\ninduced osteogenic differentiation and the aligned aggregation of\nstem cells in vitro while also exhibiting osteoinductive capacity\nin vivo. Improved tissue outcomes with the hydrogels suggest promising\napplications in bone tissue engineering, as the processing strategy\ndescribed here provides options to form hydrogels with multiple physical\ncues.