Ultrafast crosslinking, strongly adhesive de novo protein hydrogels promote cartilage regeneration

Osteoarthritis (OA) is a prevalent degenerative joint disease and the leading cause of chronic pain and disability, affecting millions of people worldwide. In the early stages, shallow cartilage lesions serve as the primary pathological driver, leading to progressive cartilage deterioration and the development of OA. These lesions are characterized by irregular shape and depth, with an inherent anti-adhesive extracellular matrix (ECM), and a poor niche for tissue regeneration, currently lacking effective clinical interventions. Despite extensive efforts, few tissue engineering-based therapies simultaneously address both the demands of robust adhesion to host tissue, support for cell adhesion, and promotion of regeneration for partial-thickness cartilage defects. Here, we report a <i>de novo</i> engineered protein adhesive hydrogel that displays ultrafast gelation, robust tissue adhesion, and maintains chondrocyte phenotype. Tyrosine, lysine, and RGD motifs were precisely encoded into the protein backbone by genetic engineering to enable visible light-triggered covalent bonding, electrostatic interactions with negatively charged cartilage ECM, and enhanced cell adhesion. Molecular weight was tailored by extending monomer repeats to further improve the mechanical performance. Importantly, this genetically engineered protein hydrogel demonstrated ultrafast gelation (<2 s), high adhesive strength (90.8 ± 1.8 kPa), excellent biocompatibility <i>in vitro</i> and <i>in vivo</i>, and supported chondrogenic maintenance. These hydrogels also promoted hyaline-like cartilage matrix regeneration in the partial-thickness cartilage defect rabbit model. Overall, our findings present a bottom-up protein engineering strategy for developing multifunctional adhesive hydrogels, offering a promising translational platform for musculoskeletal disease treatment, in particular cartilage repair.