Fig. 1: Design and working mechanisms of the SF/MgO composite scaffolds for minimally invasive clinical-size irregular bone regeneration.

a Preparation process of the SF/MgO composite scaffolds and its mechanism of cross-linking reaction: the epoxy group of EGDE reacts with the phenyl hydroxyl and amino groups from SF, and the SF molecules form a physically cross-linked network via the β-sheet domains; electrostatic interactions occur between the negatively charged SF and positively charged MgO particles; according to the mass ratio of the nano-MgO particles to the solute mass of the SF solution at 0 wt%, 10 wt% and 30 wt%, named SF, SF-1nMgO and SF-3nMgO, respectively. b The SF/MgO composite scaffolds are tailored to the actual needs of clinical surgery; after being implanted, the cell-free SF/MgO composite scaffolds are recovered by a water-responsive shape-memory effect, resulting in tight contact with the surrounding tissue; the Mg²⁺ is released slowly from the SF/MgO scaffolds to regulate the functions of migrating cells, including adhesion, proliferation and vascularisation, and to promote the expression of related osteogenic genes (runt-related transcription factor 2 (Runx2), osteocalcin (OCN), osteopontin (OPN) and collagen I (COL I)); finally, the defective bone is repaired in situ.