Pressure-sensitive composite bandages with high toughness, self-healability and strong tissues adhesion for rapid bone fixation and accelerated osteogenesis via immunomodulation and neovascularization

Bone adhesives have gained considerable interest as an adjunctive approach for fragment fixation in comminuted fractures and bone graft procedures. However, the current adhesives are mostly used to fill the bone void to achieve the fixation of broken bones, which inevitably impedes regeneration at the fracture interface. To address this limitation, we present an integrated bone-adhesive bandage that enables robust adhesion to bone tissue without occluding the healing space. Precise modulation of the viscoelastic properties in a poly(octamethylene citrate)-gelatin (POC-G) copolymer facilitates strong interfacial adhesion to bone but also unique internal cohesion to enable self-heal. Further incorporation of hydroxyapatite (HA) nanoparticles significantly enhances the adhesive strength (570.43 ± 21.82 kPa) while preserving mechanical toughness (1648.66 ± 367.81 kJ m^-3). This strategy further renders POC-G/HA composites with the unique ability to achieve instant, repeatable, and sustained bone fixation in a humid environment, addressing a critical limitation of conventional commercial adhesives. Beyond serving as a superior mechanical fixative, this multifunctional bandage actively orchestrates the bone regeneration process. It promotes the osteogenic differentiation of stem cells, modulates macrophage polarization towards a pro-regenerative M2 phenotype, and stimulates neovascularization to enhance local nutrient and cell supply. This breakthrough design of a pressure-sensitive bone-adhesive bandage opens a new avenue for the instant structural integration of bone fragments and the fixation of bone grafts during surgery. It represents a paradigm shift from passive fixation to active regeneration, potentially revolutionizing therapeutic strategies for bone repair.