Biomimetically anisotropic hierarchical scaffold mediating stress transmission along the direction of force loading for rapid bone regeneration.

Abstract

The mechanical conduction of artificial bone scaffolds, predominantly governed by the scaffold structure, significantly influences their osteogenic capacity. Although various meticulously designed scaffold structures can enhance the osteogenic ability of scaffolds, systematic examination integrating scaffold structure, stress transmission, osteogenic performance, and underlying mechanisms is still not available. Against this backdrop, achieving a gradient change in stress transmission within the scaffold was identified as a key objective. Anisotropically and hierarchically porous scaffolds with continuous oriented structures were fabricated with a subatmospheric-pressure-guided anti-solvent phase separation method. As the angle between the orientation direction of the scaffold and the loading direction changes gradually, the stress transmission capacity of the scaffold varies correspondingly and the best osteogenic effect occurs when the orientation direction of the scaffold aligns with the loading direction, as this case results in the most uniform stress distribution, the maximum total strain the fastest stress relaxation, the strongest anelastic recovery, and the minimal creep. This means the scaffold provides the maximum stress stimulation to adherent cells and offers the strongest support in the course of deformation. Overall, the design of hierarchical pore structures aligned with the loading direction in artificial bone scaffolds enables efficient stress transfer to adherent cells during the deformation of the scaffolds, thereby effectively promoting new bone formation. Thus, this study offers a scientific foundation for the structural design of artificial bones and enriches the theoretical framework of mechanically-induced osteogenesis.