Microstructural Anisotropy in Bone-Mimetic Silk Constructs Promotes Self-Mineralization.

Abstract

Understanding how organic matrix architecture regulates biomineralization remains a central challenge in mineralized tissue regeneration. Emerging evidence highlights the importance of coupled phenomena, including nanoconfinement, ionic and pH regulation, and hierarchical structural remodeling, in directing mineral formation. Silk fibroin (SF) is a versatile structural protein widely used in biomaterials due to its tunable mechanics, scalable processing into micro- and nanoscale constructs, controllable biodegradation, and ability to support cell infiltration and tissue integration, including in bone. However, despite its favorable biological properties, SF exhibits limited intrinsic self-mineralization in physiological fluids, restricting its mechanical reinforcement and osteogenic potential. In this study, we engineered SF scaffolds with controlled microstructure and anisotropy and incorporated bioactive inorganic phases, nano-hydroxyapatite (HA) or 45S5 bioactive glass (BG) to promote self-directed mineralization. Scaffolds were evaluated in simulated body fluid under static and dynamic conditions to assess mineral formation and distribution. Isotropic architectures supported more uniform, volumetric mineral integration, whereas anisotropic scaffolds promoted preferential surface mineral deposition. Incorporation of HA or BG significantly enhanced mineralization, leading to the formation of carbonate-substituted hydroxyapatite (CHA). These compositional and structural effects translated into marked improvements in compressive mechanical properties. Collectively, these findings demonstrate that synergistic control over scaffold architecture and bioactive cargo can direct in situ mineralization, enabling the design of silk-based constructs with enhanced mechanical performance and potential for bone regeneration.