Bioactive Phosphate Glass-Based Biomaterials Design for Bone Regeneration: Metal-Ion Release and Anisotropic Scaffold Approaches

Bioactive glasses, which can release therapeutic metal ions, have attracted attention due to their ability to stimulate osteogenic differentiation, angiogenesis, and antibacterial activity. Recently, biomaterials have shifted toward bioadaptive materials that actively regulate cellular behavior by the material. In our group, phosphate invert glasses were focused on controlled metal-ion release materials for bioadaptive materials. The glasses can control their ion release behavior by designing the glass network structure using intermediates. These design strategies enable tailored ion-releasing behavior for enhanced osteogenesis and infection control. Bone tissue exhibits a highly anisotropic structure. The collagen fibrils and the c-axis of the apatite crystal are aligned. Anisotropic structure is the key to the bone quality and mechanical strength. Bone quality correlates more strongly with mechanical properties than bone mineral density, particularly during early-stage bone regeneration. Therefore, reconstructing anisotropic bone structure is essential for functional bone reconstruction. The combination of bioactive glasses with electrospinning, fiber-aligned scaffolds effectively controls osteoblast alignment and apatite c-axis orientation, leading to improved bone matrix anisotropy. This review presents recent progress in the development of therapeutic metal ion-releasing bioactive phosphate glass-based biomaterials for bone regeneration, and anisotropic fibrous scaffolds aimed at the simultaneous regeneration of bone quantity and quality.