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.
The microstructure and magnetic properties of Fe-3.5Si-1.5Al (mass%) steel fabricated by laser-directed energy deposition (L-DED) were investigated. Scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) analyses revealed that the specimens consisted of coarse columnar grains extending across melt pool boundaries. A pronounced <001> crystallographic texture aligned with the build direction was also observed, indicating epitaxial grain growth. The direct current magnetic properties, evaluated using a single-sheet tester, showed a strong dependence on the measurement direction relative to the crystallographic texture. The vertical test piece (VTP), in which the measurement direction was parallel to the <001> texture, exhibited the highest magnetic flux density at 800 A/m (B8), the lowest coercivity (H-C), and the lowest hysteresis loss. In contrast, the horizontal test pieces, whose measurement direction was perpendicular to the <001> texture, exhibited inferior magnetic properties. These results indicate that the superior soft magnetic properties of the VTP originate from the alignment of the <001> texture with the measurement direction, corresponding to the easy magnetization axis of ferritic steel. The present study demonstrates that texture control through the L-DED process is essential for improving the electromagnetic properties of Fe-Si-Al steel.
