Bone Substitute Materials

Bone Substitute Materials

Bone substitutes are widely used to repair bone defects caused by fractures, disease, or surgery. An ideal bone substitute should be biocompatible and gradually replaced by the patient’s own bone while providing sufficient mechanical support during the healing process. However, conventional materials such as metals and ceramics have limitations, including excessive stiffness, brittleness, and limited biodegradability. Therefore, we are developing bone substitute materials derived from natural biological resources that combine biological affinity with appropriate mechanical properties.

One material of particular interest is calcined bone. Calcination removes organic components from animal bone, reducing immunogenicity and infection risk while preserving the mineral phase of bone. The resulting material mainly consists of biological apatite and has excellent potential as a biocompatible and biodegradable bone substitute. However, removal of collagen during calcination makes the material brittle and limits its use in mechanically demanding applications.

To overcome this limitation, we developed a composite consisting of calcined bovine bone powder and silane cross-linked alginate, a naturally derived polysaccharide. In this composite, calcined bone particles provide mechanical rigidity, while the alginate network contributes fracture resistance and stability. Silane cross-linking further improves stability in physiological environments and promotes apatite formation. Our studies aim to develop mechanically compatible, biocompatible, and osteoconductive materials that can ultimately be integrated with and replaced by newly formed bone.

Cultured osteoblasts showed no cytotoxicity and exhibited general cell proliferative properties in its presence. The composite reduced the alkaline phosphatase activity of osteoblasts but led to significant non-cellular apatite deposition on the surface. The mechanical properties did not deteriorate significantly even after two weeks of immersion in simulated body fluid at 37 C.