Certain types of ceramics have property that shows direct bonding to living bone tissue in vivo, and are referred to as bioactive materials. As a bioactive material, Bioglass^® was discovered and developed in early 1970’s, inorganic glasses and materials based on them have been studied for bone substitutes for tissue repairing. In addition, elucidation of the mechanism by which they express their high biological affinity has been studied. The author has been interested in elucidating the mechanisms by which inorganic glasses show high biological affinity to bond to living bone, and has carried out fundamental research, as well as developing novel biomaterials based on the materials chemistry of glasses and ceramics. The science and technology of the bioactive glasses have made a significant contribution to the field of medicine. Whilst, 2022 has been designated as the International Year of Glass by the United Nations General Assembly, and events commemorating the science, technology and art associated with glass are being held around the world. As part of these events, a special feature on glass science and bioinspired materials was also held at the 2022 Spring Meeting of the Japan Society of Powder and Powder Metallurgy. Against this background, this paper describes the review of the author’s achievement awards, with a particular focus on glass and biomaterials, and the development of novel materials using bioinspired methods.

In this review, the current status and issues of bone defect sites in our body were explained based on the examples of the conventional hydroxyapatite (HA), and the necessity of regenerative functions in addition to bone defect sites for the biomedical applications was proposed. The characteristics and properties of HA substituted with the heterogeneous ions such as silicate, carbonate and other elemental ions were explained. For the effective control of the biomedical function, the characteristics and possibilities of the surface layer formed on HA and its components, the hydrated layer and the non-HA layer were proposed, and their relationship for improving the biocompatibility was highlighted.

Calcium phosphate cements (CPCs) with macropores and micropores for high bone regeneration ability are desired. CPCs with macropores and micropores which were prepared by combining porous granules have been reported. In this study, the cement system composed of β-tricalcium phosphate (β-TCP) granules and phosphoric acid solution was selected, and the effects of the characteristics of granules on the microstructures and properties of the cements were examined. The spherical porous β-TCP granules with high porosity and irregular porous β-TCP granules with low porosity were prepared, and they were mixed with a phosphoric acid solution. When the spherical porous granules with high porosity were used, the granules were packed uniformly in the cement, and the size distribution of the macropores formed among the granules was narrower than that of the cement prepared using the irregular porous β-TCP granules with low porosity. The cement with high porosity can be obtained from the spherical porous granules with high porosity. The cement prepared using the spherical granules with high porosity showed lower compressive strength and higher dissolution rate than the cement prepared using irregular granules with low porosity.

Bone cement is applied to bone detect caused by injury and disease. Our group has developed a novel bone paste by kneading a gelatinized wheat starch and calcium phosphate (CP) powders in which CaHPO₄, Ca₄(PO₄)₂O and β-Ca₃(PO₄)₂ are equimolarly mixed. This bone paste is easily handled and can be set to form hydroxyapatite (HAp) under physiological conditions. On the other hand, previous literature reported that strontium ion can promote and regulate the activity of osteoblastic and osteoclastic cells in the living bone, respectively. In addition, copper ion is reported antibacterial performance. In this work, strontium and copper ions were fed into the bone paste as starting materials to promote cell activity as well as antibacterial properties. Paste samples were prepared by kneading a starch gelatinized with mixed powders of CP, α-SrHPO₄ and Cu²⁺-substituted β-Ca₃(PO₄)₂. Phase change, release behavior of metal cations and antibacterial properties were investigated. A paste sample immersed in Tris-buffered NaCl solution was set through forming HAp, and the amount of strontium ion released from the paste sample was a level expected to enhance the cell activity. However, all the pastes didn’t show antibacterial properties in spite of introducing of copper ion to the samples.

Amorphous calcium phosphate (ACP) is known as a precursor of hydroxyapatite (HAp) which is an inorganic main component of bone. The ACP gradually crystallizes to low crystalline apatite near human body temperature. If we introduce an active ingredient at the time of synthesis of ACP and we can introduce an ingredient effective for bone repair or an ingredient having functionality into the crystal structure of HAp, an active ingredient-releasing material responsive to bone metabolism would obtaine, and the protein might produce. Mn is an essential trace element in the living body and is present in the body as an active metal such as Mn-SOD (Mn-superoxmutase) having an antioxidant activity and enhancing the activity of proteoglycan synthetase during bone formation. In this research, we try to introduce Mn into ACP, prepare cement using the obtained powder. In the synthetic powder, Mn was introduced at the same rate as the preparation. The obtained cement had crystallized and low-crytalline bone-like apatite composition. The porosity changed with the amount of Mn added. The cements exhibited protein adsorption properties regardress of the addition of Mn. It is expected that proteins involved in bone metabolism adsorb to the cement.