PROBLEM TO BE SOLVED: To simplify the manufacturing process and enhance the modules of elasticity, toughness, and adaptability to vital organism by the subject material forming from silk proteins which are subjected to a chemical modification processing or graft processing.
SOLUTION: Silk proteins are subjected to a chemical modification processing or graft processing, and ionic radicals are coupled chemically with its reactive side chain. This imparts a function to absorb calcium and phosphoric acid effectively, and a bone bonding material with an enhanced bonding performance is accomplished. The ionic radical used in the reform is carboxyl radical such as of aspartic acid, glutamic acid, etc., and this absorbs calcium and phosphoric acid effectively and gives an ability to form hydroxy apatite in the material. The silk protein may be of natural origin, for example of house bred or natural bred. Thereby a material easy to adsorb calcium effectively can be obtained, becoming equivalent to a bone of vital organism substantially.