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The problems of modern medicine and biotechnology involve not only creation of implants replacing bone tissues and organs, but also synthesis of biologically active materials promoting the fullest restoration of tissues and maintenance of necessary functions of an organism. It is well known that calcium is one of the elements important for a living organism, for its cations control the transportation of inorganic ions and organic substances through cell membranes in the metabolic process involving the delivery and removal of reaction products from a cell. Interacting with regulatory proteins, calcium participates in nerve impulse transmission to muscles. Calcium is necessary for blood coagulation and participation in the synthesis of hormones, neuromediators and other controlling substances (1). Calcium is a building material for the bone tissue, its inorganic part. The solid residual of the bone tissue contains 70 % of calcium hydroxide phosphate (calcium hydroxyapatite) Ca10(PO4)6(OH)2 and 30 % of an organic component, namely, collagen fiber. The bone tissue should be characterized as an organic matrix impregnated by amorphous Ca3(PO4)2 and crystals of calcium hydroxide phosphate synthesized in bone tissue osteoblast cells (2). Ions Na+, K+, Mg2+, Fe2+, Cland C《32are contained in the structure of calcium hydroxide phosphate of the bone tissue besides 』а2+ and 『《43-. The content of anions 』《32in calcium hydroxide phosphate of the bone material can make up to 8 wt. %, and they substitute hydroxyl or phosphate groups. Therefore, in view of the carbonate groups introduced into the structure of calcium hydroxide phosphate, its probable formula will be as follows (3 – 5): Ca10(PO4)6(CO3)x(OH)2-x. Actually, the crystal structure, as well as the structure of chemical bonds, of calcium hydroxide phosphate is much more complex because of vacancies in the crystal structure of both anion and cation nature. The vacancies can be filled with bivalent cations of trace elements received by a living organism and with anions SiO2x 2-, SO42and Cl-, F-. The crystal structure of calcium hydroxyapatite is considered in (4, 5) where there is a simplified form of an elementary cell. However, practically in all scientific works accessible for viewing it is |
