Synthesis and biological properties of thin-film materials on the basis of SiO2-P2O5-CaO-Na2 system

Thin films for the SiO2–P2O5–CaO–Na2O system are synthesized using sol-gel method. Content of the oxides in the system is 52-18-20-10 wt.% correspondingly. Thin films were produced from film-forming solutions on the single-crystal silicon substrates (model substrate) by extraction at a velocity of 5 mm/s following by heat treatment at a temperature of 60-80 °С for 20 minutes and at a temperature of 600 °С for 1 hour. During the experiment it was established that film-forming solutions are usable only for 2 to 7 days from the moment of preparation. Using thermal and infra-red – spectroscopic analysis main stages of oxide system formation were retraced. On the surface of the material NaCl, CaCl2, H2PO4·H2O, Ca5(PO4)3Cl, and SiO2 phases are being registered. Presence of the significant amount of pores leads to the essential increase in the specific surface area, creating optimal conditions for the new bone tissue formation. Biological activity of the received material was evaluated in SBF environment. Ca and P content on the surface of the material increased twofold in two weeks. Such material interchanges calcium ions and phosphate ions with solution; silanol groups fix calcium ions, furthering the formation of the layer of amorphous calcium phosphates gradually crystallizing in hydroxyapatite, and other calcium phosphates. Presence of magnesium and sodium on the surface of the samples after their immersion into SBF solution indicates the settling of SBF solution components on the film surface