Abstract
A calcium–phosphate system was obtained by sol–gel method from 0.4 M solutions based on ethyl alcohol, tetraethoxysilane, phosphoric acid, calcium nitrate, and magnesium nitrate, sodium chloride. Compositions with different contents of CaO, Na2O, and MgO were prepared. After maturation of the solutions, heat treatments were applied at 60 °C for 30 min; and followed by 600 °C and 800 °C for 1 h. Solution with 20 wt% MgO was found suitable for film production. The physicochemical processes of the formation of materials were studied, including the main stages: removal of physically bound and chemically bound water, combustion of alcohol and the products of thermo-oxidative destruction of ethoxy groups, and crystallization processes. The phase composition and structure of the films obtained were established at 600 °C and above when crystalline forms of SiO2, CaSiO3, Ca2P2O7, and complex phosphates were fixed. In the system with the addition of magnesium ions, β-cristobalite SiO2 and stenfieldt Mg3Ca3(PO4)4 were detected; however, a crystalline sample could only be obtained at 800 °C. In the system with sodium ions, chemical compounds Ca5(PO4)3Cl, NaCl, and SiO2 were determined. A uniform film coating was formed on the surface of the substrate. The introduction of sodium oxide into the SiO2–P2O5–CaO system increased the bioactivity of the materials obtained.
Highlights
The tasks of modern medicine and biotechnology include the creation of implants, the replacement of bone tissues and organs, and the synthesis of biologically active materials that contribute to the most complete tissue repair and the maintenance of necessary body functions (Barinov 2010; Dorozhkin 2010; Evdokimov et al 2014; Bagherpour et al 2018; Komlev et al 2012)
It is known that coatings based on calcium–phosphate are used to replace damaged bone tissue and they are characterized by high biocompatibility and biological activity with a Ca/P ratio in the range of 1.67 (Vallet-Regi and Gonzalez-Calbet 2004)
The stability of film-forming solutions (FFS) in time is important for the production of films
Summary
The tasks of modern medicine and biotechnology include the creation of implants, the replacement of bone tissues and organs, and the synthesis of biologically active materials that contribute to the most complete tissue repair and the maintenance of necessary body functions (Barinov 2010; Dorozhkin 2010; Evdokimov et al 2014; Bagherpour et al 2018; Komlev et al 2012). The bone system of a living organism is formed and maintained by complex biochemical reactions (Barinov 2010; Dorozhkin 2010). The main elements of these reactions are Ca, P, O, H, Na, and Mg. It is known that calcium is one of the important elements for a living organism: its cations control the transport of inorganic ions and organic substances through cell membranes in the exchange process associated with the entry. The system containing SiO2–CaO–P2O5–Na2O has a higher biological activity compared to hydroxyapatite. Magnesium is another key element that increases bioactivity. The magnesium ion proceeds as a silicate network modifier (Pet’kov et al 2006; Popa et al 2017)
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