Abstract
Nanopowders of hydroxyapatite (HA), modified by magnesium (MgHA) and by silicon (SiHA) were obtained by liquid-phase microwave synthesis method. X-ray diffraction and IR spectroscopy results showed that Mg2+ and SiO44− ions were present in the synthesized products both as secondary phases and as part of the HA phase. Whitlockite was found in the magnesium-modified HA (MgHA) and larnite was found in the silicon-modified HA (SiHA); ion substitution for both materials resulted in solid solutions. In the synthesized samples of modified HA, the increase of particle size of powders was in the order HA < SiHA < MgHA, which was calculated through data specific surface area and measured pycnometric density of the powders. The Lewis acid sites (Ca2+, Mg2+, Si4+) were present using spectral probes on the surface of the samples of HA, MgHA, and SiHA, and the acidity of these sites decreased in the order SiHA > MgHA > HA. The rates of calcium phosphate layer deposition on the surface of these materials at 37 °C in the model simulated body fluid solution showed similar dependence.
Highlights
The problem of finding material for implantation has existed since ancient times
This study investigated the crystalline phase, elemental composition, microstructure, and physicochemical and biomimetic properties of magnesium and silicon-modified hydroxyapatites that were prepared by liquid-phase microwave synthesis
Whitlockite was found to be present in the magnesium-modified HA (MgHA) and larnite was found to be present in the silicon-modified HA (SiHA); ion substitution for both materials resulted in solid solutions
Summary
Isomorphous substitutions in the phosphate-silicate system occurred with the formation of solid solutions of the substitution type, because in the crystallochemical aspect a tetrahedral oxygen environment is typical both for phosphorus (V) (rP5+ = 0,35 Å; rSi4+ = 0,39 Å) and silicon (IV). As it follows from the well-known ideas of interactions in isomorphous pairs of Са2+/Mg2+ and P5+/Si4, one can assume that the solid solutions formed in the MgHA and SiHA samples belonged to the substitution type. Phase Ca5(PO4)3OH Ca10(PO4)6(OH)[2] whitlockite Ca2,71Mg0,29(PO4)[2] larnite Са2SiO4
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