Zh. A. Ezhova

Gelatin-containing calcium hydroxyapatites: Synthesis and physicochemical characterization

The CaCl2-(NH4-)2HPO4-NH3-H2O-gelatin system was studied at 25°C using the solubility (residual concentrations) method. Stoichiometric nanocrystalline (11–15.4 nm) gelatin-containing calcium hydroxyapatites (HAs) were found to form. They were characterized by chemical analysis, thermal analysis, Xray powder diffraction, and IR spectroscopy.

Synthesis and physicochemical characterization of nanocrystalline chitosan-containing calcium carbonate apatites

The CaCl2-(NH4)2HPO4-NH4HCO3-(C6H11NO4)n-H2O system at 25°C has been investigated by the solubility (Tananaev’s residual concentration) method and pH measurements. Coprecipitation conditions have been determined for nanocrystalline type A and B calcium carbonate apatites. Type A: Ca10(PO4)6(CO3)x(OH)2 − 2x · yC6H11NO4 · zH2O (x = 0.2, 0.5, 1.0; y = 0.1, 0.3, 0.5; z = 5.3−6.7); type B: Ca10[(PO4)5.7(CO3)0.45]CO3 · 0.3C6H11NO4 · 9H2O, and Ca10[(PO4)5.55(CO3)0.675]CO3 · 0.3C6H11NO4 · 9.2H2O. The solid phases have been characterized by chemical analysis, X-ray diffraction, thermogravimetric analysis, and IR spectroscopy.

Synthesis and Physicochemical Study of Chitosan-Containing Calcium Hydroxylapatites

The CaCl2-(NH4)2HPO4-(C6H11NO4)n-NH3-H2O system at 25°C was studied by the solubility (Tananaev’s residual concentrations) technique and pH measurements. The parameters providing for the coprecipitation of nanocrystalline (12.5–18.7 nm) calcium and chitosan hydroxylapatites were found. Calcium-deficient chitosan hydroxylapatites Ca9.8(PO4)6(OH)1.6 · xC6H11NO4 · yH2O, where x = 0.075 or 0.37 and y = 5.8 or 6.2, and stoichiometric calcium hydroxylapatites Ca10(PO4)6(OH)2 · xC6H11NO4 · yH2O, where x = 0.075, 0.1, 0.2, 0.37, 0.5, or 0.75 and y = 5.7–7.5, were synthesized. Solid phases were characterized by chemical analysis, X-ray powder diffraction, thermogravimetric analysis, and IR spectroscopy.

Synthesis and physicochemical characterization of nanocomposites of calcium hydroxylapatite-chitosan-multiwall carbon nanotubes

The synthesis and physicochemical characterization of nanocomposites of calcium hydroxylapatite-chitosan-multiwall carbon nanotubes (CNTs) was performed. The CaCl2-(NH4)2HPO4-(C6H11NO4)n-CNT-NH3-H2O system was studied by the solubility (Tananaev’s residual concentration) method and pH measurements at 25°C. Conditions for the joint precipitation of nanocrystalline calcium hydroxylapatite, chitosan, and multiwall CNTs were found. Nanocomposites with the general formula Ca10(PO4)6(OH)2 · x(C6H11NO4) · yCNT · zH2O, where x = 0.1, 0.2, and 0.5; y = 0.5, 2.0, 4.0, and 5.0; and z = 5.9–7.9. The solid phases were characterized by chemical, thermogravimetric, and X-ray diffraction analysis and IR spectroscopy.

Calcium hydroxyapatite in hydroxyapatite/graphene oxide/collagen nanohybrids

Interactions between calcium and phosphorus salts, graphene oxide (GO), and collagen (COL) in aqueous solutions have been studied in the CaCl2–(NH4)2HPO4–NH3–H2O–GO–COL system (25°C) using the solubility (residual concentrations) method and pH measurements. Syntheses were shown to yield composites comprising nanocrystalline calcium hydroxyapatite Ca10(PO4)6(OH)2) (HA), GO, and COL of empirical formula Ca10(PO4)6(OH)2 · xGO · yH2O · zCOL (x = 0.5, 1.0, or 2.0; y = 6.5–7.7; z = 3 or 5 wt %). Some physicochemical characteristics of synthesis products and the effects of the composite formulation on the crystallographic characteristics, sizes, and morphology of nanocrystalline hydroxyapatite (NCHA) were determined and some composition–structure–dispersion–property relationships in the HA/GO/COL composites have been analyzed using chemical analysis, X-ray powder diffraction, IR spectroscopy, thermogravimetry (TGA), differential scanning calorimetry (DSC), and electron microscopy.

Synthesis and physicochemical characteristics of calcium hydroxyapatite/multiwall carbon nanotubes/collagen nanocomposites

Calcium hydroxyapatite/multiwall carbon nanotubes/collagen nanocomposites were synthesized and subjected to physicochemical analysis. The system CaCl2-(NH4)2HPO4-multiwall carbon nanotubes-NH3-H2O-collagen was investigated at 25°C by the solubility method (Tananaev’s residual concentration method) and by pH measurements. Chemical, X-ray powder diffraction, and thermogravimetric analyses and IR spectroscopy showed that, in the system CaCl2-(NH4)2HPO4-multiwall carbon nanotubes-NH3-H2O-collagen under chosen synthesis conditions, nanocomposites comprising nanocrystalline calcium hydroxyapatite (NCHA), multiwall carbon nanotubes (CNT), and collagen form with the composition Ca10(PO4)6(OH)2 · xCNT · yH2O · z collagen, where x = 1–5; y = 5.5–7.7, and z = 3, 5, and 10 wt %. The obtained nanocomposites are the products of the coprecipitation of CNT, collagen, and NCHA, which forms in the system by the interaction of CaCl2 and (NH4)2HPO4.

Synthesis and physicochemical properties of calcium hydroxylapatite/multi-walled carbon nanotubes nanocomposites

Calcium hydroxylapatite/carbon nanotubes (HA/CNT) composites with various CNT contents have been synthesized by coprecipitation from aqueous solutions in the CaCl2-(NH4)2HPO4-NH3-CNT-H2O system (25°C) under conditions modeling the interaction between HA (Ca10(PO4)6(OH)2), which is an inorganic component of osseous tissue, and multi-walled CNTs. The empirical formula of the composites is Ca10(PO4)6(OH)2 · nCNT · 6H2O, where n = 0.2–5.0. The synthesis products have been identified by the solubility (Tananaev’s residual concentration) method, pH measurements, chemical analysis, X-ray diffraction, IR spectroscopy, electron spectroscopy for chemical analysis, and scanning and transmission electron microscopy. The effect of the CNT concentration in aqueous solution on the composition of the HA/CNT composites and on the crystallographic and morphological characteristics of HA nanocrystals in HA/CNT has been investigated.

Synthesis and physicochemical study of nanocrystalline magnesium-containing calcium hydroxylapatites and chitosan

The interaction in the CaCl2-MgCl2-(NH4)2HPO4-NH3-H2O and CaCl2-MgCl2-(NH4)2HPO4-(C6H11NO4)n-NH3-H2O systems at 25°C has been investigated by the solubility (Tananaev’s residual concentration) method and by pH measurements. Magnesium-containing calcium hydroxylapatites with the general formula MgxCa10 − x(PO4)6(OH)2 · nH2O (x = 0.05, 0.1, 0.2, 0.3; n = 6–7.3) and magnesium- and chitosan-containing calcium hydroxylapatites with the general formula MgxCa10 − x(PO4)6(OH)2 · y(C6H11NO4) · nH2O (x = 0.05, 0.1, 0.2, 0.3; y = 0.1, 0.3, 0.46; n = 6–8.3) have been isolated in the nanocrystalline state. The solids have been characterized by chemical and thermogravimetric analyses, X-ray diffraction, and IR spectroscopy.

Synthesis and physicochemical characteristics of the calcium hydroxyapatite/graphene oxide hybrid nanocomposite

The system CaCl2-(NH4)2HPO4-NH3-H2O-graphene oxide (25°C) was studied by the solubility method (Tananaev’s residual concentration method) and by pH measurements and was used to model in vitro the biomineralization of the main inorganic component of the bone tissue—calcium hydroxyapatite (HA) Ca10(PO4)6(OH)2—in the presence of a nanosized modification of carbon—graphene oxide (GO). It was shown that the synthesis in the system produces hybrid composite materials (CM) of the general composition Ca10(PO4)6(OH)2 · xGO · yH2O, where x = 0.5, 1.0, and 2.0 and y = 7.4–7.7, which contain GO and nanocrystalline (NC) HA of the stoichiometric composition. By chemical analysis, X-ray powder diffraction analysis, IR spectroscopy, thermogravimetric analysis, and differential scanning calorimetry, the main physicochemical characteristics of the synthesis products were determined, the effect of the composition on the crystallographic parameters, sizes, and morphology of NC HA in HA/GO CM was evaluated, and the main composition-structure-dispersity-properties relationships for the synthesized HA/GO CM were analyzed.

Synthesis and physicochemical characterization of carboxymethylcellulose-containing calcium hydroxylapatite

The CaCl2-(NH4)2HPO4-C8H11O7Na-NH3-H2O system was studied at 25°C using the solubility method (Tananaev’s residual concentration method) and pH measurements. The solid phases isolated from the system were characterized using chemical analysis, X-ray powder diffraction, IR spectroscopy, and thermogravimetry. Nanocrystalline carboxymethylcellulose-containing calcium hydroxylapatites Ca10(PO4)6(OH)2 · xH2O · yC8H11O7Na with x = 6–12 and y = 0.1–0.5 were found as a result of the characterization.