Carbonate hydroxyapatite composites were synthesized from model media with different contents of high- molecular hyaluronic acid. The dynamics of their dissolution in acetate buffer solution and 0,9 % sodium chloride solution was studied. It was shown that all powders are more soluble in weakly acidic conditions. Their resorption rate depends on the degree of apatite crystallinity and the polysaccharide content in the initial solution. The results of powder cytotoxicity tests on the FetMSC cell line using the MMT test are presented. It was found that the composites have an insignificant cytotoxic effect on cultured cells. Cell viability improves with a longer period of sample incubation. Composites dissolving at an average rate in physiological solutions exhibit a consistently positive effect on cells. The obtained composites are promising as non- toxic materials for accelerating implant bioresorption involving osteoclasts in vivo.

Lanthanide-doped hydroxyapatite nanoparticles can be used as luminescent labels and become an alternative to organic fluorophores, as they are more stable and have a longer service life. Such materials allow tissue studies in surgery, the bone engineering and tissue regeneration. Lanthanides are known to have a high affinity for hydroxyapatite. This is due to the fact that lanthanides have ionic radii close to that of the calcium ion which is associated with their biological activity. Rare earth elements inhibit the formation of osteoclast-like cells and the process of the bone resorption. At the same time, lanthanides have a biological effect on the body, as a result bacterial growth is suppressed and, at the same time, the structure of the outer cell membrane, responsible for cell permeability, changes. Substituted hydroxyapatites were synthesized with varying content of the lanthanum (III) and cerium (III) ions. The formation of substituted hydroxyapatite was proven by X-ray diffraction and infrared spectroscopy. The parameters of the crystal lattices of the synthesized phases were shown to change, indicating the replacement of calcium ions by rare earth element ions in the hydroxyapatite structure. The presence of rare earth element ions in solid phases was proven by inductively coupled plasma atomic emission spectroscopy. The study of the resorption of thesynthesized samples revealed that cation-substituted hydroxyapatites are less soluble than unmodified hydroxyapatite. Thus, lanthanum (III) and cerium (III) ions can inhibit and suppress the action of osteoclasts and thereby prevent the destruction of the bone tissue maintaining its integrity. Accordingly, the material based on hydroxyapatite dosed with rare earth element ions can have a positive effect when used in bone engineering.

Composites based on hydroxyapatite and natural biopolymers are promising materials for bone grafting. In this work, samples of hydroxyapatite were synthesized by chemical precipitation from aqueous solutions in the presence of high molecular weight hyaluronic acid (0,4-0,8 wt.%). The resulting powders are represented by carbonate-containing nanohydroxyapatite and contain 89-98 wt.% of polysaccharide. A correlation has been established between the content of hyaluronic acid in the mother solution and the crystal chemical, structural and morphological characteristics of the samples. It was revealed that, in comparison with the hydroxyapatite sample, in viscoelastic media of the polysaccharide, powders are formed that have a smaller parameter a of the hydroxyapatite crystal lattice, close in value to the stoichiometric phase. With an increase in the content of hyaluronic acid in the mother solution, the crystallinity, crystallite sizes and specific surface area of the composites decrease; their average value is 16 nm and 47 m2/g. Samples based on nanohydroxyapatite and polysaccharide consist of oval-lamellar agglomerated particles. At the maximum content of hyaluronic acid in the model solution, amorphized round conglomerates, dense in structure, are formed. The synthesized composites can be used in medical practice as osteoconductive implants, as well as to create nanoencapsulated drug delivery systems.

This study deals with a search for relationships between the composition and properties of CaCO3 in bile and amino acid concentrations in it. Twenty two calcium carbonate samples were synthesized in bile by varying the concentrations of the amino acids histidine (His), methionine (Met), arginine (Arg), and tryptophan (Trp). It was found by thermodynamic modeling that the introduction of amino acids increases the stability of bile due to the reduction of the mole fraction of free Ca2+ ions. The CaCO3 content in the solid phase of the synthesized samples was determined; the maximum content was found for the samples obtained with Arg, and the minimum one, for those obtained with Met. The X-ray diffraction (XRD) analysis and Fourier transform IR spectroscopy studies showed that all the resulting powders were based on vaterite. For the amino acids Met and Arg, their stabilizing effect in relation to metastable aragonite was proved. Optical microscopy showed the presence of vaterite spherulites in all the resulting powders. It was established by photon correlation spectroscopy (PCS) that calcium carbonate microparticles with a radius of less than 10 μm are represented by three fractions. All the amino acids under study can be used as medicines for treatment and prevention of microcholelithiasis.

Structural models of magnesium compounds with valine and glycine have been constructed. MP2 and DFT (B3LYP functional) methods in the 6-31G(d) basis were used for the construction. The frequencies of normal oscillations in the IR spectrum of the models have been calculated. Comparison of the calculated IR spectra with each other and with the spectra of the synthesised compounds is shown. Conclusions about the structure of the compounds are drawn. The obtained data on coordination of magnesium compounds with amino acids can help to establish the structure of their complexes.

Synthesis of magnesium(II) complexes with lysine and isoleucine from aqueous solutions of magnesium chloride and respective amino acids was carried out. The content of amino acids in the synthesized compounds was determined by formol titration using the Searnsen method. The content of magnesium(II) ions was determined by complexometric titration. The IR spectra of the synthesized compounds were recorded in the range of 500-4000 cm(-1). Structural dynamic models of magnesium lysinate and Magnesium isoleucinate complexes were simulated by the method density- functional theory (DFT, v B 3LYP) in the 6-31G and 3-21G basis sets. The molecular geometric parameters and frequencies of normal vibrations within the harmonic approximation in the IR spectra of the developed models were calculated. The calculated and experimental IR spectra of the synthesized compounds were compared in order to validate their structures. Data on coordination of compounds of magnesium ions with amino acids contributes to reliably establish the structure of their poorly studied complexes and can also allow to improve the methods for the synthesis of these complex compounds of predetermined composition and structure.

The synthesis of magnesium compound with tryptophan was carried out. The ratio of magnesium and amino acid in the obtained compound was determined by complexometric titration and formol titration according to the Serensen method. The infrared spectra of the synthesized compound measured in the range of 500-4000 cm-1 are presented. The compound was analyzed by Xray diffraction method. The diffractograms of the investigated compound are presented. The volume and unit cell parameters by dichotomy method, interplanar distances, average particle size by Selyakov-Scherrer method, Miller indices were calculated for the obtained compounds. A model of magnesium tryptophanate compound was constructed using quantum-chemical methods: Hartree-Fock and density functional ( B3LYP ) in the 6-31G(d,p) basis. The energy minimized, the normal vibrational frequencies of the infrared spectrum of the model infrared spectrum of the investigated compound were calculated. The calculated and experimental infrared spectra of the investigated compound were analyzed. The obtained data contribute to the development of the science of complex compounds, improvement of methods of synthesis of compounds of a given composition. The possibility of further use of such compounds as drugs is also discussed.

The effects of high- molecular hyaluronic acid on the phase composition, crystal lattice parameters, and the sizes of the regions of coherent dispersion, depending on its content in the synthesis solution, have been studied. All composites are represented by poorly crystallized carbonate hydroxyapatite. With an increase in the viscosity of the medium, the broadening of the parameter a of the hydroxyapatite crystal lattice decreases and the most crystallized precipitates are formed, the average size of the crystallites is similar to 15 nm, the specific surface area of the samples does not change (105-130 m(2)/g).

The kinetic regularities of crystallization (its order and constants) in a model solution of human synovia (inorganic composition) under conditions close to physiological have been investigated. The crystallization constants in a pure solution and in the presence of organic synovia additives with variation in their concentration and supersaturation of the model solution are determined. The following descending order sequence is proposed for the influence of additives on the general and particular kinetic characteristics of crystallization in a model synovial solution: glucose → proline → alanine → glycine → citric acid. It is found that impurities affect to a greater extent the nucleation process rather than growth stages.

Structural dynamic models of magnesium glycinate and magnesium tyrosinate complexes were simulated by the method of density-functional theory (DFT) using the B3LYP functional in the 6-31G(d,p) and 6-31G basis sets. The molecular geometric parameters and frequencies of normal vibrations within the harmonic approximation in the IR spectra of the developed models were calculated. Magnesium(II) complexes with glycine and tyrosine were synthesized from aqueous solutions of the corresponding salts of magnesium chloride and the amino acid. The content of amino acids in the synthesized compounds was determined by formol titration using the Sørensen method. The content of magnesium(II) ions is determined by complexometric titration. The IR spectra of the synthesized compounds were recorded in the range of 500–4000 cm–1. The calculated and experimental IR spectra of the synthesized magnesium(II) complexes with glycine and tyrosine were compared in order to validate their structures. Data on the coordination of calcium and magnesium ion complexes with amino acids contributes to understanding the structure of these poorly studied complexes and improving methods for obtaining these complex compounds with a predetermined composition and structure.

Currently, the global demand for orthopedic implants exceeds 6 million units per year and continues to increase. It is known that human bone is a composite material, the inorganic part of which is formed by calcium phosphates, mainly in the form of hydroxyapatite of non-stoichiometric composition. This fact determines the interest in studying the possibility of using hydroxyapatite-based materials for biomedical purposes, which are similar to the chemical composition of the bone and dental tissues and have high biocompatibility. Research in this area is necessary from both the fundamental perspective for expanding the scope of the method, and in view of development of new materials and studying biological fluids in health and pathology. The work shows that the presence of organic and inorganic additives in the synthesis of hydroxyapatite affects the composition and morphology of the crystals of the resulting compound. The results of analysis, presented in the form of diagrams, allow us to judge the inversely proportional relationship between the crystallization time and the value of the morphological dimension of the hydroxyapatite structures, regardless of the nature of the additive. The results obtained confirm the possibility of using morphological analysis to establish the patterns of formation of hydroxyapatite-based materials and to perform an express assessment of their properties (composition, morphology, degree of crystallinity, nature and concentration of impurities).

Substituted hydroxylapatites (HAs) containing various La3+ or Y3+ percentages were prepared. X‑ray powder diffraction, Four-transform IR spectroscopy, and optical spectroscopy verified the formation of substituted hydroxylapatites (La–HA and Y–HA). Inductively coupled plasma atomic emission spectrometry (ICP–AES) verified the presence of REE ions in the solids. Changes in the unit cell parameters of the prepared phases indicated that the REE ions substituted for Ca2+ ions in the hydroxylapatite structure. The lanthanum or yttrium percentage in precipitates increased in response to increasing REE salt concentration (within 1–5 wt %) in the initial solution as shown by chemical analysis; this brought about a decrease in the ratio Ca/P compared to the stoichiometric ratio (1.67). The solubility of the synthesized samples was studied, and it appeared that the cation-substituted hydroxylapatites were less soluble than undoped HA was.

In this paper, we studied the effect of amino acids in the composition of bile, the formation of various modifications of calcium carbonate (aragonite, vaterite, calcite). In this work, 22 samples of calcium carbonate in bile were synthesized by varying the concentrations of amino acids (histidine, methionine, arginine and tryptophan). For the amino acids methionine and arginine, their stabilizing effect with respect to metastable aragonite has been proven: with an increase in their concentration in bile, an increase in the mass fraction of aragonite in the composition of the solid phase occurs. Optical microscopy showed the presence of vaterite spherulites in all obtained powders. The results of photon correlation spectroscopy correlate with the data of X-ray phase analysis. It is shown that calcium carbonate microparticles with a radius of less than 10 mu m are represented by three fractions. It has been shown that syntheses involving histidine and tryptophan, in which, with increasing amino acid concentrations, an increase in the proportion of the small-sized fraction and a decrease in the proportion of the large-sized ones are observed. Thus, all studied amino acids have the potential to be used as medicines for the treatment and prevention of nanocholelithiasis.

For the first time, a physicochemical model of the formation of poorly soluble compounds in the kidney nephron was developed on the basis of a mathematical description of the ideal displacement reactor. As a result of mathematical modeling, it was found that under normal physiological conditions, the formation of a solid phase is not the dominant process, which explains the absence of crystalline formations in the kidneys in healthy people. An increase in the concentration of precipitate-forming ions, corresponding to certain conditions of the human body, leads to the occurrence of local high supersaturations in certain areas of the nephron, which can lead to the formation of solid phase nuclei, their fixation and further growth. It is shown that the calculations of material balances, flow movements, as well as the concentration profiles of components in the nephron determine the possibility of predicting the behavior of the model system with variations in the parameters and conditions that affect the course of the crystallization process (concentration, fluid flow, hydrodynamic regime, etc.), which will allow developing effective methods for the prevention and treatment of urolithiasis, including the dissolution of already formed aggregates.

Composites based on a mixture of calcium phosphates and hyaluronic acid (HA) have been synthesized, the properties of which can be adjusted by varying the filler/matrix ratio and the drying temperature, which makes it possible to consider the obtained materials promising for use in medicine. We investigated their composition, morphology, and dynamic dissolution behavior. The addition of a powder material to the matrix hyaluronic acid causes no changes in its composition, but increases resorption rate of the sample. We have optimized the synthesis conditions of the composite: the filler/ matrix ratio and the drying temperature and time.

Structural dynamic models of magnesium glutamateMagnesium glutamate and calcium glutamateCalcium glutamate complexes were simulated by the methods of Hartree–Fock (HF) and density-functional theoryDensity-functional theory (DFT, v B3LYP) in the 6-31G and 3-21G basis sets. The molecular geometric parameters and frequencies of normal vibrations within the harmonic approximation in the IR spectraIR spectrum of the developed models were calculated. Calcium (II) and magnesiumMagnesium (II) complexes with glutamic acid were synthesized from aqueous solutions of the corresponding salts of calcium chloride and magnesiumMagnesium chloride, and the amino acid. The IR spectraIR spectrum of the synthesized compounds were recorded in the range of 500–4000 cm−1. The calculated and experimental IR spectraIR spectrum of the synthesized calcium (II) and magnesiumMagnesium (II) complexes with glutamic acid were compared in order to validate their structures. Data on the coordination of calcium and magnesiumMagnesium ion complexes with amino acids contributes to understanding the structure of these poorly studied complexes and improving methods for obtaining these complex compounds with a predetermined composition and structure.