O. A. Golovanova

Specific features of pathogenic mineral formation in the human body

Key relationships in pathogenic mineral formation within the human body were summarized. It was shown that pathogenic organomineral aggregates in human body are formed in complex multicomponent media containing organic and inorganic components. In the course of lithogenesis, the composition of biological fluid undergoes major changes. Phase formation in human urine and oral fluid in the initial stages leads to emergence of less thermodynamically stable phases, i.e., is kinetically controlled. Amino acids, as well as a number of inorganic impurities, are actively involved in crystallization of the main phases of renal calculi.

Main features of nucleation in model solutions of oral cavity

The regularities of nucleation in model solutions of oral cavity have been investigated, and the induction order and constants have been determined for two systems: saliva and dental plaque fluid (DPF). It is shown that an increase in the initial supersaturation leads to a transition from the heterogeneous nucleation of crystallites to a homogeneous one. Some additives are found to enhance nucleation: HCO3− > C6H12O6 > F−, while others hinder this process: protein (casein) > Mg2+. It is established that crystallization in DPF occurs more rapidly and the DPF composition is favorable for the growth of small (52.6–26.1 μm) crystallites. On the contrary, the conditions implemented in the model saliva solution facilitate the formation of larger (198.4-41.8 μm) crystals.

Crystallization of calcium oxalate monohydrate in the presence of amino acids: Features and regularities

The protein composition of the organic component of kidney stones and the effect of major amino acids of the physiological solution on the crystallization process of calcium oxalate is studied in the work. By means of a complex technique the protein compounds are analyzed in 40 samples of kidney stones obtained by both direct surgical operations and distant lithotripsy. A strong and selective concentration of amino acids in different stones in comparison with the physiological fluids forming them is established. Nucleation processes and the crystallization kinetics of calcium oxalate monohydrate are studied in the model solutions without impurities and with additions of 13 amino acids. Different amino acids can both inhibit and promote these processes depending on the acid structure.

To the formation of aggregate structures of kidney stones

The work considers the aggregation process of calcium oxalate monohydrate crystals (whewellite) during their crystallization from aqueous solutions. The intensive crystal aggregation during the precipitation is evidenced by a decrease in the bulk concentration against an increase in the crystal size. At the initial stages of crystallization fine particles are mainly captured by larger ones in the form of substance deposition on the initiating centers: organic blobs, dead cells, and so on. During the crystallization the effect of the dominant growth of large aggregates increases; the process develops autocatalytically; fine particles disappear more rapidly than large ones, and the crystal size distribution compresses simultaneously with an increase in the average particle size.

Main features of nucleation in model solutions of blood plasma

The regularities of nucleation in a model solution of human blood plasma under the conditions similar to physiological have been investigated. The induction order and constants are determined. It is shown that an increase in supersaturation leads to a transition from heterogeneous to homogeneous nucleation of crystallites. The critical nucleus size is estimated for a pure model system and for a system containing a number of additives. The impurities under study are found to form the following descending sequence with respect to their effect on nucleation: alanine > glucose > glycine > citric acid > milky acid > magnesium ions.

Kinetic characteristics of the crystallization from model solutions of blood plasma

The kinetic regularities of crystallization (growth order and constants) in a model solution of blood plasma have been investigated. The particular order and crystallization constant are determined to be n < 1 and k = 12.30–26.91 moln L–n s–n, respectively. The impurities are found to form the following descending sequence with respect to their inf luence on the particular kinetic characteristics of crystallization: milky acid > magnesium ions > alanine, glycine, glucose, and citric acid. It is shown that the impurities affect to a greater extent the nucleation rather than the growth stage. It is also established that a change in рН within 7.0–8.0 does not affect the crystallization parameters of the system modeling the composition of human blood plasma.

Crystallization specifics of carbonate-hydroxylapatite in the presence of strontium-containing agents

The effect of strontium-containing compounds on the crystallization of strontium-substituted carbonate- hydroxylapatite from a human synovial fluid prototype was studied. Synthesis products were investigated by FT-IR spectroscopy, X-ray diffraction, and differential thermal analysis. The amount of strontium in samples was determined by atomic emission analysis. For the synthesized phases, crystallite sizes were calculated by the Selyakov–Sherer formula, and the unit cell parameters were determined. The kinetically stable brushite phase was shown to transform into the more thermodynamically stable phase of strontium-containing carbonate-hydroxylapatite with increasing exposure time of precipitates under the mother solution. Some schemes were proposed for phase transformations under heat treatment.

Crystallization of carbonate hydroxyapatite in the presence of strontium ranelate

The influence of strontium ranelate on the crystallization of carbonate hydroxyapatite from a prototype of synovial fluid of humans has been investigated. The synthesis products are studied by IR Fourier spectroscopy, X-ray diffraction, and differential thermal analysis. The amount of strontium in the samples is determined by atomic emission analysis. The sizes of crystallites in the synthesized phases are calculated from the Selyakov–Scherrer formula; the lattice parameters are also determined. The phases obtained are found to be species of calcium-deficient strontium-containing carbonate hydroxyapatite of mixed A and B types. Schemes of chemical reactions occurring during heat treatment are proposed.

Patterns of calcium oxalate monohydrate crystallization in complex biological systems

The paper presents the features of calcium oxalate crystallization in the presence of additives revealed through experimental modeling. The patterns of phase formation are shown for the Ca2+ – C2O4 2– – H2O and Ca2+ – C2O4 2– – PO4 3– – H2O systems with the components and pH of the saline varying over a wide concentrations range. The effect of additives on crystallization of calcium oxalate monohydrate was investigated. It was found that the ionic strength and magnesium ions are inhibitors, and calcium oxalate and hydroxyapatite crystals are catalysts of calcium oxalate monohydrate crystallization. The basic calcium phosphate (apatite) was found to be most thermodynamically stable, which indicates its special role in kidney stone formation since it is found in virtually all stones.

Thermodynamics and kinetics of calcium oxalate crystallization in the presence of amino acids

Specific features of the crystallization of calcium oxalates (CaC2O4) in the presence of amino acids have been established based on thermodynamic and experimental modeling. Phase formation in the Ca2+–C2O42-–H2O–amino acid system in a wide range of variation in the component concentrations and solution pH have been theoretically investigated. The influence of pH on the thermodynamic stability of crystallizing compounds is considered. The effect of amino acids of different structures on the formation of the CaC2O4 solid phase in a prototype of physiological solution is analyzed. The kinetic crystallization parameters (induction period and rate constant) and crystallite growth are determined.