[3H]Hyaluronic acid with a molecular weight of 2.37 MDa and a specific radioactivity of 35 GBq/g was obtained using the tritium thermal activation method. Tritium labeled hyaluronic acid (HA) with a molecular weight of 2.37, 0.20, and 0.10 MDa were used to study their adsorption on hydroxyapatite (HAP) in two textural modifications: aqueous suspension and powder. Differences in adsorption kinetics and adsorption isotherms were observed due to variations in the interaction between polysaccharide molecules and the sorbent forms under consideration. The adsorption isotherms of HA on HAP were proven linear. It is shown that strong HA–HAP complexes are formed, and no desorption of HA into water and 0.9

The influence of small amounts of ruthenium(iii) ions on the morphology, phase composition, and structure of the products formed under the conditions of hydroxyapatite (HAP) synthesis was studied by electron microscopy (including high resolution), energy dispersive analysis, and XRD. The introduction of doping ruthenium(iii) ions into the reaction medium at various stages of HAP formation affects the degree of aggregation of primary HAP—Ru nanoparticles. In the case of introducing Ru at the final stage of HAP synthesis, the formation of individual thread-like HAP—Ru nanoparticles is observed, but no formation of the intrinsic ruthenium phase is observed. The RuIII ions are distributed predominantly uniformly over the nanoparticle surface. The cocrystallization method for preparing composites of HAP with ruthenium radionuclides is promising for the development of new radiopharmaceuticals.

Composite materials based on gels and hydroxyapatite could provide promising characteristics for biomedical materials because of biocompatibility, osteointegration, and easy implementation. In this research, enzymatic synthesis of hydroxyapatite was studied as a technique for tissue engineering and scaffolds creation. The hydroxyapatite crystals were synthesized using this method and characterized with X-ray diffraction, electron microscopy, IR and Raman spectroscopy and analytical methods. As a result, a material with assumed composition of Ca10−x(HPO4)x(PO4)6−x(OH)2−x/CaHPO4/CaCO3 was obtained by enzymatic synthesis. The dynamics of size evolution, texture and crystallinity of the solid phase as a function of deposition time were also investigated. Afterwards, this method was used for gel mineralization with hydrogels such as agarose, alginate, gelatin, and polyacrylamide. Hydroxyapatite crystals obtained inside and above the hydrogels were analyzed with X-ray diffraction and electron microscopy. The particle diameter distribution functions were used to evaluate the mineralization in different gels. The shape and size of mineral inclusions depend on the density of the hydrogel grid. The localization of the formed solid phase depends on the nature of the gel and the concentration of alkaline phosphatase inside it. The results provide an opportunity to control the morphology of calcium phosphate particles produced during mineralization, which is important for the creation of biomedical materials with specified and reproducible characteristics.

The parameters of the sorption of yttrium ions on hydroxyapatite samples of various textural organization, viz. , lamellar nanoparticles (HAP n ) and porous microparticles synthesized by the enzymatic method (HAP e ), were studied. The values of the maximum amount adsorbed are shown to be higher in the case of HAP e , while the sorption process is faster in the case of HAP n . The sorption kinetics is well described by a pseudo-second-order model. The kinetics of isotope exchange between sorbed and dissolved yttrium was studied by the method of radioactive indicators using the 90 Y label. The exchange proceeds in several stages, at the first of which the available yttrium is exchanged from the sorbent surface. In the case of HAP e , a slow stage of yttrium exchange is observed apparently related to the yttrium located in the pore space of microparticles.

The sorption kinetics of zinc ions and bovine serum albumin (BSA) on the surface of suspended hydroxyapatite (HAP) was studied. The sorption kinetics of zinc ions and BSA is described by the pseudo-second-order Lagergren equation. The maximum amounts of both components adsorbed in the course of the sequential and parallel sorption of BSA and zinc ions on HAP are lower than those found for sorption of the individual components on HAP. The interaction of zinc ions with BSA in a solution results in the formation of particles composed of complexes, the average size of which increases with increasing concentration of metal ions until some particles reach the size needed for the isolation of a separate solid phase.

A significant difference in behavior of ZrIV ions during their cocrystallization and sorption binding to hydroxyapatite (HAP) is demonstrated. When the concentration of doping ions exceeds 10−4 mol L−1, a chemical reaction with the formation of amorphous zirconium phosphate and complete dissolution of the sorbent occurs in the system rather than sorption. According to the X-ray diffraction and transmission electron microscopy (TEM) data, a similar reaction is also possible at lower concentrations of zirconium ions. The effect of doping ions on the morphology and structure of HAP is significantly lower for the cocrystallization introduction of Zr. In addition, according to high-resolution TEM data, doping ions can uniformly be distributed over the carrier surface or volume. Therefore, this method of binding method can be recommended for the preparation of a target HAP-Zr complex.

A cell for studying the diffusion of therapeutic medical radionuclides into the macrolayer of the carrier sorbent was fabricated using 3D printing. The diffusion of ultramicroquantities of radium and strontium within a layer of watered hydroxyapatite was investigated. The value of the effective diffusion coefficient obtained using a one-dimensional nonstationary model was (1.0 ± 0.4) × 10 –8 cm 2 /s for Ra and (3.0 ± 0.3) × 10 –8 cm 2 /s for Sr.

In order to characterize hydroxyapatite (HAP) as a possible carrier of medicinal drugs and radionuclides, the possibility of using HAP modified with zinc ions (HAP-Zn) for the sorption of albumin, in particular, bovine serum albumin (BSA), was considered, using the latter as an intermediate binding protein in complex with a heterocyclic ligand of medical purpose. The kinetics of sorption of albumin correspond to the pseudo-second order, and the parameters of the sorption isotherm can be described using calculations based on the Langmuir theory of monolayer adsorption. The results of experiments on the sequential and joint sorption of a heterocyclic ligand on HAP-Zn in the presence of BSA are ambiguous about the sorption binding of this ligand to the sorbent, however, an interaction (binding) between the starting BSA and the ligand was present.

Using a 36Cl radioactive label, we study the behavior of chloride ions during the adsorption interaction of hydroxyapatite (HA) with an aqueous solution of magnesium chloride at high concentrations. The kinetics of transfer of the label from the solution to the solid phase is investigated by liquid scintillation spectrometry, and the boundary concentrations of magnesium chloride at which this effect manifests itself are determined. At a concentration of the chloride ions above 0.6 mol/L, a topochemical reaction may occur with the incorporation of Cl– into the hydroxyapatite structure and the formation of an extraneous phase (whitlockite) or mixed Ca–Mg apatites with the partial replacement of OH by Cl.

Sorption of zinc ions and 69mZn radionuclide proceeds much more rapidly on hydroxyapatite modified with zinc ions (HAP-Zn) than on unmodified HAP. The sorption can be described by a pseudo-second order model and probably follows an exchange mechanism, as evidenced by the transfer of calcium ions into the mother liquor during the process. Sorbed 69mZn participates in a slow reverse isotope exchange with the solution containing non-radioactive zinc ions.

The sorption behavior of 89Zr on hydroxyapatite (Ca10(PO4)5(OH)2, HA) nanoparticles in an aqueous medium and 0.9% NaCl at various pH values was studied. The fast kinetics of the process was determined; the stability of the obtained conjugate in a model biological medium at 25 and 37 °C was shown. The possibility of further use of the 89Zr@HA conjugate in various radiopharmaceuticals is discussed.

The sorption of the actinium(iii) ions as 225,228Ac isotopes on hydroxyapatite (HAP) with various textures was studied. A “reverse” generator using an extraction chromatographic sorbent based on diglycolamide derivative (DGA Resin) was proposed for 228Ac production. The chemical yield of the product was ≥90%. The optimal acidity of the solution during sorption (pH 6–7) and the ratio of solid and liquid phases (20 mg of the sorbent per mL of the solution) were determined in preliminary experiments. The process kinetics is adequately described by pseudo-second-order model. The stationary state is reached rapidly (in 10 min) when a HAP suspension is used, whereas time (20–30 min) is needed for textured samples. The possibility of actinium ion diffusion within the bulk of these samples is shown. The diffusion coefficient of actinium estimated by diffusion in a wet HAP paste layer (one-dimensional model) was (1.0±0.2) • 10−7 cm2 s−1.

Specific features of the interaction between bismuth(iii) and hydroxyapatite (HAP) of various morphologies during its sorption and co-crystallization binding were revealed. The obtained sorption isotherms nearly coincide with each other regardless of the HAP type used and cannot be described in terms of the Langmuir or Freundlich models. Bismuth can form the intrinsic phase of bismuth phosphate due to the chemical or topochemical reaction with HAP when the sorption method is used. In the case of co-crystallization binding of bismuth ions, the morphological modification of HAP occurs. The bismuth complexes with aminopyrimidine in neutral and weakly acidic solutions are readily hydrolyzed to form a precipitate, and no binding with HAP occurs.

We have studied Mg2+ adsorption on hydroxyapatite (HAp) nanocrystals and constructed its isotherm at equilibrium cation concentrations in the range 0–0.35 mol/L. For a number of samples, corresponding to characteristic points in the adsorption isotherm, the composition and the oxidation state of the elements present on the surface of the sorbent have been determined by X-ray photoelectron spectroscopy (XPS). The surface magnesium concentration determined by XPS, which detects only ions in a surface layer a few nanometers in thickness, has been found to be considerably lower than the total amount of cations in the solid phase, evaluated from the experimentally determined adsorption isotherm. We assume that, during the sorption process, some of the magnesium ions substitute for calcium ions in the bulk of the HAp and some adsorb in the form of MgCl2. The results obtained in this study constitute a fundamental basis for practical solutions in designing integrated medications based on HAp with magnesium.

Dispersions based on sodium hyaluronate and hydroxyapatite, which is synthesized both by the classical method in an aqueous medium to obtain submicron particles and in a bioactive hyaluronan medium with the formation of nanosized particles, are obtained. The synthesized hydroxyapatite nanoparticles have a complex structure based on a monodentate complex hyaluronan–Ca 2+ which remains in the dispersion both when adding a hyaluronan solution and when diluted with water. Physicochemical methods show that there is a significant difference between the energy characteristics of the surfaces of biocomposites obtained from dispersions. The rheology of dispersions of hydroxyapatite micro- and nanoparticles is investigated, the effect of dispersed phase concentration on it is revealed, and the viscoplastic behavior of dispersions of microparticles is demonstrated. This behavior disappears upon addition of the hyaluronan solution, which, however, leads to the loss of stability by the system. The introduction of hydroxyapatite nanoparticle additives into hyaluronan solutions has a weak effect on the rheology; no flocculation of nanoparticles occurs. The resulting composites consisting of hydroxyapatite and sodium hyaluronate can be considered a basis of a drug for the rehabilitation treatment of periodontitis.