Search Results (11)

Despite a long period of application of metal implants, carbon–carbon medical composites are also widely used for bone defect prosthesis in surgery, dentistry, and oncology. Such implants might demonstrate excellent mechanical properties, but their biocompatibility and integration efficiency into the host should be improved. As a method of enhancing, the electrophoretic deposition of fine-dispersed hydroxyapatite (HAp) on porous carbon substrates might be recommended. With electron microscopy, energy dispersion X-ray and Raman spectroscopy, and X-ray diffraction, we found that the deposition and subsequent heat post-treatment (up to the temperature of 400 °C for 1 h) did not lead to any significant phase and chemical transformations of raw non-stoichometric HAp. The Ca/P ratio was ≈1.51 in the coatings. Their non-toxicity, cyto- and biocompatibility were confirmed by in vitro and in vivo studies and no adverse reactions and side effects had been detected in the test. The proposed coating and subsequent heat treatment procedures provided improved biological responses in terms of resorption and biocompatibility had been confirmed by histological, magnetic resonance and X-ray tomographic ex vivo studies on the resected implant-containing biopsy samples from the BDF1 mouse model. The obtained results are expected to be useful for modern medical material science and clinical applications. Full article

The rate of resorption of calcium phosphate self-hardening materials for bone regeneration can be changed by changing the phase composition. The Ca₃(PO₄)₂/CaCO₃/Ca(H₂PO₄)₂·H₂O/Na₂HPO₄·12H₂O system is important for the synthesis of self-curing bioactive materials with variable resorption rates by changing the ratios of the initial components. Cement compositions in twelve figurative points of a four-component composition diagram at a fixed content in the α-Ca₃(PO₄)₂ system were studied with XRD, FTIR, SEM, calorimetric, and volumetric methods to obtain an idea of the effect of composition on solubility in vitro and resorption in vivo. It was found that the presence of the highly resorbable phase of dicalcium phosphate dihydrate in cement and the substitution of phosphate ions with the carbonate ions of hydroxyapatite increased solubility in vitro and resorption in vivo. The obtained results confirm the possibility of changing the solubility of a final product in the Ca₃(PO₄)₂/CaCO₃/Ca(H₂PO₄)₂·H₂O/Na₂HPO₄·12H₂O system by changing the ratio of the initial components. Full article

Interest in calcium phosphate cements as materials for the restoration and treatment of bone tissue defects is still high. Despite commercialization and use in the clinic, the calcium phosphate cements have great potential for development. Existing approaches to the production of calcium phosphate cements as drugs are analyzed. A description of the pathogenesis of the main diseases of bone tissue (trauma, osteomyelitis, osteoporosis and tumor) and effective common treatment strategies are presented in the review. An analysis of the modern understanding of the complex action of the cement matrix and the additives and drugs distributed in it in relation to the successful treatment of bone defects is given. The mechanisms of biological action of functional substances determine the effectiveness of use in certain clinical cases. An important direction of using calcium phosphate cements as a carrier of functional substances is the volumetric incorporation of anti-inflammatory, antitumor, antiresorptive and osteogenic functional substances. The main functionalization requirement for carrier materials is prolonged elution. Various release factors related to the matrix, functional substances and elution conditions are considered in the work. It is shown that cements are a complex system. Changing one of the many initial parameters in a wide range changes the final characteristics of the matrix and, accordingly, the kinetics. The main approaches to the effective functionalization of calcium phosphate cements are considered in the review. Full article

Ceramic materials in Na₂O-CaO-P₂O₅ system were obtained by firing cement-salt stone made from pastes based on powder mixtures including calcium citrate tetrahydrate Ca₃(C₆H₅O₇)₂∙4H₂O, monocalcium phosphate monohydrate (MCPM) Ca(H₂PO₄)₂∙H₂O and/or sodium dihydrogen phosphate NaH₂PO₄. The phase composition of the obtained samples of cement-salt stone after adding water, hardening and drying included brushite CaHPO₄∙2H₂O, monetite CaHPO₄ and also unreacted Ca₃(C₆H₅O₇)₂∙4H₂O, Ca(H₂PO₄)₂∙H₂O and/or NaH₂PO₄. The phase composition of ceramics in Na₂O-CaO-P₂O₅ system obtained by firing cement-salt stone was formed due to thermal conversion of hydrated salt and heterophase reactions between components presented in samples during firing. The phase composition of ceramic samples based on powder mixture of Ca₃(C₆H₅O₇)₂∙4H₂O and Ca(H₂PO₄)₂∙H₂O after firing at 900 °C included β-calcium pyrophosphate (CPP) β-Ca₂P₂O₇. The phase composition of ceramic samples based on powder mixture of Ca₃(C₆H₅O₇)₂∙4H₂O, and NaH₂PO₄ after firing at 900 °C included β-sodium rhenanite β-CaNaPO_4. The phase composition of ceramic samples based on powder mixture of Ca₃(C₆H₅O₇)₂∙4H₂O, Ca(H₂PO₄)₂∙H₂O and NaH₂PO₄ after firing at 900 °C included β-Ca₂P₂O₇, β-CaNaPO_4, double calcium-sodium pyrophosphate Na₂CaP₂O₇, and Na-substituted tricalcium phosphate Сa₁₀Na(PO₄)₇. Obtained ceramic materials in Na₂O-CaO-P₂O₅ system including biocompatible and biodegradable phases could be important for treatments of bone tissue defects by means of approaches of regenerative medicine. Full article

Low-temperature ceramics based on magnesium calcium phosphate cement are a promising resorbable material for bone tissue restoration with the possibility of functionalization. The replacement of the magnesium Mg²⁺ ion with a calcium Ca²⁺ ion at the stage of preparation of the precursor leads to the production of multiphase ceramics containing phases of brushite, monetite, and newberyite, with different dissolution rates. Multiphase ceramics leads to volumetric resorption with preservation of their geometric shape, which was confirmed by the results of an evaluation of the output of magnesium Mg²⁺ and calcium Ca²⁺ ions into the contact solution of the ceramics and the X-ray density of ceramic samples during subcutaneous implantation. The combined introduction of sodium pyrophosphate decahydrate and citric acid monohydrate as setting inhibitors neutralizes their insignificant negative effect on the physico-chemical properties of ceramics (strength, pH, porosity), determining the optimal composition. In vivo experiments with setting inhibitors in the composition of ceramics showed a different biological response, affecting the rate of resorption on par with magnesium ions. Preliminary data on biocompatibility and solubility determined magnesium-calcium phosphate ceramics containing additives that regulate setting to be a potential material for bone tissue restoration and a vector for further research, including in orthotopic implantation models. Full article

Ceramics based on rhenanite CaNaPO₄ with density of 0.94 g/cm³ and compressive strength of 10.3 MPa was obtained via firing at 900 °C of composite cement-salt stone prepared from a hardening powder mixture of calcium citrate tetrahydrate Ca₃(C₆H₅O₇)₂∙4H₂O and sodium dihydrogen phosphate NaH₂PO₄. The phase composition of the obtained samples of cement–salt stone was represented by monetite CaHPO₄, unreacted sodium dihydrogen phosphate and calcium citrate tetrahydrate. According to the XRD data, the phase composition of the ceramic samples after annealing in the temperature range of 500–700 °C was mainly represented by the β-CaNaPO₄ phase. It was found that after an annealing at temperature of 900 °C, the phase composition of ceramics was presented with the only phase of β-CaNaPO₄. It was demonstrated that an increase in the annealing temperature led to an increase in the grain size from 1 μm after annealing at 500 °C to 5 μm after annealing at 900 °C. Obtained ceramic material based on CaNaPO₄ could be important for regenerative treatments of bone tissue defects. Full article

Rationale. Therapy with oral anticoagulants (OACs) in patients with atrial fibrillation (AF) is based on finding the optimal balance of efficacy and safety of these drugs. Data from observational studies are an additional source of information for the adverse events (AEs) of pharmacotherapy. Objective: To investigate pharmacotherapy AEs with OACs in the “ANTEY” prospective observational study in patients with non-valvular atrial fibrillation (AF). Material and Methods: A total of 201 people were enrolled (83 (41.3%) were women). The age of subjects was 71.1 ± 8.7 years (data presented as mean with standard deviation). The study protocol included two face-to-face visits (contacts V0 and V1) and one follow-up (FU) phone contact which were made with the patient at an interval of 6 months. At V0, all patients were recommended to take one of the non-vitamin K antagonist oral anticoagulants (NOACs); starting from V1, warfarin could have been prescribed or NOAC could have been changed. Information about AEs and OACsadministration was collected at V0, V1, and FU. Results. During 1 year of observation, 15 out of 201 patients refused to take OACs, and 186 initiated the recommended drug. Rivaroxaban was initiated in 93 patients, dabigatran in 46, apixaban in 40, and warfarin in 7 patients. There were 55 AEs, 25 of which were serious (SAEs), including 4 deaths. Of the 30 AEs, there were 18 bleedings: eight (8.6%) occurred with the administration of rivaroxaban; four (8.5%) with dabigatran, three (7.5%) with apixaban, and three (42.9%) with warfarin. Differences in the incidence of bleeding events between NOACs and warfarin are statistically significant (p = 0.025). Any AEs increased the chance of nonadherence to treatment nine-fold: OR = 9.2 (CI95%: 3.6–23.5), p < 0.0001. Conclusions. The most typical and common AEs in real-world clinical practice settings treatment with OACs were bleedings, the incidence of which was approximately 8% to 9% in the treatment with NOACs and was much higher with warfarin, bleedings in the treatment with OACs are statistically significantly associated with nonadherence to the use of these drugs in the future. Full article

Preceramic samples were prepared from pastes based on the aqueous solution of sodium silicate and tricalcium phosphate with a given molar ratio of (Na₂O · 2,87SiO₂)_aq/Ca₃(PO₄)₂ = 1:3 after drying at 24 °C and then 60 °C for 24 h. It established the dependence of the plastic strength of these pastes on both time and temperature and the possibility of using them for extrusion 3D printing. The phase composition of ceramic was represented by unreacted β-TCP (β-Ca₃(PO₄)₂) and β-rhenanite (β-NaCaPO₄) after heat treatment at 500 °C. Further, an increase in temperature up to 700 °C led to the appearing phase of silicon dioxide (SiO₂) and up to 900 °C, of sodium calcium phosphate (Na₃Ca₆(PO₄)₅). After heat-treatment at 1100 °C, ceramic samples consisted of the β-TCP (β-Ca₃(PO₄)₂), sodium calcium phosphate (Na₃Ca₆(PO₄)₅), silicon dioxide (SiO₂) and β-wollastonite (β-CaSiO₃). The bending and compressive strength of the ceramics rose with increasing temperature from ≈6.8 MPa and ≈31.1 MPa at 500 °C to ≈10.6 MPa and ≈43.5 MPa at 1100 °C. The obtained composite ceramics consisted of biocompatible phases that are widely studied in the literature and may be used as a biomaterial for the treatment of bone tissue defects. Full article

Biocompatibility of ceramic materials in Ca₂P₂O₇-Ca(PO₃)₂ system was investigated using different methods, including in vitro and in vivo tests. Ceramic materials in the Ca₂P₂O₇-Ca(PO₃)₂ system were obtained by annealing cement-salt stone based on powder mixtures of calcium citrate tet-rahydrate Ca₃(C₆H₅O₇)₂·4H₂O and monocalcium phosphate monohydrate (MCPM) Ca(H₂PO₄)₂·H₂O. The phase composition of cement-salt stone included brushite, monetite as a result of chemical reaction of starting components after adding of water. The presence of citric acid as by-product of chemical reaction, leads to increase the setting time of the cement-salt stone. Highly concentrated aqueous suspensions based on calcium citrate and MCPM powders providing content of calcium polyphosphate Ca(PO₃)₂ up to 20 wt % in ceramics were used for designing bioresorbable materials. The presence of an excess of monocalcium phosphate monohydrate makes it possible to reduce the annealing temperature of ceramics, which is associated with the formation of a lower melting phase of Ca(PO₃)₂. In vivo tests shown that obtained ceramic materials can be recommended for regenerative treatments for bone defects. Full article

Ceramic samples based on β-calcium pyrophosphate β-Ca₂P₂O₇ were prepared from powders of γ-calcium pyrophosphate γ-Ca₂P₂O₇ with preset molar ratios Ca/P = 1, 0.975 and 0.95 using firing at 900, 1000, and 1100 °C. Calcium lactate pentahydrate Ca(C₃H₅O₃)₂⋅5H₂O and monocalcium phosphate monohydrate Ca(H₂PO₄)₂⋅H₂O were treated in an aqua medium in mechanical activation conditions to prepare powder mixtures with preset molar ratios Ca/P containing calcium hydrophosphates with Ca/P = 1 (precursors of calcium pyrophosphate Ca₂P₂O₇). These powder mixtures containing calcium hydrophosphates with Ca/P = 1 and non-reacted starting salts were heat-treated at 600 °C after drying and disaggregation in acetone. Phase composition of all powder mixtures after heat treatment at 600 °C was presented by γ-calcium pyrophosphate γ-Ca₂P₂O₇ according to the XRD data. The addition of more excess of monocalcium phosphate monohydrate Ca(H₂PO₄)₂·H₂O (with appropriate molar ratio of Ca/P = 1) to the mixture of starting components resulted in lower dimensions of γ-calcium pyrophosphate (γ-Ca₂P₂O₇) individual particles. The grain size of ceramics increased both with the growth in firing temperature and with decreasing molar ratio Ca/P of powder mixtures. Calcium polyphosphate (t _melt = 984 °C), formed from monocalcium phosphate monohydrate Ca(H₂PO₄)₂⋅H₂O, acted similar to a liquid phase sintering additive. It was confirmed by tests in vitro that prepared ceramic materials with preset molar ratios Ca/P = 1, 0.975, and 0.95 and phase composition presented by β-calcium pyrophosphate β-Ca₂P₂O₇ were biocompatible and could maintain bone cells proliferation. Full article

New water-soluble polynorbornenes P1–P4 containing oligoether, amino acid groups and luminophoric complexes of iridium(III) were synthesized by ring-opening metathesis polymerization. The polymeric products in organic solvents and in water demonstrate intense photoluminescence in the red spectral region. The polymers P1 and P3 with 1-phenylisoquinoline cyclometalating ligands in iridium fragments reveal 4–6 fold higher emission quantum yields in solutions than those of P2 and P4 that contain iridium complexes with 1-(thien-2-yl)isoquinoline cyclometalating ligands. The emission parameters of P1–P4 in degassed solutions essentially differ from those in the aerated solutions showing oxygen-dependent quenching of phosphorescence. Biological testing of P1 and P3 demonstrates that the polymers do not penetrate into live cultured cancer cells and normal skin fibroblasts and do not possess cytotoxicity within the concentrations and time ranges reasonable for biological studies. In vivo, the polymers display longer phosphorescence lifetimes in mouse tumors than in muscle, as measured using phosphorescence lifetime imaging (PLIM), which correlates with tumor hypoxia. Therefore, preliminary evaluation of the synthesized polymers shows their suitability for noninvasive in vivo assessments of oxygen levels in biological tissues. Full article