[Show abstract][Hide abstract] ABSTRACT: We have studied the structure of hydroxyapatite (HA) powders prepared by hydrolyzing dicalcium phosphate dihydrate (DCPD) in an aqueous sodium acetate solution at a temperature of 60°C for 16 h or a longer time. The results demonstrate that the HA in the powders has a distorted structure. The Baur’s distortion index for the PO4 tetrahedra is DI(TO) ≃ 0.03, whereas hydroxyapatite single crystals have DI(TO) ≃ 0.005. The powders are similar in structural parameters to calcium-deficient HAs: they have Ca/P ≃ 1.6 and an imperfect substructure (crystallite size of ≃30 nm) and contain sodium impurities. The structural features of the HA powders are analyzed in the context of their ability to biodegrade (dissolve).
Full-text · Article · Feb 2016 · Inorganic Materials
[Show abstract][Hide abstract] ABSTRACT: The possibility of strengthening chitosan containing calcium phosphate bone cements sintered with tricalcium phosphate granules was studied. The strength was found to depend on the granules content in a nonmonotonic manner. For materials reinforced with 300–500 μm granules in the amount of 20 wt %, the compression strength of about 15 MPa was reached on day 14 of air hardening, which was 50 % higher than that of the unreinforced cement matrix. The main crystalline phase of the cement matrix is amorphous calcium phosphate. Dissolution of cement in isotonic saline corresponds to first order reaction kinetics.
Full-text · Article · Feb 2016 · Inorganic Materials: Applied Research
[Show abstract][Hide abstract] ABSTRACT: A creation of personalized constructions for tissue engineering of bone tissue is very perspective biomedical technological trend. An aim of our work was studying physicochemical characteristics, cyto-and biocompatibility of 3D printed constructions based on sodium alginate and three calcium phosphates species (tricalcium phosphates, carbonated hydroxyapatite, and octacalcium phosphate). The methods of 3D constructions producing included 3D printing of components with crosslinking agent (CaCl2), their freezing, sublimation, "forced shrinkage", γ-ray sterilization (15 kGr). A structure of 3D constructions, their porosity and strength characteristics were studied. The cytocompatibility of 3D constructions and matrix-for-cell properties were investigated in vivo on a model of human osteosarcoma MG-63 cell line by means of MTT assay. The biocompatibility of 3D constructions was studied on the model of subcutaneous implantation in mice up to 12 weeks. Using scanning electron microscopy it was found that all 3 types of constructions have a lamellar structure of alginate component with spherical inclusions of calcium phosphate. Total porosity of species was 54,5-63,9%. Calcium phosphates in the constructions reserved initial phase composition. Compressive strength of 3D constructions depended on inorganic component and was 1,8-3,7 MPa with ultimate strain 12,3-12,6%. All types of 3D constructions were cytocompatible in vitro, demonstrated good matrix-forcells properties, and had supported cell proliferation for 2 weeks. In results of subcataneous in vivo test all constructions demonstrated biocompatibility with slow bioresorption of organic and inorganic components. Received data proved the promising outlook for further improvement of 3D printing and investigations of described 3D constructions as osteoplastic materials.
[Show abstract][Hide abstract] ABSTRACT: In the paper formulation of the problem and describe the study of deposition of nanofilms on porous alumina substrate are shown. The equations of the modified embedded atom method are considered. These equations are the basis of many-particle interaction potential of atoms. Various elements of the Mendeleev periodic system are used as deposition materials. Various mechanisms overgrowth of a porous substrate of alumina are obtained. Recommendations for obtaining of nanofilms materials of different structures are formulated.
[Show abstract][Hide abstract] ABSTRACT: The mathematical model of condensation processes of metal nanoparticles from a gas phase is submitted. The determination method of mechanical, numerical and structural nanoparticles properties is proposed. Theoretical analysis of composites elastic characteristics including nanoparticles is carried out. Calculation results of metals nanoparticles formation at vacuum evaporation and condensation are given. Numerical and structural properties of forming nanoobjects are examined. Dependences of structural behavior for nanoobjects and composites on its basis are obtained.
[Show abstract][Hide abstract] ABSTRACT: A process for manufacture of chitosan-based biodegradable biopolymer membranes suitable for medical applications was developed. A technology for inclusion of broad spectrum antibiotics into the chitosan membranes was elaborated. The effects of pH of the solution surrounding the membranes and the initial solvent chosen for chitosan on the kinetics of release of antibiotics from the membranes were studied. It was demonstrated that the kinetics of drug release from the chitosan-based biodegradable biopolymer membranes depends on the properties of substance immobilized in the membrane, the membrane manufacture process, and extraction conditions.
Full-text · Article · Nov 2015 · Doklady Chemistry
[Show abstract][Hide abstract] ABSTRACT: General mathematical model of self-organization of nanostructures is presented. The results of computer simulation of nanostructure formation processes are listed. Different mechanisms formation of quantum dots on an oriented silicon surface are demonstrated.
[Show abstract][Hide abstract] ABSTRACT: The paper discusses the results of research vacuum, air and aerosol nanosystems. It was carried out modeling of condensation inside vacuum nanosystems for producing metal nanoparticles, which is realized by evaporation, the thermal saturation and the subsequent condensation of vapor on or near the cold surface. Methods of modeling and research of condensation processes of nano - objects in vacuum, air and aerosol media are describing. The methodology involves the calculation of the structural and quantitative properties of nanoparticles, ranging from the construction of the structure of molecules and finishing phase condensation already formed nanostructures.
[Show abstract][Hide abstract] ABSTRACT: A mathematical model obtaining special nanostructured layers in epitaxial structures for thin photoelectric converters (PEC) is presented. The results of computer simulation of the production of nanostructured objects in epitaxial structures for the refined PEC are given. The silicon atoms, gallium, indium and gold are considered as the initial forming elements. The results of test calculations are shown, which consider autocorrelation, radial functions and temperature graph. Different mechanisms of formation nanostructures in epitaxial structures for thin photoelectric converters are demonstrated.
[Show abstract][Hide abstract] ABSTRACT: The study presents results of development and investigation of processes of three-dimensional inkjet printing of scaffold structures based on microgranules of tricalcium phosphate and their further chemical modification in buffer solutions with the purpose of manufacturing bioactive ceramic scaffolds for bone tissue engineering.
[Show abstract][Hide abstract] ABSTRACT: Biocompatible calcium phosphate ceramic grafts are able of supporting new bone formation in appropriate environment. The major limitation of these materials usage for medical implants is the absence of accessible methods for their patient-specific fabrication. 3D printing methodology is an excellent approach to overcome the limitation supporting effective and fast fabrication of individual complex bone substitutes. Here we proposed a relatively simple route for 3D printing of octacalcium phosphates in complexly shaped structures by the combination of inkjet printing with post-treatment methodology. The printed octacalcium phosphate blocks were further implanted in the developed cranial bone defect followed by histological evaluation. The obtained result confirmed the potential of the developed octacalcium phosphates bone substitutes, which allowed 2.5-time reducing of defect’s diameter at 6.5 months in a region where native bone repair is extremely inefficient.
Full-text · Article · Jun 2015 · Frontiers in Bioengineering and Biotechnology
[Show abstract][Hide abstract] ABSTRACT: In this chapter, simulation method of structural, quantitative and deformation properties of nanoparticles and their composites are investigated. The present- ed model allows to study the dynamic characteristics nano-objects throughout the life cycle of their use, starting from the processes of formation of nanopar- ticles and ending its influence on the mechanical parameters of the composite.
[Show abstract][Hide abstract] ABSTRACT: Abstract Severe plastic deformations lead to structural transformations in dense microcrystalline hydroxyapatite (HA, Ca10(PO4)6(OH)2) ceramics and particularly to formation of nanocrystalline structure with tricalcium phosphate (α-TCP) and amorphous calcium phosphate (ACP) inclusions. In the present work we studied the substructure and hardness of ceramics using nanoindentation and transmission electron microscopy. Our results are in agreement with the cluster mechanism of the HA structure (Ca9(PO4)6, Ca3(PO4)2 and PO 4 3 − ) model representing deformation of HA by cluster fragmentation and cluster-boundary “sliding”.
No preview · Article · May 2015 · Ceramics International
[Show abstract][Hide abstract] ABSTRACT: We have studied the microstructure formation in composite cement materials consisting of amorphous calcium phosphate and chitosan and reinforced with sodium alginate granules, their compressive strength, and the kinetics of their dissolution in an isotonic solution. Hardening in air allowed us to obtain a cement stone with a strength of up to 18 MPa and limiting strain of 6–8%. During hardening in simulated body fluid, the maximum strength decreased to 0.8 MPa, and the strain increased to 25–30%, which was due to the dissolution of the granules and the increase in the elasticity of the chitosan framework. The calcium ion release to the isotonic solution varied nonmonotonically, with a maximum in the initial stage of hardening. The cements are intended for the fabrication of porous matrices in bone tissue regeneration.
No preview · Article · Apr 2015 · Inorganic Materials
[Show abstract][Hide abstract] ABSTRACT: Powders prepared through dicalcium phosphate dihydrate (DCPD) hydrolysis to octacalcium phosphate (OCP) and hydroxyapatite (HA) in an aqueous sodium acetate solution have been characterized by X-ray diffraction. The lattice parameters of the synthesized OCP and HA phases have been determined as functions of holding time at synthesis temperatures of 37 and 60°C. The structure of the HA obtained through hydrolysis at 60°C has been refined, and the distortion of the elements of the crystal lattice of this compound has been assessed in terms of Baur indices. A model has been proposed for the heterogeneous nucleation and growth of the OCP phase on DCPD crystals, in which the structure of these compounds is represented as made up of groups similar in structure to Posner regions.
No preview · Article · Apr 2015 · Inorganic Materials
[Show abstract][Hide abstract] ABSTRACT: A method for surface-selective laser sintering which produces mineral-polymeric materials based on calcium phosphates and aliphatic polyesters was developed. Three-dimensional matrices of the given architectonics for replacement of bone defects and bone tissue engineering were obtained. The microstructure of the experimental samples obtained and their surface morphology and internal structure were investigated by scanning electron microscopy (SEM). The characteristic values of the compressive strength and relative deformation of the mineral-polymer composite samples obtained by surface-selective laser sintering of fine powders consisting of 80 wt % ceramic granules based on tricalcium phosphate and 20 wt % D,L-polylactide PDL04 corresponded to the characteristic indices of the similar parameters for the trabecular bone tissue. As a result of the initial study of the biological properties of mineral-polymer composite scaffolds made by surface-selective laser sintering, it was shown that they had low cytotoxicity and no adverse effects on the proliferative potential of mesenchymal stem cells. The technology of surface-selective laser sintering suggested could be effectively used to create scaffolds for bone tissue engineering.
Full-text · Article · Mar 2015 · Inorganic Materials: Applied Research
[Show abstract][Hide abstract] ABSTRACT: В работе рассмотрены результаты исследований вакуумной, воздушной и
аэрозольной наносистем. Моделирование процессов конденсации внутри вакуумных
наносистем проводилось для метода производства металлических наночастиц, который
реализуется испарением, термическим насыщением и последующей конденсацией пара
вблизи холодной поверхности. Формирование наночастиц в воздушных средах
исследовалось для задачи внесения удобрений через поры растений в виде наночастиц
минеральных солей. Процессы конденсации в аэрозольных огнетушителях послужили
объектом исследования многокомпонентных гетерофазных наноаэрозольных систем.