Tetiana Kalinichenko - Academia.edu (original) (raw)

Papers by Tetiana Kalinichenko

Journal of Nano- and Electronic Physics, 2016

Crystal Research and Technology, 2013

ABSTRACT Complementary experimental techniques were applied to characterize bioapatite nanocrysta... more ABSTRACT Complementary experimental techniques were applied to characterize bioapatite nanocrystals from pathological cardiovascular deposits. The investigated collection included the leaflets from aortic valve, leaflets from mitral valve, leaflets from tricuspid valve and calcified aorta's wall. XRD, EDX and FTIR data have shown that all studied samples consist of imperfect apatite with different crystallinity and variable chemical composition. In accordance with TEM data, the crystals of pathological calcified deposits frequently have oblong or rod-like shape (length of 60-90 nanometers, width of 20-30 nanometers). At the same time, in the SEM and TEM experiments, the complex spheroid assemblies and planar sheet-like shaped formations with crystal structure close to apatite were observed. Probably, the different shape and morphology of the particles are caused by different ways of crystal nucleation and growth, although the exact mechanisms remain an open question.

Ceska a slovenska oftalmologie : casopis Ceske oftalmologicke spolecnosti a Slovenske oftalmologicke spolecnosti, 2014

The authors have described the case of pathological biomineralization of ocular posterior chamber... more The authors have described the case of pathological biomineralization of ocular posterior chamber. Histological examination of affected eye shells revealed inflammation, oedema, dyscirculatory violations, and signs of dystrophic calcification. Structural-phase and chemical analyses of calcification have revealed that the biomineral consists of hydroxyapatite with relatively small crystallite size and defective crystal lattice. In the described case the formation of pathological biomineral in the vision organ was initiated by penetrating wound. Eye injury might have caused a hemophthalmus and chronic inflammatory reaction in the shells, these processes eventually led to the organ subatrophy and to the development of dystrophic and necrobiotic changes in the tissues. Pathological biomineralization in the affected organ developed as a type of dystrophic calcification.Key words: eye, pathological biomineralization, hydroxyapatite.

Journal of Biomedical Materials Research Part A, 2011

Chitosan/hydroxyapatite scaffolds could be used for bone regeneration in case the application of ... more Chitosan/hydroxyapatite scaffolds could be used for bone regeneration in case the application of auto-or allografts is impossible. The objective of the present work was to characterize and study in vivo biodegradation of simple chitosan/hydroxyapatite scaffolds. For this purpose, a series of chitosan/hydroxyapatite composites has been synthesized in aqueous medium from chitosan solution and soluble precursor salts by a one step coprecipitation method. A study of in vivo behavior of the materials was then performed using model linear rats. Cylindrical-shaped rods made of the chitosan/hydroxyapatite composite material were implanted into tibial bones of the rats. After 5, 10, 15, and 24 days of implantation, histological and histo-morpho-metric analyses of decalcified specimens were performed to evaluate the stages of biodegradation processes. Calcified specimens were examined by scanning electron microscopy with X-ray microanalysis to compare elemental composition and morphological characteristics of the implant and the bone during integration. Porous chitosan/hydroxyapatite scaffolds have shown osteoconductive properties and have been replaced in the in vivo experiments by newly formed bone tissue. V C 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 96A: 639-647, 2011.

ORTHOPAEDICS, TRAUMATOLOGY and PROSTHETICS, 2009

ABSTRACT A number of chitosane/hydroxyl apatite composite materials were synthesized from aqueous... more ABSTRACT A number of chitosane/hydroxyl apatite composite materials were synthesized from aqueous solutions of a biopolymer and soluble salts-precursors. The composites were obtained in the dense and porous variants. The examinations conducted by the methods of X-ray diffraction analysis and infrared spectroscopy showed that apatite crystals in the composites had structural characteristics similar to those of biogenic apatite. Cylindrical rods, made of chitosane/hydroxyl apatite composite materials, were experimentally implanted into the tibial bone of linear laboratory rats in vivo. Histological and histomorphological studies for assessing osteoconductivity were performed 5, 10, 15 and 24 days after the implantation. The specimens were examined by the method of scanning electronic microscopy with X-ray microanalysis for comparing the elemental composition and morphological characteristics of the implant and bone during the integration. The results of the tests make it possible to conclude that chitosane/hydroxyl apatite composites are bioinert and biocompatible. The porous specimens also demonstrated satisfactory osteoconductive properties and were experimentally replaced in vivo by a newly formed bone tissue.

Crystal Research and Technology, 2010

ABSTRACT Composite biomaterials based on chitosan and calcium apatite with different chitosan/apa... more ABSTRACT Composite biomaterials based on chitosan and calcium apatite with different chitosan/apatite ratio were prepared by chemical synthesis of apatite in chitosan solution using one-step co-precipitation method. Initial and annealed samples were characterized by X-ray diffraction, FTIR spectroscopy and scanning electron microscopy coupled to energy-dispersive electron X-ray spectroscopy. The data obtained suggest that the formation of the calcium-phosphate mineral in chitosan solution is substantially modulated by the chemical interaction of the components; apparently, a part of calcium is captured by chitosan and does not participate in the formation of the main mineral phase. The apatite in the composite is calcium-deficient, carbonate-substituted and is composed of dispersed nano-sized crystallites, i.e. has properties that closely resemble those of bone mineral. Varying synthesis, drying and lyophilization conditions, the composite materials can be produced with the desirable chitosan/apatite ratio, both in the dense and porous form. The structural analysis of composite samples after annealing at certain temperatures is examined as an approach to elucidate the mechanism of co-precipitation by one-step method. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

(Получено 12.02.2016; в отредактированной форме – 02.03.2016; опубликована online 15.03.2016) В р... more (Получено 12.02.2016; в отредактированной форме – 02.03.2016; опубликована online 15.03.2016) В работе приведены результаты исследований морфологии, структуры, элементного и фазового со-става кальцинированных фрагментов патологических образований щитовидной железы. Методами рентгеновской дифракции и инфракрасной спектроскопии установлено, что все исследованные пато-логические кальцификаты представляет собой дефектный карбонатзамещенный апатит кальция Ca10(PO4)6(OH)2. Показано, что применение просвечивающей электронной микроскопии в комбинации с микродифракцией электронов позволяет выявить некоторые структурные и морфологические осо-бенности кристаллов апатита щитовидной железы, не обнаруживаемые другими методами. Благода-ря этому, при условии применения тонкого препарирования на стадии анатомических исследований и подготовки пробы, может быть реализован локальный морфологический и структурный анализ мине-ральных составляющих депозита как при одном и том же клиническом случае, так и при их широком разнообразии.

—The methodical aspects of preparation of biopolymer gels using cryotechniques have been consider... more —The methodical aspects of preparation of biopolymer gels using cryotechniques have been considered. By the example of swollen corn starch grains, it is shown that, using a cryostat in scanning electron microscopy, aqueous biopolymer gels can be investigated without artifacts if the sample temperature lies in the range 130–140°C. In many areas of production, biotechnology is based on the translation of biopolymers into the gel state. A biopolymer gel is a spatial network (framework) with structural elements relatively rigidly connected with each other; each structural element can undergo reversible deformation upon bending or extension. The morphology of polymer gels is fairly complex, since twophase (nonequilibrium) systems are characterized by the formation of a number of intermediate states. In gelforming systems, layering is never completed and their morphology is a mixture of the primary structure and the structure formed as a result of partial fracture of the matrix phase [1]. In the modern stage of development of new materials with specific properties, the role of electron microscopy continuously increases. This method became a routine tool for monitoring the structure of various materials, especially in the nanotechnology research [2–4]. In the use of the methods of electron microscopy, it is necessary to take into account that the exact quantitative analytical methods that are used in modern instruments are limited by the uncertainties related to the sample preparation for analysis. It should be noted that ambiguous results were obtained in the studies devoted to the methods for preparing biopolymer gels, and the conclusions drawn contradict the data of other studies [5, 6]. The most widespread methods for preparing biopolymer gels are as follows: negative staining, freeze–etching, and freeze–fracture for transmission electron microscopy (TEM) and freeze–drying for scanning electron microscopy (SEM). Ultramicrotomy, cryomicrotomy, and critical point drying are more rarely used. In this study, we analyzed the possibilities of the following cryotechniques for biopolymer gel preparation: freeze–drying, freeze–fracture, and investigation in a cryostat. As an object of study, we chose swollen corn starch grains. Starch and starch-containing raw materials are widely used in food industry as gelling agents, foam and emulsion thickeners, and other nonfood materials. The experiment was performed using SEM (S-2500, Hitachi) and TEM (EM-125, Sumy, Ukraine). In addition, a REM-100U scanning electron microscope with a RUPIK cryostat (Sumy, Ukraine) was applied. Using RUPIK and the cryomicrotome built-in in the microscope, one can perform layer-by-layer analysis of a frozen sample at low temperatures that are used in cryotechniques: from –100 to – 140°C. The RUPIK design features make it possible to investigate the same portion of a sample by SEM and TEM, since a carbon–platinum replica can be deposited on the sample surface by laser sputtering of the material directly in the electron microscope; such a procedure excludes sample heating during its preparation. To determine the sample freezing rate, we used an ISK indicator, which allows thermographic detection of small ice crystals when cryotechniques are used. It is known

Journal of Applied Spectroscopy, 2006

We have attempted to use heat treatment followed by ultrasonic treatment to separate the apatite ... more We have attempted to use heat treatment followed by ultrasonic treatment to separate the apatite from the non-apatite components of bone mineral in samples from different animals. The Mg content and the Ca/P ratio in the temperature range 560 o C-720 o C in the samples before and after ultrasonic treatment were determined by electron-probe x-ray microanalysis. Furthermore, we used atomic absorption spectrometry to measure the Mg content in powdered bone samples only after annealing and in distilled water, which was the "sonication" medium. We obtained evidence for thermally activated transition of Mg from a structurally bound state to a labile state at 680 o C-720 o C. At the same temperature, the Ca-deficient apatite is transformed to stoichiometric apatite. The data presented are evidence that crystals of Ca-deficient bioapatite are surrounded by Ca-enriched surface layers. As a result of thermal transformations at 680 o C-720 o C, all the Mg in the biomineral is found in the non-apatite environment surrounding the crystals and is removed by ultrasonic treatment, while the surface-localized Ca penetrates into the apatite lattice, restoring its stoichiometry.

Journal of Applied Spectroscopy, 2005

ABSTRACT Using x-ray diffraction, electrothermal atomization atomic absorption spectroscopy, and ... more ABSTRACT Using x-ray diffraction, electrothermal atomization atomic absorption spectroscopy, and scanning electron microscopy with an x-ray microanalysis, we have studied the phase decomposition of biogenic and synthetic Mg-containing apatite at 900°C with formation of β-tricalcium-magnesium phosphate (β-TCMP). Employing simplified model representations, we obtained a relation that couples the initial Mg concentration with the degree of transformation of apatite into β-TCMP. It is shown that for the β-TCMP contents measured in bioapatite samples and on replacement of calcium by magnesium to about 8% in this phase the calculated range of Mg concentrations coincides with that available in literature sources (0.2–0.6 wt. %). A comparative investigation of the products of decomposition of biogenic and synthetic apatite by the methods of analysis of the composition and structure has established that the formation of β-TCMP is limited by both the insufficient concentration of magnesium and the small sizes of the crystals. The results of the investigations carried out together with the experimental data known from the literature are indicative of the nonuniform distribution of magnesium in the bulk of crystals of biogenic and synthetic apatite, with its predominant localization at the surface sites of the lattice.

ABSTRACT We have used scanning electron microscopy to study changes in the morphology of the inne... more ABSTRACT We have used scanning electron microscopy to study changes in the morphology of the inner surface of graphite tube furnaces for an atomic absorption spectrometer when modified by tungsten. We have demonstrated the role of the tungsten-containing material as a dividing interlayer between the sample to be dispensed and the carbon component of the furnace. We consider the advantages and disadvantages of furnaces modified by the proposed methods.

ORTHOPAEDICS, TRAUMATOLOGY and PROSTHETICS, 2009

ABSTRACT A number of chitosane/hydroxyl apatite composite materials were synthesized from aqueous... more ABSTRACT A number of chitosane/hydroxyl apatite composite materials were synthesized from aqueous solutions of a biopolymer and soluble salts-precursors. The composites were obtained in the dense and porous variants. The examinations conducted by the methods of X-ray diffraction analysis and infrared spectroscopy showed that apatite crystals in the composites had structural characteristics similar to those of biogenic apatite. Cylindrical rods, made of chitosane/hydroxyl apatite composite materials, were experimentally implanted into the tibial bone of linear laboratory rats in vivo. Histological and histomorphological studies for assessing osteoconductivity were performed 5, 10, 15 and 24 days after the implantation. The specimens were examined by the method of scanning electronic microscopy with X-ray microanalysis for comparing the elemental composition and morphological characteristics of the implant and bone during the integration. The results of the tests make it possible to conclude that chitosane/hydroxyl apatite composites are bioinert and biocompatible. The porous specimens also demonstrated satisfactory osteoconductive properties and were experimentally replaced in vivo by a newly formed bone tissue.

Journal of Biomedical Materials Research Part A, 2011

Chitosan/hydroxyapatite scaffolds could be used for bone regeneration in case the application of ... more Chitosan/hydroxyapatite scaffolds could be used for bone regeneration in case the application of auto-or allografts is impossible. The objective of the present work was to characterize and study in vivo biodegradation of simple chitosan/hydroxyapatite scaffolds. For this purpose, a series of chitosan/hydroxyapatite composites has been synthesized in aqueous medium from chitosan solution and soluble precursor salts by a one step coprecipitation method. A study of in vivo behavior of the materials was then performed using model linear rats. Cylindrical-shaped rods made of the chitosan/hydroxyapatite composite material were implanted into tibial bones of the rats. After 5, 10, 15, and 24 days of implantation, histological and histo-morpho-metric analyses of decalcified specimens were performed to evaluate the stages of biodegradation processes. Calcified specimens were examined by scanning electron microscopy with X-ray microanalysis to compare elemental composition and morphological characteristics of the implant and the bone during integration. Porous chitosan/hydroxyapatite scaffolds have shown osteoconductive properties and have been replaced in the in vivo experiments by newly formed bone tissue. V C 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 96A: 639-647, 2011.

Crystal Research and Technology, 2010

ABSTRACT Composite biomaterials based on chitosan and calcium apatite with different chitosan/apa... more ABSTRACT Composite biomaterials based on chitosan and calcium apatite with different chitosan/apatite ratio were prepared by chemical synthesis of apatite in chitosan solution using one-step co-precipitation method. Initial and annealed samples were characterized by X-ray diffraction, FTIR spectroscopy and scanning electron microscopy coupled to energy-dispersive electron X-ray spectroscopy. The data obtained suggest that the formation of the calcium-phosphate mineral in chitosan solution is substantially modulated by the chemical interaction of the components; apparently, a part of calcium is captured by chitosan and does not participate in the formation of the main mineral phase. The apatite in the composite is calcium-deficient, carbonate-substituted and is composed of dispersed nano-sized crystallites, i.e. has properties that closely resemble those of bone mineral. Varying synthesis, drying and lyophilization conditions, the composite materials can be produced with the desirable chitosan/apatite ratio, both in the dense and porous form. The structural analysis of composite samples after annealing at certain temperatures is examined as an approach to elucidate the mechanism of co-precipitation by one-step method. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Bulletin of The Russian Academy of Sciences: Physics, 2007

The methodical aspects of preparation of biopolymer gels using cryotechniques have been considere... more The methodical aspects of preparation of biopolymer gels using cryotechniques have been considered. By the example of swollen corn starch grains, it is shown that, using a cryostat in scanning electron microscopy, aqueous biopolymer gels can be investigated without artifacts if the sample temperature lies in the range 130–140�C.

Crystal Research and Technology, 2013

Complementary experimental techniques were applied to characterize bioapatite nanocrystals from p... more Complementary experimental techniques were applied to characterize bioapatite nanocrystals from pathological cardiovascular deposits. The investigated collection included the leaflets from aortic valve, leaflets from mitral valve, leaflets from tricuspid valve and calcified aorta's wall. XRD, EDX and FTIR data have shown that all studied samples consist of imperfect apatite with different crystallinity and variable chemical composition. In accordance with TEM data, the crystals of pathological calcified deposits frequently have oblong or rod-like shape (length of 60-90 nanometers, width of 20-30 nanometers). At the same time, in the SEM and TEM experiments, the complex spheroid assemblies and planar sheet-like shaped formations with crystal structure close to apatite were observed. Probably, the different shape and morphology of the particles are caused by different ways of crystal nucleation and growth, although the exact mechanisms remain an open question.

Ceska a slovenska oftalmologie : casopis Ceske oftalmologicke spolecnosti a Slovenske oftalmologicke spolecnosti, 2014

The authors have described the case of pathological biomineralization of ocular posterior chamber... more The authors have described the case of pathological biomineralization of ocular posterior chamber. Histological examination of affected eye shells revealed inflammation, oedema, dyscirculatory violations, and signs of dystrophic calcification. Structural-phase and chemical analyses of calcification have revealed that the biomineral consists of hydroxyapatite with relatively small crystallite size and defective crystal lattice. In the described case the formation of pathological biomineral in the vision organ was initiated by penetrating wound. Eye injury might have caused a hemophthalmus and chronic inflammatory reaction in the shells, these processes eventually led to the organ subatrophy and to the development of dystrophic and necrobiotic changes in the tissues. Pathological biomineralization in the affected organ developed as a type of dystrophic calcification.Key words: eye, pathological biomineralization, hydroxyapatite.

Journal of Nano- and Electronic Physics, 2016

Crystal Research and Technology, 2013

ABSTRACT Complementary experimental techniques were applied to characterize bioapatite nanocrysta... more ABSTRACT Complementary experimental techniques were applied to characterize bioapatite nanocrystals from pathological cardiovascular deposits. The investigated collection included the leaflets from aortic valve, leaflets from mitral valve, leaflets from tricuspid valve and calcified aorta's wall. XRD, EDX and FTIR data have shown that all studied samples consist of imperfect apatite with different crystallinity and variable chemical composition. In accordance with TEM data, the crystals of pathological calcified deposits frequently have oblong or rod-like shape (length of 60-90 nanometers, width of 20-30 nanometers). At the same time, in the SEM and TEM experiments, the complex spheroid assemblies and planar sheet-like shaped formations with crystal structure close to apatite were observed. Probably, the different shape and morphology of the particles are caused by different ways of crystal nucleation and growth, although the exact mechanisms remain an open question.

Ceska a slovenska oftalmologie : casopis Ceske oftalmologicke spolecnosti a Slovenske oftalmologicke spolecnosti, 2014

The authors have described the case of pathological biomineralization of ocular posterior chamber... more The authors have described the case of pathological biomineralization of ocular posterior chamber. Histological examination of affected eye shells revealed inflammation, oedema, dyscirculatory violations, and signs of dystrophic calcification. Structural-phase and chemical analyses of calcification have revealed that the biomineral consists of hydroxyapatite with relatively small crystallite size and defective crystal lattice. In the described case the formation of pathological biomineral in the vision organ was initiated by penetrating wound. Eye injury might have caused a hemophthalmus and chronic inflammatory reaction in the shells, these processes eventually led to the organ subatrophy and to the development of dystrophic and necrobiotic changes in the tissues. Pathological biomineralization in the affected organ developed as a type of dystrophic calcification.Key words: eye, pathological biomineralization, hydroxyapatite.

Journal of Biomedical Materials Research Part A, 2011

Chitosan/hydroxyapatite scaffolds could be used for bone regeneration in case the application of ... more Chitosan/hydroxyapatite scaffolds could be used for bone regeneration in case the application of auto-or allografts is impossible. The objective of the present work was to characterize and study in vivo biodegradation of simple chitosan/hydroxyapatite scaffolds. For this purpose, a series of chitosan/hydroxyapatite composites has been synthesized in aqueous medium from chitosan solution and soluble precursor salts by a one step coprecipitation method. A study of in vivo behavior of the materials was then performed using model linear rats. Cylindrical-shaped rods made of the chitosan/hydroxyapatite composite material were implanted into tibial bones of the rats. After 5, 10, 15, and 24 days of implantation, histological and histo-morpho-metric analyses of decalcified specimens were performed to evaluate the stages of biodegradation processes. Calcified specimens were examined by scanning electron microscopy with X-ray microanalysis to compare elemental composition and morphological characteristics of the implant and the bone during integration. Porous chitosan/hydroxyapatite scaffolds have shown osteoconductive properties and have been replaced in the in vivo experiments by newly formed bone tissue. V C 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 96A: 639-647, 2011.

ORTHOPAEDICS, TRAUMATOLOGY and PROSTHETICS, 2009

ABSTRACT A number of chitosane/hydroxyl apatite composite materials were synthesized from aqueous... more ABSTRACT A number of chitosane/hydroxyl apatite composite materials were synthesized from aqueous solutions of a biopolymer and soluble salts-precursors. The composites were obtained in the dense and porous variants. The examinations conducted by the methods of X-ray diffraction analysis and infrared spectroscopy showed that apatite crystals in the composites had structural characteristics similar to those of biogenic apatite. Cylindrical rods, made of chitosane/hydroxyl apatite composite materials, were experimentally implanted into the tibial bone of linear laboratory rats in vivo. Histological and histomorphological studies for assessing osteoconductivity were performed 5, 10, 15 and 24 days after the implantation. The specimens were examined by the method of scanning electronic microscopy with X-ray microanalysis for comparing the elemental composition and morphological characteristics of the implant and bone during the integration. The results of the tests make it possible to conclude that chitosane/hydroxyl apatite composites are bioinert and biocompatible. The porous specimens also demonstrated satisfactory osteoconductive properties and were experimentally replaced in vivo by a newly formed bone tissue.

Crystal Research and Technology, 2010

ABSTRACT Composite biomaterials based on chitosan and calcium apatite with different chitosan/apa... more ABSTRACT Composite biomaterials based on chitosan and calcium apatite with different chitosan/apatite ratio were prepared by chemical synthesis of apatite in chitosan solution using one-step co-precipitation method. Initial and annealed samples were characterized by X-ray diffraction, FTIR spectroscopy and scanning electron microscopy coupled to energy-dispersive electron X-ray spectroscopy. The data obtained suggest that the formation of the calcium-phosphate mineral in chitosan solution is substantially modulated by the chemical interaction of the components; apparently, a part of calcium is captured by chitosan and does not participate in the formation of the main mineral phase. The apatite in the composite is calcium-deficient, carbonate-substituted and is composed of dispersed nano-sized crystallites, i.e. has properties that closely resemble those of bone mineral. Varying synthesis, drying and lyophilization conditions, the composite materials can be produced with the desirable chitosan/apatite ratio, both in the dense and porous form. The structural analysis of composite samples after annealing at certain temperatures is examined as an approach to elucidate the mechanism of co-precipitation by one-step method. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

(Получено 12.02.2016; в отредактированной форме – 02.03.2016; опубликована online 15.03.2016) В р... more (Получено 12.02.2016; в отредактированной форме – 02.03.2016; опубликована online 15.03.2016) В работе приведены результаты исследований морфологии, структуры, элементного и фазового со-става кальцинированных фрагментов патологических образований щитовидной железы. Методами рентгеновской дифракции и инфракрасной спектроскопии установлено, что все исследованные пато-логические кальцификаты представляет собой дефектный карбонатзамещенный апатит кальция Ca10(PO4)6(OH)2. Показано, что применение просвечивающей электронной микроскопии в комбинации с микродифракцией электронов позволяет выявить некоторые структурные и морфологические осо-бенности кристаллов апатита щитовидной железы, не обнаруживаемые другими методами. Благода-ря этому, при условии применения тонкого препарирования на стадии анатомических исследований и подготовки пробы, может быть реализован локальный морфологический и структурный анализ мине-ральных составляющих депозита как при одном и том же клиническом случае, так и при их широком разнообразии.

—The methodical aspects of preparation of biopolymer gels using cryotechniques have been consider... more —The methodical aspects of preparation of biopolymer gels using cryotechniques have been considered. By the example of swollen corn starch grains, it is shown that, using a cryostat in scanning electron microscopy, aqueous biopolymer gels can be investigated without artifacts if the sample temperature lies in the range 130–140°C. In many areas of production, biotechnology is based on the translation of biopolymers into the gel state. A biopolymer gel is a spatial network (framework) with structural elements relatively rigidly connected with each other; each structural element can undergo reversible deformation upon bending or extension. The morphology of polymer gels is fairly complex, since twophase (nonequilibrium) systems are characterized by the formation of a number of intermediate states. In gelforming systems, layering is never completed and their morphology is a mixture of the primary structure and the structure formed as a result of partial fracture of the matrix phase [1]. In the modern stage of development of new materials with specific properties, the role of electron microscopy continuously increases. This method became a routine tool for monitoring the structure of various materials, especially in the nanotechnology research [2–4]. In the use of the methods of electron microscopy, it is necessary to take into account that the exact quantitative analytical methods that are used in modern instruments are limited by the uncertainties related to the sample preparation for analysis. It should be noted that ambiguous results were obtained in the studies devoted to the methods for preparing biopolymer gels, and the conclusions drawn contradict the data of other studies [5, 6]. The most widespread methods for preparing biopolymer gels are as follows: negative staining, freeze–etching, and freeze–fracture for transmission electron microscopy (TEM) and freeze–drying for scanning electron microscopy (SEM). Ultramicrotomy, cryomicrotomy, and critical point drying are more rarely used. In this study, we analyzed the possibilities of the following cryotechniques for biopolymer gel preparation: freeze–drying, freeze–fracture, and investigation in a cryostat. As an object of study, we chose swollen corn starch grains. Starch and starch-containing raw materials are widely used in food industry as gelling agents, foam and emulsion thickeners, and other nonfood materials. The experiment was performed using SEM (S-2500, Hitachi) and TEM (EM-125, Sumy, Ukraine). In addition, a REM-100U scanning electron microscope with a RUPIK cryostat (Sumy, Ukraine) was applied. Using RUPIK and the cryomicrotome built-in in the microscope, one can perform layer-by-layer analysis of a frozen sample at low temperatures that are used in cryotechniques: from –100 to – 140°C. The RUPIK design features make it possible to investigate the same portion of a sample by SEM and TEM, since a carbon–platinum replica can be deposited on the sample surface by laser sputtering of the material directly in the electron microscope; such a procedure excludes sample heating during its preparation. To determine the sample freezing rate, we used an ISK indicator, which allows thermographic detection of small ice crystals when cryotechniques are used. It is known

Journal of Applied Spectroscopy, 2006

We have attempted to use heat treatment followed by ultrasonic treatment to separate the apatite ... more We have attempted to use heat treatment followed by ultrasonic treatment to separate the apatite from the non-apatite components of bone mineral in samples from different animals. The Mg content and the Ca/P ratio in the temperature range 560 o C-720 o C in the samples before and after ultrasonic treatment were determined by electron-probe x-ray microanalysis. Furthermore, we used atomic absorption spectrometry to measure the Mg content in powdered bone samples only after annealing and in distilled water, which was the "sonication" medium. We obtained evidence for thermally activated transition of Mg from a structurally bound state to a labile state at 680 o C-720 o C. At the same temperature, the Ca-deficient apatite is transformed to stoichiometric apatite. The data presented are evidence that crystals of Ca-deficient bioapatite are surrounded by Ca-enriched surface layers. As a result of thermal transformations at 680 o C-720 o C, all the Mg in the biomineral is found in the non-apatite environment surrounding the crystals and is removed by ultrasonic treatment, while the surface-localized Ca penetrates into the apatite lattice, restoring its stoichiometry.

Journal of Applied Spectroscopy, 2005

ABSTRACT Using x-ray diffraction, electrothermal atomization atomic absorption spectroscopy, and ... more ABSTRACT Using x-ray diffraction, electrothermal atomization atomic absorption spectroscopy, and scanning electron microscopy with an x-ray microanalysis, we have studied the phase decomposition of biogenic and synthetic Mg-containing apatite at 900°C with formation of β-tricalcium-magnesium phosphate (β-TCMP). Employing simplified model representations, we obtained a relation that couples the initial Mg concentration with the degree of transformation of apatite into β-TCMP. It is shown that for the β-TCMP contents measured in bioapatite samples and on replacement of calcium by magnesium to about 8% in this phase the calculated range of Mg concentrations coincides with that available in literature sources (0.2–0.6 wt. %). A comparative investigation of the products of decomposition of biogenic and synthetic apatite by the methods of analysis of the composition and structure has established that the formation of β-TCMP is limited by both the insufficient concentration of magnesium and the small sizes of the crystals. The results of the investigations carried out together with the experimental data known from the literature are indicative of the nonuniform distribution of magnesium in the bulk of crystals of biogenic and synthetic apatite, with its predominant localization at the surface sites of the lattice.

ABSTRACT We have used scanning electron microscopy to study changes in the morphology of the inne... more ABSTRACT We have used scanning electron microscopy to study changes in the morphology of the inner surface of graphite tube furnaces for an atomic absorption spectrometer when modified by tungsten. We have demonstrated the role of the tungsten-containing material as a dividing interlayer between the sample to be dispensed and the carbon component of the furnace. We consider the advantages and disadvantages of furnaces modified by the proposed methods.

ORTHOPAEDICS, TRAUMATOLOGY and PROSTHETICS, 2009

ABSTRACT A number of chitosane/hydroxyl apatite composite materials were synthesized from aqueous... more ABSTRACT A number of chitosane/hydroxyl apatite composite materials were synthesized from aqueous solutions of a biopolymer and soluble salts-precursors. The composites were obtained in the dense and porous variants. The examinations conducted by the methods of X-ray diffraction analysis and infrared spectroscopy showed that apatite crystals in the composites had structural characteristics similar to those of biogenic apatite. Cylindrical rods, made of chitosane/hydroxyl apatite composite materials, were experimentally implanted into the tibial bone of linear laboratory rats in vivo. Histological and histomorphological studies for assessing osteoconductivity were performed 5, 10, 15 and 24 days after the implantation. The specimens were examined by the method of scanning electronic microscopy with X-ray microanalysis for comparing the elemental composition and morphological characteristics of the implant and bone during the integration. The results of the tests make it possible to conclude that chitosane/hydroxyl apatite composites are bioinert and biocompatible. The porous specimens also demonstrated satisfactory osteoconductive properties and were experimentally replaced in vivo by a newly formed bone tissue.

Journal of Biomedical Materials Research Part A, 2011

Chitosan/hydroxyapatite scaffolds could be used for bone regeneration in case the application of ... more Chitosan/hydroxyapatite scaffolds could be used for bone regeneration in case the application of auto-or allografts is impossible. The objective of the present work was to characterize and study in vivo biodegradation of simple chitosan/hydroxyapatite scaffolds. For this purpose, a series of chitosan/hydroxyapatite composites has been synthesized in aqueous medium from chitosan solution and soluble precursor salts by a one step coprecipitation method. A study of in vivo behavior of the materials was then performed using model linear rats. Cylindrical-shaped rods made of the chitosan/hydroxyapatite composite material were implanted into tibial bones of the rats. After 5, 10, 15, and 24 days of implantation, histological and histo-morpho-metric analyses of decalcified specimens were performed to evaluate the stages of biodegradation processes. Calcified specimens were examined by scanning electron microscopy with X-ray microanalysis to compare elemental composition and morphological characteristics of the implant and the bone during integration. Porous chitosan/hydroxyapatite scaffolds have shown osteoconductive properties and have been replaced in the in vivo experiments by newly formed bone tissue. V C 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 96A: 639-647, 2011.

Crystal Research and Technology, 2010

ABSTRACT Composite biomaterials based on chitosan and calcium apatite with different chitosan/apa... more ABSTRACT Composite biomaterials based on chitosan and calcium apatite with different chitosan/apatite ratio were prepared by chemical synthesis of apatite in chitosan solution using one-step co-precipitation method. Initial and annealed samples were characterized by X-ray diffraction, FTIR spectroscopy and scanning electron microscopy coupled to energy-dispersive electron X-ray spectroscopy. The data obtained suggest that the formation of the calcium-phosphate mineral in chitosan solution is substantially modulated by the chemical interaction of the components; apparently, a part of calcium is captured by chitosan and does not participate in the formation of the main mineral phase. The apatite in the composite is calcium-deficient, carbonate-substituted and is composed of dispersed nano-sized crystallites, i.e. has properties that closely resemble those of bone mineral. Varying synthesis, drying and lyophilization conditions, the composite materials can be produced with the desirable chitosan/apatite ratio, both in the dense and porous form. The structural analysis of composite samples after annealing at certain temperatures is examined as an approach to elucidate the mechanism of co-precipitation by one-step method. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Bulletin of The Russian Academy of Sciences: Physics, 2007

The methodical aspects of preparation of biopolymer gels using cryotechniques have been considere... more The methodical aspects of preparation of biopolymer gels using cryotechniques have been considered. By the example of swollen corn starch grains, it is shown that, using a cryostat in scanning electron microscopy, aqueous biopolymer gels can be investigated without artifacts if the sample temperature lies in the range 130–140�C.

Crystal Research and Technology, 2013

Complementary experimental techniques were applied to characterize bioapatite nanocrystals from p... more Complementary experimental techniques were applied to characterize bioapatite nanocrystals from pathological cardiovascular deposits. The investigated collection included the leaflets from aortic valve, leaflets from mitral valve, leaflets from tricuspid valve and calcified aorta's wall. XRD, EDX and FTIR data have shown that all studied samples consist of imperfect apatite with different crystallinity and variable chemical composition. In accordance with TEM data, the crystals of pathological calcified deposits frequently have oblong or rod-like shape (length of 60-90 nanometers, width of 20-30 nanometers). At the same time, in the SEM and TEM experiments, the complex spheroid assemblies and planar sheet-like shaped formations with crystal structure close to apatite were observed. Probably, the different shape and morphology of the particles are caused by different ways of crystal nucleation and growth, although the exact mechanisms remain an open question.

Ceska a slovenska oftalmologie : casopis Ceske oftalmologicke spolecnosti a Slovenske oftalmologicke spolecnosti, 2014

The authors have described the case of pathological biomineralization of ocular posterior chamber... more The authors have described the case of pathological biomineralization of ocular posterior chamber. Histological examination of affected eye shells revealed inflammation, oedema, dyscirculatory violations, and signs of dystrophic calcification. Structural-phase and chemical analyses of calcification have revealed that the biomineral consists of hydroxyapatite with relatively small crystallite size and defective crystal lattice. In the described case the formation of pathological biomineral in the vision organ was initiated by penetrating wound. Eye injury might have caused a hemophthalmus and chronic inflammatory reaction in the shells, these processes eventually led to the organ subatrophy and to the development of dystrophic and necrobiotic changes in the tissues. Pathological biomineralization in the affected organ developed as a type of dystrophic calcification.Key words: eye, pathological biomineralization, hydroxyapatite.