Search

The development of magnesium calcium phosphate bone cements (MCPCs) has garnered substantial attention. MCPCs are bioactive and biodegradable and have appropriate mechanical and antimicrobial properties for use in reconstructive surgery. In this study, the cement powders based on a (Ca + Mg)/P = 2 system doped with Zn2+ at 0.5 and 1.0 wt.% were obtained and investigated. After mixing with a cement liquid, the structural and phase composition, morphology, chemical structure, setting time, compressive strength, degradation behavior, solubility, antibacterial activities, and in vitro behavior of the cement materials were examined. A high compressive strength of 48 ± 5 MPa (mean ± SD) was achieved for the cement made from Zn2+ 1.0 wt.%-substituted powders. Zn2+ introduction led to antibacterial activity against Staphylococcus aureus and Escherichia coli strains, with an inhibition zone diameter of up to 8 mm. Biological assays confirmed that the developed cement is cytocompatible and promising as a potential bone substitute in reconstructive surgery.

The development of magnesium calcium phosphate bone cements (MCPCs) have garnered big attention. MCPCs are bioactive and biodegradable and have appropriate mechanical and antimicrobial properties for use in reconstructive surgery. In this study, the cement powders based on a (Ca + Mg)/P = 2 system doped with Zn2+ at 0.5 and 1.0 wt.% were obtained and investigated. After the mixing with a cement liquid, structural and phase composition, morphology, chemical structure, setting time, compressive strength, degradation behavior, solubility, antibacterial activities, and in vitro behaviour of the cement materials were examined. A high compressive strength of 48 ± 5 MPa (mean ± SD) was achieved for the cement made from Zn2+ 1.0-wt.%-substituted powders. The Zn2+ introduction led to antibacterial activity against Staphylococcus aureus and Escherichia coli strains, with an inhibition zone diameter up to 8 mm. Biological assays confirmed that the developed cements are cytocompatible and promising as a potential bone substitute in reconstructive surgery.

Octacalcium phosphate (OCP), a new-generation bone substitute material, is a considered precursor of the biological bone apatite. The two-layered structure of OCP contains the apatitic and hydrated layers and is intensively involved in ion-exchange surface reactions, which results in OCP hydrolysis to hydroxyapatite and adsorption of ions or molecular groups presented in the environment. During various in vitro procedures, such as biomaterial solubility, additive release studies, or the functionalization technique, several model solutions are applied. The composition of the environmental solution affects the degree and rate of OCP hydrolysis, its surface reactivity, and further in vitro and in vivo properties. The performed study was aimed to track the structural changes of OCP-based materials while treating in the most popular model solutions of pH values 7.2-7.4: simulated body fluid (SBF), Dulbecco's phosphate-buffered saline (DPBS), supersaturated calcification solution (SCS), normal saline (NS), and Dulbecco's modified Eagle's medium (DMEM). Various degrees of OCP hydrolysis and/or precipitate formation were achieved through soaking initial OCP granules in the model solutions. Detailed data of X-ray diffraction, Fourier-transform infrared spectroscopy, atomic emission spectrometry with inductively coupled plasma, and scanning electron microscopy are presented. Cultivation of osteosarcoma cells was implemented on OCP pre-treated in DMEM for 1-28 days. It was shown that NS mostly degraded the OCP structure. DPBS slightly changed the OCP structure during the first treatment term, and during further terms, the crystals got thinner and OCP hydrolysis took place. Treatment in SBF and SCS caused the precipitate formation along with OCP hydrolysis, with a larger contribution of SCS solution to precipitation. Pre-treating in DMEM enhanced the cytocompatibility of materials. As a result, on performing the in vitro procedures, careful selection of the contact solution should be made to avoid the changes in materials structure and properties and get adequate results.

We have studied manganese-containing calcium phosphates differing in manganese content and phase composition. At a manganese content of 0.15 wt %, the whitlockite content is ~90 wt % and the calcium pyrophosphate content is ~10 wt %. Increasing the manganese content to 1.49 wt % reduces the whitlockite content to ~70 wt % and increases the calcium pyrophosphate content to ~30 wt %. IR spectroscopy results show that the samples calcined at 400°C have the apatite structure, whereas raising the calcination temperature to 900°C leads to the formation of the whitlockite structure and calcium pyrophosphate. Active sintering begins in the range 920–1050°C. Raising the firing temperature to 1200°C leads to the formation of a densely sintered structure, with melted regions and an average grain size from 15 to 25 μm. With increasing manganese content, the grain size of the ceramics decreases. Our results on cytotoxic properties demonstrate that the samples are not cytotoxic and maintain cell proliferation and spreading. The cytotoxicity of the samples is insensitive to the calcium pyrophosphate and manganese concentrations. The powders and ceramics prepared in this study can be used as key components of novel materials for bone tissue engineering.

Powders based on β-tricalcium phosphate (β-TCP) containing sulphate groups at up to 12.0 mol.% were synthesised by chemical precipitation from aqueous solutions. The obtained materials were characterised by X-ray phase analysis, Fourier transform infrared spectroscopy, measurement of specific surface area, scanning electron microscopy, energy dispersive analysis, synchronous thermal analysis, mass spectra investigations and biological assays. It was established that during the synthesis, the obtained materials lose the sulphate groups in the course of heat treatment at 900 or 1200 °C. These groups stabilise low-temperature β-TCP, but when introduced at a high concentration, the sulphate groups contribute to the formation of hydroxyapatite during the heat treatment. Specific surface area of the powders proved to be in the range 81.7–96.5 m2/g. Results of biological assays showed cytocompatibility of both pure β-TCP and samples of sulphate-containing β-TCP. Additionally, matrix properties in the culture of MG-63 cells were revealed in all samples. Thus, the obtained materials are promising for biomedical applications.

Octacalcium phosphate (OCP, Ca8H2(PO4)6·5H2O) is known to be a possible precursor of biological hydroxyapatite formation of organic bone tissue. OCP has higher biocompatibility and osseointegration rate compared to other calcium phosphates. In this work, the synthesis of low-temperature calcium phosphate compounds and substituted forms of those at physiological temperatures is shown. Strontium is used to improve bioactive properties of the material. Strontium was inserted into the OCP structure by ionic substitution in solutions. The processes of phase formation of low-temperature OCP with theoretical substitution of strontium for calcium up to 50 at.% in conditions close to physiological, i.e., temperature 35–37 °C and normal pressure, were described. The effect of strontium substitution range on changes in the crystal lattice of materials, the microstructural features, surface morphology and biological properties in vitro has been established. The results of the study indicate the effectiveness of using strontium in OCP for improving biocompatibility of OCP based composite materials intended for bone repair.

An original method is proposed for the production of methylcellulose-based film materials. The method is based on obtaining a homogeneous MC mixture with sodium alginate in an aqueous solution and subsequently crosslinking the mixture of the polymers with iron salts owing to their interaction with the blocks of L-guluronic acid in the alginate.

Methylcellulose (MC) is now widely used in medicine to fill defects of damaged tissues. A new method is proposed to improve the stability of MC-based materials in aqueous media using non-toxic reagents. MC–alginate blend films are crosslinked by iron(II) and iron(III) ions using different iron salts. The resulting films are stable in physiological solution for about 14 days. Mechanical tests of the dried films show an increase in the Young's modulus with iron concentration in solutions. Mossbauer spectroscopy data show that the films contain Fe3+ ions alone irrespective of whether chlorides of Fe2+ or Fe3+ are applied as crosslinking agents. The use of ascorbic acid as a complexing agent prevents Fe2+ from oxidation. The obtained materials are stable for at least half a year. The resulting films facilitate the growth of human fibroblasts on their surface.

For bone replacement materials, osteoconductive, osteoinductive, and osteogenic properties are desired. The bacterial resistance and the need for new antibacterial strategies stand among the most challenging tasks of the modern medicine. In this work, brushite cements based on powders of Zinc (Zn) (1.4 wt%) substituted tricalcium phosphate (β-TCP) and non-substituted β-TCP were prepared and investigated. Their initial and final phase composition, time of setting, morphology, pH evolution, and compressive strength are reported. After soaking for 60 days in physiological solution, the cements transformed into a mixture of brushite and hydroxyapatite. Antibacterial activity of the cements against Enterococcus faecium, Escherichia coli, and Pseudomonas aeruginosa bacteria strains was attested. The absence of cytotoxicity of cements was proved for murine fibroblast NCTC L929 cells. Moreover, the cell viability on the β-TCP cement containing Zn2+ ions was 10% higher compared to the β-TCP cement without zinc. The developed cements are perspective for applications in orthopedics and traumatology.

Mesoporous hydroxyapatite (HA) and iron(III)-doped HA (Fe-HA) are attractive materials for biomedical, catalytic, and environmental applications. In the present study, the nanopowders of HA and Fe-HA with a specific surface area up to 194.5 m2/g were synthesized by a simple precipitation route using iron oxalate as a source of Fe3+ cations. The influence of Fe3+ amount on the phase composition, powders morphology, Brunauer–Emmett–Teller (BET) specific surface area (S), and pore size distribution were investigated, as well as electron paramagnetic resonance and Mössbauer spectroscopy analysis were performed. According to obtained data, the Fe3+ ions were incorporated in the HA lattice, and also amorphous Fe oxides were formed contributed to the gradual increase in the S and pore volume of the powders. The Density Functional Theory calculations supported these findings and revealed Fe3+ inclusion in the crystalline region with the hybridization among Fe-3d and O-2p orbitals and a partly covalent bond formation, whilst the inclusion of Fe oxides assumed crystallinity damage and rather occurred in amorphous regions of HA nanomaterial. In vitro tests based on the MG-63 cell line demonstrated that the introduction of Fe3+ does not cause cytotoxicity and led to the enhanced cytocompatibility of HA.

Nanocrystalline 3 mol% yttria-tetragonal zirconia polycrystal (3Y-TZP) ceramic powder containing 5 wt.% Al2O3 with 64 m2/g specific area was synthesized through precipitation method. Different amounts of Co (0&ndash, 3 mol%) were introduced into synthesized powders, and ceramic materials were obtained by heat treatment in the air for 2 h at 1350&ndash, 1550 &deg, C. The influence of Co addition on the sintering temperature, phase composition, microstructure, mechanical and biomedical properties of the obtained composite materials, and on the resolution of the digital light processing (DLP) printed and sintered ceramic samples was investigated. The addition of a low amount of Co (0.33 mol%) allows us to decrease the sintering temperature, to improve the mechanical properties of ceramics, to preserve the nanoscale size of grains at 1350&ndash, 1400 &deg, C. The further increase of Co concentration resulted in the formation of both substitutional and interstitial sites in solid solution and appearance of CoAl2O4 confirmed by UV-visible spectroscopy, which stimulates grain growth. Due to the prevention of enlarging grains and to the formation of the dense microstructure in ceramic based on the tetragonal ZrO2 and Al2O3 with 0.33 mol% Co the bending strength of 720 &plusmn, 33 MPa was obtained after sintering at 1400 &deg, C. The obtained materials demonstrated the absence of cytotoxicity and good cytocompatibility. The formation of blue CoAl2O4 allows us to improve the resolution of DLP based stereolithographic printed green bodies and sintered samples of the ceramics based on ZrO2-Al2O3. The developed materials and technology could be the basis for 3D manufacturing of bioceramic implants for medicine.

The development of new materials with antibacterial properties and the scope to decrease or eliminate the excessive antibiotic use is an urgent priority due to the growing antibiotic resistance-related mortalities. New bone substitute materials with intrinsic antibacterial characteristics are highly requested for various clinical applications. In this study, the choice of copper ions as substitutes for calcium in tricalcium phosphate (TCP) has been justified by their pronounced broad-spectrum antibacterial properties. Copper-substituted TCP (Cu-TCP) ceramics with the copper content of 1.4 and 0.1 wt% were synthesized by mechano-chemical activation. X-ray diffraction (XRD) analyses established that both pure and copper-containing compounds adopted the structure of whitlockite (β-TCP). XRD and electron paramagnetic resonance (EPR) spectroscopy revealed the partial isovalent substitution of calcium ions with copper ions in the β-TCP lattice. With the use of infrared and EPR spectroscopies, it was detected that carbonate ions got incorporated into the β-TCP structure during the synthesis procedure. By releasing the tension in the M(5)O6 octahedron consequential to the lower Ca O bond length than the corresponding sum of ionic radii, the substitution of calcium with smaller copper ions stabilizes the structure of β-TCP. As concluded form the thermal analyses, the introduction of Cu prevented the polymorphic transformation of β- to α-TCP. At the same time, the introduction of Cu to the β-TCP structure enhanced the crystal growth and porosity of the ceramics, which had a positive effect on the cytocompatibility of the material. The MTT colorimetric assay showed that the metabolic activity of the mouse fibroblast NCTC L929 cell line during 24 h of incubation with 3-day extracts from Cu-TCP (1.4 wt%) and β-TCP pellets in the cell culture medium was similar to the negative control, indicating the absence of any inhibitory effects on cells. The seeding and the growth of human dental pulp stem cells on the surface of Cu-TCP (1.4 wt%) and β-TCP ceramics also showed the absence of any signs of cytotoxicity. Finally, microbiological assays demonstrated the antibacterial activity of Cu-TCP ceramics against Escherichia coli and Salmonella enteritidis, whereas β-TCP did not exhibit such an activity. Overall, the addition of Cu ions to β-TCP improves its antibacterial properties without diminishing the biocompatibility of the material, thus making it more attractive than pure β-TCP for clinical applications such as synthetic bone grafts and orthopaedic implant coatings.

This paper examines the physicochemical properties and microstructure of brushite calcium phosphate cements possessing strength acceptable for application in surgery (15–20 MPa) and ensuring an optimal acidity (pH 6.5–7.5) of solutions in contact with them. Holding in a physiological saline produces significant changes in the microstructure of the cement relative to that before immersion in the solution: it causes a transformation of the most soluble components into platelike hydroxyapatite crystals.

New magnesium-substituted bone cements containing MgO as a separate phase have been developed and demonstrated enhanced mechanical properties and cytological compatibility.

Novel materials with a variety of properties, such as biocompatibility, antibacterial activity, interconnected porosity, and functionalities combined in one, are required for regenerative medicine. Porous β-tricalcium phosphate (β-TCP) ceramics doped with Cu2+, Zn2+, Ag+, and Fe3+ ions in the concentrations of less than 0.5 wt.% were synthesized and investigated. The obtained samples were analyzed by the diversity of analytical tools. The structure, solubility, and antimicrobial properties of the porous ceramics are shown to be very sensitive to the presence and the type of the cationic substituent. It opens the way to manage structure and properties of the materials for bone tissue regeneration by co-doping of the initial matrix simultaneously with different types of substituent ions.

Bioactive manganese (Mn)-doped ceramic coatings for intraosseous titanium (Ti) implants are developed. Arc plasma deposition procedure is used for coatings preparation. X-ray Diffraction, Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy, and Electron Paramagnetic Resonance (EPR) methods are applied for coatings characterization. The coatings are homogeneous, composed of the main phase &alpha, tricalcium phosphate (&alpha, TCP) (about 67%) and the minor phase hydroxyapatite (about 33%), and the Mn content is 2.3 wt%. EPR spectroscopy demonstrates that the Mn ions are incorporated in the TCP structure and are present in the coating in Mn2+ and Mn3+ oxidation states, being aggregated in clusters. The wetting contact angle of the deposited coatings is suitable for cells&rsquo, adhesion and proliferation. In vitro soaking in physiological solution for 90 days leads to a drastic change in phase composition, the transformation into calcium carbonate and octacalcium phosphate takes place, and no more Mn is present. The absence of antibacterial activity against Escherichia coli, Enterococcus faecalis, and Pseudomonas aeruginosa bacteria strains is observed. A study of the metabolic activity of mouse fibroblasts of the NCTC L929 cell line on the coatings using the MTT (dye compound 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) test demonstrates that there is no toxic effect on the cell culture. Moreover, the coating material supports the adhesion and proliferation of the cells. A good adhesion, spreading, and proliferative activity of the human tooth postnatal dental pulp stem cells (DPSC) is demonstrated. The developed coatings are promising for implant application in orthopedics and dentistry.

Severe plastic deformations lead to structural transformations in dense microcrystalline hydroxyapatite (HA, Ca 10 (PO 4 ) 6 (OH) 2 ) ceramics and particularly to formation of nanocrystalline structure with α-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 (TEM). Our results are in agreement with the cluster mechanism of the HA structure (Ca 9 (PO 4 ) 6 , Ca 3 (PO 4 ) 2 and PO 4 3 − ) model representing deformation of HA by cluster fragmentation and cluster-boundary “sliding”.

In this study, the phase development in the cement system α-TCP–OCP with phosphoric acid as a setting liquid was studied. The most promising formulation of α-TCP (60 wt%) and OCP (40 wt%) is proposed. This cement has the following characteristics: setting time 10 min, pH = 6.7, the compressive strength about 30 MPa, and high dissolution rate in an isotonic solution; the final wt% composition of α-TCP/DCPD/HA/OCP equals 27/38/20/15. Energy dispersive X-ray diffraction techniques were used for in situ monitoring of the processes taking place in the cement in real time.

Composite powders in the calcium carbonate (CC) – hydroxyapatite (HA) system with carbonate content up to 50 wt. % were synthesized by the precipitation from aqueous solution and characterized in detail. Specific area of the powders decreases with an increase in carbonate content due to appearance of large elongated CC crystals of about 0,5 micrometer size. The use of highly active to sintering nanodisperse powders resulted in lowering of sintering temperature below 7200C, preventing thermal decomposition. Ceramics of about 20 wt.% carbonate content revealed the highest strength of about 77 MPa, having the grain size of about 100 nm. According to in vitro testing, the materials are non toxic for human fibroblast cells.

The present study is focused on the in vitro study of the biphasic octacalcium phosphate (OCP)-dicalcium phosphate dihydrate (DCPD) system transformations in simulated body fluid (SBF) for possible applications as bone substitute materials. The aim of this paper is to outline the role of the additional component DCPD during a transformation/crystallization processes. Energy dispersive X-ray diffraction and FTIR spectroscopy techniques were used for in situ monitoring of the processes taking place in the system in real time. Morphological investigations were performed applying the scanning electron microscopy technique. Several OCP-DCPD combinations were investigated: (1) 100% OCP; (2) 70% OCP-30% DCPD; (3) 100% DCPD. The obtained experimental results allowed us to conclude that when only OCP is present in SBF, the formation of carbonated hydroxyapatite takes place, whereas for the OCP—DCPD (30%) system in SBF, less kinetically favorable hydroxyapatite (HA) is formed. The additional component (DCPD) influences significantly the structural behavior of hydroxyapatite, acting as the HA crystallization inhibition agent. By means of this approach, allowing for the control of the HA crystallization, the calcium phosphate based biomaterials can be suitably modified for implant use in bone tissue engineering. The results obtained in this work provided some insights into the biomineralization mechanism.

In this work, an anomalous microscopic and macroscopic behavior during the hardening process of a calcium phosphate cement, based on anhydrous dicalcium phosphate, was observed. Indeed, the standard compressive strength measurements provided completely unexpected results, which encouraged a deeper investigation by means of X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron and atomic force microscopies. The energy dispersive X-ray diffraction mode was preferred to the conventional angular dispersive one, the former being particularly suitable for the real-time studies, allowing us to follow the hardening process in situ and to confirm that the investigated cement undergoes a long-time crystallization much more complex than expected. Indeed, the sequence of diffraction patterns exhibited anomalous intensity modulations (corresponding to structural changes taking place upon hardening) being consistent, and even in phase, with the variations of the compressive strength. These anomalous intensity modulations were confirmed also by the in situ time-resolved Fourier transform infrared spectroscopy. The explanation of the anomalous behavior was given by means of a multiscale approach correlating the microscopic (structural) and macroscopic (compressive strength) properties. In perspective, this finding may be interesting not only from the fundamental materials science point of view, but also for novel applications. For example, it might be utilized as an “intrinsic bioreactor”, playing the role of stimulator of cellular proliferation by exerting stresses due to its alternative contracting and expanding internal forces on the tissues.

Recently, the superhardness of rhenium diboride was discovered. This study presents a first successful preparation and characterization of thin ReB2 films. The films were deposited by the pulsed laser deposition (PLD) technique. The morphology, microstructure, and hardness of the films were investigated. The films are compact and continuous, with a preferred (002) orientation. The composite Vickers hardness of the film-substrate systems was measured, and the intrinsic hardness of the films was separated using an area law-of-mixtures approach taking into account the indentation size effect. The obtained films are found to be superhard: the intrinsic film hardness value (52 GPa) is close to that of the ReB2 bulk.

Calcium phosphate coatings are known to enhance long-term fixation, reliability and promote osteointegration of cementless titanium-based implant devices. This study was aimed at the pulsed laser deposition of calcium phosphate coatings onto titanium using hydroxyapatite and hydroxyapatite-fluorapatite targets. The deposition was carried out at the high laser beam fluence conditions, about 12 J/cm(2). The coatings were characterized with respect to their morphology, phase composition and hardness. X-ray energy dispersive analysis revealed the coatings retain their elemental composition, and fluoride content within the film is the same as in the initial target. However, unlike sintered targets, the deposited films contain no apatite-like phases. The hardness of the films, about 18 GPa, is surprisingly high compared to that of hydroxyapatite and hydroxyapatite-fluorapatite ceramic targets. The deposited coatings of 2.7-2.9 microm thickness have uniform and dense microstructure, containing the solidified droplets of the expulsed from the target phase. The uncommon structure and hardness of the films can be attributed to the melting and phase decomposition of the initial material in the laser plasma.

Hardness of titanium carbide films deposited on silicon (111) substrate by pulsed laser ablation is evaluated in dependence on laser beam fluence and the film thickness. Measurements were performed with the use of a common microhardness testing equipment, the indenter penetartion depth being more than thickness of the coating. Two methods based both on a law-of-mixtures approach were employed to calculate the film hardness from the measured hardness of the composite film-substrate system. One of them accounts for the indentation size effect. The hardness is revealed to reduce significantly with an increase of the film thickness and the laser beam fluence.

In this study, the real-time monitoring of structural changes, occurring upon poorly crystalline apatite bone cement hardening in the presence of chitosan, simulated body fluid and human blood, was performed. Strong experimental evidence of octacalcium phosphate intermediate phase is provided. The energy dispersive X-ray diffraction was applied in situ to monitor the structural changes upon the transformation process, while the Fourier transform infrared spectroscopy and the scanning electron microscopy supplied information on the vibrational and morphological properties of the system. The cooperative action of chitosan and simulated body fluid induces the formation of a preferentially oriented hydroxyapatite phase, this process being similar to the oriented self-assembling process in collagen-apatite matrix in human plasma, occurring upon in vivo biomineralization. Conversely, the presence of blood does not induce any significant change in hardening kinetics and the final structure of the investigated cement.

Carbonated hydroxyapatite (CHA)-coated titanium can find wide applications as bone substitute implant in bone and dental surgery and orthopedics, promoting osseointegration with a host bone and ensuring biocompatibility and bioactivity. In this work, carbonated hydroxyapatite films were prepared on titanium substrates by pulsed laser deposition at different substrate temperatures ranging from 30 to 750 degrees C. The properties of films were investigated by scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray diffraction, and Fourier transform infrared spectroscopy. Vickers microhardness measurements of the composite film-substrate systems were performed, and the intrinsic hardness of films was separated from the composite hardness using a "law-of-mixtures" approach and taking into account the indentation size effect. The prepared CHA films are nearly stoichiometric with a Ca/P atomic ratio of 2.0-2.2. The films deposited in the 30-500 degrees C temperature range are about 9 microm thick, amorphous, having an average roughness of 60 nm. At higher temperature, 700-750 degrees C, the films are about 4 microm thick, show a finer surface morphology and an average roughness of 20 nm. At 750 degrees C the films are amorphous, whereas at 700 degrees C they are crystalline and textured along the (202) and (212) directions. The intrinsic hardness of the films increased with an increase in substrate temperature, being as low as 5 GPa at 30 degrees C and reaching a high value of 28 GPa at 700 degrees C. The rich information gained by the joint use of the mentioned techniques allowed a comprehensive characterization of this system.

Despite the numerous literature data available in the field of calcium phosphate bone cements, the mechanism and kinetics of their hardening, both of which are of great importance for cements application, in most cases, is unknown. In this work, the mechanism and kinetics of hardening of two novel high-strength calcium phosphate bone cements were studied using the energy dispersive X-ray diffraction technique, which allows rapid collection of the patterns. The phase transformations occurring on the setting and hardening processes were monitored in situ. Containing minimal quantity of components, whose mixing leads to the formation of cements with pH close to neutral, the cements under study are simple in handling. The main component of both formulations is tetracalcium phosphate. In both cements, the effect of the addition of high- and low-molecular weight chitosan on phase development and kinetics was investigated in detail. One of the cements has the compressive strength of about 70 MPa, whereas the strength of the other, containing Ca3Al2O6, is much higher, about 100 MPa. This latter cement could be regarded as an alternative to the common low-strength bioresorbable brushite cements. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010

Recently, the superhardness of rhenium diboride was discovered. This study presents a first successful preparation and characterization of thin ReB2 films. The films were deposited by the pulsed laser deposition (PLD) technique. The morphology, microstructure, and hardness of the films were investigated. The films are compact and continuous, with a preferred (002) orientation. The composite Vickers hardness of the film−substrate systems was measured, and the intrinsic hardness of the films was separated using an area law-of-mixtures approach taking into account the indentation size effect. The obtained films are found to be superhard: the intrinsic film hardness value (52 GPa) is close to that of the ReB2 bulk.

A novel approach for preparation of composite materials based on the poly-L-lactide (PL), starch and calcium phosphates is provided, applying the polymer crazing process in liquid absorption active medium. For composite films preparation, PL and blends of PL and starch have been chosen as polymeric matrixes. Pores formation in the polymer films occurred during the process of uniaxial stretching in the presence of ethanol or water-ethanol mixtures via the solvent-crazing mechanism. The diameter of pores and fibrils in crazed PL was 20-30 nm. Porous polymer matrixes have been loaded with starch, using crazing mechanism, and filled with calcium phosphates (CP) by the countercurrent diffusion method, the content of starch and CP being up to 11.0 and 14.5 wt%, respectively. The obtained composites were investigated by XRD, SEM-EDS and TEM methods. It was found out that the starch filled the porous crazed structure of polymer, while the CP synthesis in the PL pores resulted in the formation of amorphous particles with the diameter of about 20 nm. These CP nanoparticles aggregated into the submicron particles of 100-300 nm in diameter. The bioactivity of the initial and porous poly-L-lactide films, and composites, based on PL with starch and calcium phosphates, was investigated. It was shown that the bioactivity depends on the chemical composition and surface morphology of the prepared materials. After 10 days of cultivation of the pre-osteoblastic MC3T3E1 cells, an intense, 6 times, growth of osteoblast population was achieved for the composite containing calcium phosphates. This result is perceptibly higher than those obtained for other samples (4 times growth) and for the control sample (5 times growth). Based on the results of in vitro tests, it can be concluded that the prepared materials are promising for biomedical applications.

The author assess the influence of grain size and temperature on the fracture properties of a zirconium dioxide ceramic and determine that there are at least three effects leading to an increase in crack resistance with the addition of coarse particles to a matrix of fine particles: an increase in the area of the fracture surface; rounding by the crack of the filler particles accompanied by a change in orientation of the crack relative to the direction of action of the maximum tensile stresses; and the formation and development of a zone of energy dissipation ahead of the main crack front. The relative contribution of each of these effects is evaluated.