Bioactivity Features of a Zn-1%Mg-0.1%Dy Alloy Strengthened by Equal-Channel Angular Pressing.

The structure, phase composition, corrosion and mechanical properties, as well as aspects of biocompatibility in vitro and in vivo, of a Zn-1%Mg-0.1%Dy alloy after equal-channel angular pressing (ECAP) were studied. The structure refinement after ECAP leads to the formation of elongated α-Zn grains with a width of ~10 µm and of Mg- and Dy-containing phases. In addition, X-ray diffraction analysis demonstrated that ECAP resulted in the formation of the basal texture in the alloy. These changes in the microstructure and texture lead to an increase in ultimate tensile strength up to 262 ± 7 MPa and ductility up to 5.7 ± 0.2%. ECAP slows down the degradation process, apparently due to the formation of a more homogeneous microstructure. It was found that the alloy degradation rate in vivo after subcutaneous implantation in mice is significantly lower than in vitro ones. ECAP does not impair biocompatibility in vitro and in vivo of the Zn-1%Mg-0.1%Dy alloy. No signs of suppuration, allergic reactions, the formation of visible seals or skin ulcerations were observed after implantation of the alloy. This may indicate the absence of an acute reaction of the animal body to the Zn-1%Mg-0.1%Dy alloy in both states.

Structure, Biodegradation, and In Vitro Bioactivity of Zn-1%Mg Alloy Strengthened by High-Pressure Torsion.

The effect of high-pressure torsion (HPT) on the microstructure, phase composition, mechanical characteristics, degradation rate, and bioactive properties of the Zn-1%Mg alloy is studied. An ultrafine-grained (UFG) structure with an average grain size of α-Zn equal to 890 ± 26 nm and grains and subgrains of the Mg2Zn11 and MgZn2 phases with a size of 50-100 nm are formed after HPT. This UFG structure leads to an increase in the ultimate tensile strength of the alloy by ~3 times with an increase in elongation to 6.3 ± 3.3% due to the formation of a basal texture. The study of corrosion resistance did not show a significant effect of HPT on the degradation rate of the alloy. In addition, no significant changes in the bioactivity of the alloy after HPT: hemolysis, cellular colonization and Escherichia coli growth inhibition.

Structure Optimization of a Fe-Mn-Pd Alloy by Equal-Channel Angular Pressing for Biomedical Use.

In this work, a Fe-Mn-Pd alloy was produced by methods of equal channel angular pressing (ECAP) in order to obtain an alloy with a high rate of degradation for the development of biodegradable devices. Special efforts were made to the obtaining of an ultrafine-grained structure of alloys in a fully austenitic state at temperatures of 300 °C and 450 °C. Further investigation of its effect on the corrosion rate and mechanical properties was carried out. The formation of an austenitic structure with structural element sizes of 100-250 nm after deformation was confirmed by X-ray diffraction analysis. ECAP proved to be the reason for a significant increase in strength with maximum σUTS = 1669 MPa and σYS = 1577 MPa while maintaining satisfactory plasticity. The alloy degradation rate was investigated using the potentiodynamic polarization analysis. The corrosion rate of the alloy after ECAP (~1 mm/y) is higher than that of the coarse-grained state and significantly higher than that of annealed iron (~0.2 mm/y). ECAP in both modes did not impair the biocompatibility of the Fe-Mn-Pd alloy and the colonization of the sample surface by cells.

Effect of Rotary Swaging on the Structure, Mechanical Characteristics and Aging Behavior of Cu-0.5%Cr-0.08%Zr Alloy.

A study of the effect of rotary swaging (RS) on the microstructure and properties of the pre-extruded and pre-quenched Cu-0.5%Cr-0.08%Zr alloy was performed. RS leads to the formation of an ultrafine-grained (UFG) microstructure. UFG structure formation caused by RS increases the ultimate tensile strength (UTS) up to 443 ± 5 MPa and 597 ± 9 MPa for pre-quenched and pre-extruded alloys, respectively. Additionally, the reduction in ductility occurs after RS. It should be noted that UTS is increased for a pre-quenched alloy, while the strength of a pre-extruded alloy is dropped. The growth of UTS for the pre-quenched alloy is associated with the precipitation of fine Cr particles, whereas the recovery processes in the pre-extruded alloy induce the reduction in its UTS. An additional advantage of RS is an increase in the fatigue limit of the pre-quenched alloy up to 265 MPa, and of the pre-extruded alloy up to 345 MPa. The combination of extrusion and RS allows for the increase of the UTS of the Cu-0.5%Cr-0.08%Zr alloy up to 597 ± 9 MPa, while the levels of ductility and electrical conductivity are 10.9 ± 0.9% and 82.0 ± 1.7% IACS, respectively.

Anti-tumour activity of Mg-6%Ag and Mg-10%Gd alloys in mice with inoculated melanoma.

Cytotoxicity in vitro and anti-tumour activity in vivo of magnesium alloys Mg-6%Ag and Mg-10%Gd was studied. It was shown that specifically designed and thermomechanically processed Mg alloys produced a sizeable cytotoxic effect on PC-3 line tumour cells in vitro through inhibition of their proliferation. A pronounced grain refinement in combination with the formation of second phases and precipitates attained by means of equal-channel angular pressing (ECAP) accellerated the degradation and gave rise to enhanced anti-tumour activity of both alloys. The gadolinium-containing alloy outperformed the silver-containing one substantially. In an in vivo assay, intratumoural implantation of pins made from both alloys in the homogenised and the ECAP states in mice with inoculated B16 melanoma gave rise to an indubitable anti-tumour effect. It was documented in a decrease of Ki-67(+) cells and the occurrence of regions of destruction of tumoural tissue that were filled with gas evolving in the course of biodegradation of the implants. The data obtained suggest that intratumoural implantation of gadolinium-containing magnesium alloys can be considered for therapy of inoperable or chemoresistant forms of cancer.

Cytotoxicity of biodegradable magnesium alloy WE43 to tumor cells in vitro: Bioresorbable implants with antitumor activity?

In this study, a degradable magnesium alloy WE43 (Mg-3.56%Y-2.20%Nd-0.47%Zr) was used as a research object. To refine its microstructure from the initial homogenized one, the alloy was subjected to severe plastic deformation (SPD) by equal channel angular pressing (ECAP). The data presented show that coincubation of tumor LNCaP and MDA-MB-231 cells with the WE43 alloy in the homogenized and the ECAP-processed states led to a decrease in their viability and proliferation. An increase in the concentration of Annexin V(+) cells during coincubation with samples in both microstructural states investigated was also observed. This is associated with the induction of apoptosis in the cell culture through contact with the samples. Concurrently, a significant drop in the concentration of Bcl-2(+) cells occurred. It was established that ECAP led to an enhancement of the cytotoxic activity of the alloy against tumor cells. This study demonstrated that alloy WE43 can be considered as a promising candidate for application in orthopedic implants in clinical oncology, where it could play a double role of a mechanically stable, yet bioresorbable, scaffold with local antitumor activity. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 108B:167-173, 2020.

The Effect of Equal-Channel Angular Pressing on the Microstructure, the Mechanical and Corrosion Properties and the Anti-Tumor Activity of Magnesium Alloyed with Silver.

The effect of equal-channel angular pressing (ECAP) on the microstructure, texture, mechanical properties, corrosion resistance and cytotoxicity of two magnesium-silver alloys, Mg-2.0%Ag and Mg-4.0%Ag, was studied. Their average grain size was found to be reduced to 3.2 ± 1.4 µm and 2.8 ± 1.3 µm, respectively. Despite the substantial grain refinement, a drop in the strength characteristics of the alloys was observed, which can be attributed to the formation of inclined basal texture. On a positive side, an increase in tensile ductility to ~34% for Mg-2.0%Ag and ~27% for Mg-4.0%Ag was observed. This effect can be associated with the activity of basal and prismatic slip induced by ECAP. One of the ECAP regimes tested gave rise to a drop in the corrosion resistance of both alloys. An interesting observation was a cytotoxic effect both alloys had on tumor cells in vitro. This effect was accompanied with the release of lactate dehydrogenase, an increase in oxidative stress, coupled with the induction of NO-ions and an increase in the content of such markers of apoptosis as Annexin V and Caspase 3/7. Differences in the chemical composition and the processing history-dependent microstructure of the alloys did not have any significant effect on the magnitude of their antiproliferative effect.

Mechanical Properties, Biodegradation, and Biocompatibility of Ultrafine Grained Magnesium Alloy WE43.

In this work, the effect of an ultrafine-grained (UFG) structure obtained by multiaxial deformation (MAD) on the mechanical properties, fatigue strength, biodegradation, and biocompatibility in vivo of the magnesium alloy WE43 was studied. The grain refinement down to 0.93 ± 0.29 µm and the formation of Mg41Nd5 phase particles with an average size of 0.34 ± 0.21 µm were shown to raise the ultimate tensile strength to 300 MPa. Besides, MAD improved the ductility of the alloy, boosting the total elongation from 9% to 17.2%. An additional positive effect of MAD was an increase in the fatigue strength of the alloy from 90 to 165 MPa. The formation of the UFG structure also reduced the biodegradation rate of the alloy under both in vitro and in vivo conditions. The relative mass loss after six weeks of experiment was 83% and 19% in vitro and 46% and 7% in vivo for the initial and the deformed alloy, respectively. Accumulation of hydrogen and the formation of necrotic masses were observed after implantation of alloy specimens in both conditions. Despite these detrimental phenomena, the desired replacement of the implant and the surrounding cavity with new connective tissue was observed in the areas of implantation.

Microstructure, Microhardness and Corrosion Resistance of WE43 Alloy Based Composites after High-Pressure Torsion.

The structure and properties of a composite consisting of Mg-Y-Nd-Zr alloy (WE43) and various oxides are studied. The particles of the WE43 powder were coated by the nanocrystalline oxide layer by means of a wet chemical deposition process. After that the powder is compressed into solid samples and deformed using high-pressure torsion at room temperature. A second phase is present, both, in pure WE43 alloy and in the one with deposited oxides. We observed that the modification of the alloy by the oxide layer deposition and deformation by high-pressure torsion changes the phase composition and properties of the samples. The samples modified by TiO2 showed the best microhardness and corrosion resistance.

Analysis of the mortality rate among the population of the poltava region and the ways of its reduction.

OBJECTIVE: Introduction: Saving and improvement of population' health is one of the main priorities of the policy in any country. Studying of the level and causes of mortality is a powerful tool for assessing the effectiveness of health care systems. WHO recommends using of the European classification of preventable causes of death that based on three levels of prevention. PATIENTS AND METHODS: The aim of this study is to compare the level and structure of mortality of the population of Ukraine and the Poltava region, to substantiate scientific approaches to the study and identification of those causes of death that can be prevented in order to formulate prevention programs at different level. Materials and methods: In research are used the information from the State Statistics Service of Ukraine and from the Center for Medical Statistics of the MoH of Ukraine. RESULTS: Review: Despite the positive dynamics of mortality in recent years, both in the Poltava region and in Ukraine, the indicators remain extremely negative. About 73.3% of all fatalities in Ukraine are three main types of causes cardiovascular diseases, external causes of death and neoplasms. In the Poltava region, 70.56% of all causes of death are due to cardiovascular disease; neoplasms occupy 13.88%; external causes - 4.87%; diseases of the digestive system - 3,06%; respiratory diseases - 1.31% of the causes of death. CONCLUSION: Conclusions: The mortality rate both in the Poltava region and in Ukraine has tendency for declines, but remains rather high. General trends in the structure of causes of death: in the first place are diseases of the cardiovascular system, the second - neoplasms, the third -external causes. Structuring of the causes of death that based on the principle of prevention in Ukraine do not conduct.