Hank's Solution Research Articles

Comparison of microstructure, mechanical property, and degradation rate of Mg-1Li-1Ca and Mg-4Li-1Ca alloys.

Mg-1 wt.% Li-1 wt.% Ca (LX11) and Mg-4 wt.% Li-1 wt.% Ca (LX41) alloys share the same hexagonal closed-packed crystalline structure. However, the differences in microstructure, mechanical properties, and degradation rates between the two alloys are not well understood. Hereby, the above three aspects of LX11 and LX41 alloys were studied via optical microscopy, tensile tests, and electrochemical polarization and electrochemical impedance spectroscopy, together with hydrogen evolution. The concentration of the released Mg2+, Ca2+, and Li+ ions was analyzed using a flame atomic absorption spectrophotometer. Results demonstrated that the LX11 alloy was composed of finer α-Mg grains, fewer twins, and smaller volume fractions of the intermetallic phases Mg2Ca than the LX41 alloy. The increasing Li concentration generated a weak decrease in the yield strength of the Mg-Li-Ca alloys, a remarkable increase in elongation to failure, and a stable ultimate tensile strength. The LX11 alloy had better corrosion resistance than the LX41 alloy. The release rate of the cations (Mg2+, Ca2+, and Li+) varied significantly with time. The release rate of metallic ions in Hank's solution cannot reflect the true corrosion rate of Mg-Li-Ca alloys due to the formation of the precipitated corrosion products and their difference in solubility. The dealloying corrosion mechanism of the Mg2Ca phase in Mg-Li-Ca alloys was proposed.

Corrosion-tailoring, osteogenic, anti-inflammatory, and antibacterial aspirin-loaded organometallic hydrogel composite coating on biodegradable Zn for orthopedic applications

Zn and its alloys are receiving increasing interest for biodegradable orthopedic implant applications owing to their moderate corrosion rate and the potential functionality of Zn2+. However, their non-uniform corrosion behavior and insufficient osteogenic, anti-inflammatory, and antibacterial properties do not meet the comprehensive requirements of orthopedic implants in clinical use. Herein, an aspirin (an acetylsalicylic acid, ASA, 10, 50, 100, and 500 mg/L)-loaded carboxymethyl chitosan (CMC)/gelatin (Gel)–Zn2+ organometallic hydrogel composite coating (CMC/Gel&Zn2+/ASA) was fabricated on a Zn surface via an alternating dip-coating method, aiming to obtain a material with these comprehensive properties improved. The organometallic hydrogel composite coatings, ca. 12–16 μm in thickness, showed compact, homogeneous, and micro-bulge structured surface morphology. The coatings protected well the Zn substrate from pitting/localized corrosion and contained the release of the bioactive components, Zn2+ and ASA, in a sustained and stable manner in long-term in vitro immersions in Hank's solution. The coated Zn showed greater ability to promote proliferation and osteogenic differentiation for MC3T3-E1 osteoblasts, and better anti-inflammatory capacity when compared with uncoated Zn. Additionally, this coating displayed excellent antibacterial activity against both Escherichia coli (>99 % antibacterial rate) and Staphylococcus aureus (>98 % antibacterial rate). Such appealing properties can be attributed to the compositional nature of the coating, namely the sustained release of Zn2+ and ASA, as well as the surface physiochemical properties because of its unique microstructure. This organometallic hydrogel composite coating can be considered a promising option for the surface modification of biodegradable Zn-based orthopedic implants among others.

Comparison of Elastic and Corrosion Behaviour of Sintered Iron Before and After Its Long Time Immersion in Hank's Solution

Comparison of Elastic and Corrosion Behaviour of Sintered Iron Before and After Its Long Time Immersion in Hank's Solution

Preclinical EIS Study of the Inflammatory Response Evolution of Pure Titanium Implant in Hank's Biological Solution.

Pure titanium (Ti) is investigated in a pre-clinical study in Hank's biological solution using electrochemical methods, open circuit potential, and electrochemical impedance spectroscopy to highlight the time effect in extreme body conditions, such as inflammatory diseases, on degradability due to corrosion processes occurring on the titanium implant. Electrochemical impedance spectroscopy (EIS) data are presented as Nyquist and Bode plots. The results show the increasing reactivity of titanium implants in the presence of hydrogen peroxide, which is an oxygen-reactive compound that describes inflammatory conditions. The polarization resistance, which results from electrochemical impedance spectroscopy measurements, declined dramatically from the highest value registered in Hank's solution to smaller values registered in all solutions when different concentrations of hydrogen peroxide were tested. The EIS analysis provided insights into titanium's in vitro corrosion behavior as an implanted biomaterial, which could not be solely obtained through potentiodynamic polarization testing.

Improving corrosion resistance of pure titanium by simple and controlled oxidation for biomedical applications

AbstractIn this study, the TiO2 passive layer was formed on a pure titanium substrate by simple oxidation in an aqueous solution of H2O2 35 wt.%. In order to determine the appropriate time for the oxidation of the pure titanium substrate, the corrosion rate of the metal in the solution of H2O2 was investigated. The electrochemical behaviour of the TiO2 passive layer on the Ti substrate was investigated in Hank's solution at 37.5°C. The results show that Tafel‐plot extrapolations from the potentiodynamic curves revealed a substantial improvement in the corrosion potentials for the TiO2 coatings. According to the theory calculation, to obtain the optimal surface roughness values, around 100 nm to 300 nm, the oxidation time in H2O2 35 wt.% solution is controlled in the range of 2‐5 hours. The results were explained by considering the effects of crystal morphology and roughness. The results indicated that the controlled oxidation‐prepared TiO2 coatings have attractive prospects for use in biomedical applications since better corrosion protection of pure Ti can be expected.

Corrosion Resistance and Titanium Ion Release of Hybrid Dental Implants.

One of the strategies for the fight against peri-implantitis is the fabrication of titanium dental implants with the part close to the neck without roughness. It is well known that roughness favors osseointegration but hinders the formation of biofilm. Implants with this type of structure are called hybrid dental implants, which sacrifice better coronal osseointegration for a smooth surface that hinders bacterial colonization. In this contribution, we have studied the corrosion resistance and the release of titanium ions to the medium of smooth (L), hybrid (H), and rough (R) dental implants. All implants were identical in design. Roughness was determined with an optical interferometer and residual stresses were determined for each surface by X-ray diffraction using the Bragg-Bentano technique. Corrosion studies were carried out with a Voltalab PGZ301 potentiostat, using Hank's solution as an electrolyte at a temperature of 37 °C. Open-circuit potentials (Eocp), corrosion potential (Ecorr), and current density (icorr) were determined. Implant surfaces were observed by JEOL 5410 scanning electron microscopy. Finally, for each of the different dental implants, the release of ions into Hank's solution at 37 °C at 1, 7, 14, and 30 days of immersion was determined by ICP-MS. The results, as expected, show a higher roughness of R with respect to L and compressive residual stresses of -201.2 MPa and -20.2 MPa, respectively. These differences in residual stresses create a potential difference in the H implant corresponding to Eocp of -186.4 mV higher than for the L and R of -200.9 and -192.2 mV, respectively. The corrosion potentials and current intensity are also higher for the H implants (-223 mV and 0.069 μA/mm2) with respect to the L (-280 mV and 0.014 μA/mm2 and R (-273 mV and 0.019 μA/mm2). Scanning electron microscopy revealed pitting in the interface zone of the H implants and no pitting in the L and R dental implants. The titanium ion release values to the medium are higher in the R implants due to their higher specific surface area compared to the H and L implants. The maximum values obtained are low, not exceeding 6 ppb in 30 days.

In vitro degradation, wear property and biocompatibility of nano-Y2O3-containing micro-arc oxidation coating on ZK60 alloy

In order to further improve the degradation resistance and wear property of micro-arc oxidation (MAO) coating on magnesium alloys, nano-Y2O3 was added into the electrolyte to fabricate a nano-Y2O3-containing MAO coating. Microstructural characterization, wear test, electrochemical test, immersion test and cytotoxicity test were carried out. The results showed that there were mainly Ca8MgY(PO4)7 and Y2O3 particles in the MAO coating. Ca8MgY(PO4)7 could stabilize the coating and the nano-Y2O3 could seal the micro-pores. Therefore, both the degradation resistance and wear property of the coating were improved. The degradation rate decreased from 0.14 to 0.06 mm/a in Hank's solution. The volume loss decreased from 0.46 to 0.27 mm3 at the same slip distance. MAO coating exhibited good biocompatibility with the cell relative growth rate (RGR) value of more than 90%. The nano-Y2O3-containing MAO coating thus has a good promising biomedical application.

Synergistic Effects of Cerium and Hot Forging on Biodegradation, Antibacterial Properties, and In Vivo Biocompatibility of Microalloyed Mg-Zr-Sr Alloys.

Biodegradable magnesium (Mg)-based alloys are potential candidates for orthopedic applications. In the present study, we have discussed the effect of cerium (Ce) addition and hot forging on mechanical properties, in vitro-in vivo corrosion, antibacterial activity, and cytocompatibility of microalloyed Mg-0.2Zr-0.1Sr-xCe (x = 0 [MZS], 0.5 wt % [MZS-Ce]) alloys. Addition of 0.5 wt % Ce to forged MZS alloys leads to strengthening of the basal texture as well as formation of a higher fraction of dynamic recrystallized (DRX) grains. Hot forging and addition of cerium to the MZS alloy improve both the yield strength and ultimate tensile strength of the forged MZS-Ce alloy by 1.39 and 1.21 times, respectively, compared to those of the forged MZS alloy. The potentiodynamic polarization test in Hank's solution indicates that the corrosion resistance of the forged MZS alloy improves with addition of 0.5 wt % Ce. Uniform distribution of Mg12Ce precipitates, a higher DRX fraction, strengthened texture, and formation of a compact CeO2 passive layer result in 1.68 times reduction in the immersion corrosion rate of the forged MZS-Ce alloy compared to that of the forged MZS alloy. Addition of Ce to the MZS alloy shows excellent antibacterial activity. The forged MZS-Ce alloy exhibited the highest antibacterial efficacy (76.73%). All the alloys show favorable cytocompatibility and alkaline phosphatase (ALP) activity with MC3T3-E1 cells. The improved corrosion resistance of the forged MZS-Ce alloy (95%) leads to higher cell viability compared to that of the forged MZS alloy (85%). In vivo biodegradation and the ability to generate new bones were analyzed by implanting cylindrical samples in the rabbit femur. Histological analysis showed no adverse effects around the implants. Gradual degradation of the implants and higher new bone formation around the forged MZS-Ce sample were confirmed by micro-CT analysis. Bone regeneration around the implants (58.21%) was validated by flurochrome labeling. After 60 days, the forged MZS-Ce alloy showed controlled corrosion and better bone-implant integration, presenting it as a potential candidate for internal fracture fixation materials.

The enhancement of mechanical properties and uniform degradation of electrodeposited Fe-Zn alloys by multilayered design for biodegradable stent applications.

Pure Fe is a potential biodegradable stent material due to its better biocompatibility and mechanical properties, but its degradation rate needs to be improved. Alloying with Zn to form Fe-Zn alloy is anticipated to meet the degradation rate requirements while retaining the iron's inherent properties. Therefore, Fe-Zn alloys with monolayered and multilayered structures were prepared by electrodeposition. The alloys' composition, microstructure, mechanical properties, in vitro degradation and biocompatibility were assessed. Results showed that the Zn content ranged from 2.1 wt% to 11.6 wt%. After annealing at 450°C, all the alloys consisted of α(Fe) solid solution and Zn-rich B2 ordered coherent phase, except for the alloy with 11.6 wt% Zn content, in which a Fe3Zn10 phase appeared. The layered structure consisted of alternating columnar-grain and nano-grain layers, which compensated for the intrinsic brittleness of electrodeposited metals and improved the galvanic effect of the alloy, thus increasing the strength and plasticity and changing the corrosion from localized to uniform while augmenting the corrosion rate. The yield strength of the multilayered alloy exceeded 350 MPa, its elongation was more than 20%, and its corrosion rate obtained by immersion test in Hank's solution reached 0.367 mm·y-1. Fe-Zn alloys with lower Zn content had good cytocompatibility with the human umbilical vein endothelial cells and good blood compatibility. The above results verified that the multilayered Fe-Zn alloy prepared by electrodeposition presented enhanced mechanical properties, higher degradation rate, uniform degradation mechanism and good biocompatibility. It should be qualified for the application of biodegradable stents. STATEMENT OF SIGNIFICANCE: A potential biodegradable Fe-Zn alloy, which is difficult to be obtained by the metallurgical method, was prepared by electrodeposition to solve the low degradation rate of iron-based biomaterials. A multilayered microstructure design composed of alternating columnar-grain and nano-grain layers was achieved by changing the electrical parameters. The layered design compensated for the intrinsic poor plasticity of electrodeposited metals. It increased the galvanic effect of the alloy, thus augmenting the corrosion rate and changing the corrosion mode of the alloy from localized to uniform corrosion. The yield strength of multilayered alloy exceeded 350 MPa; its elongation was more than 20%. Moreover, the layered alloy had good cytocompatibility and blood compatibility. It indicates that the alloy is qualified for biodegradable stent application.

The effect of small additions of Nb and Ti on the sliding wear behavior of a Co–30Cr–5Mo alloy

This work studies the addition of 0.5%Nb and 0.5%Ti in a Co–30Cr–5Mo alloy as well as the increase of carbon from 0.1 to 0.3%. The main goal is to increase the wear resistance of the alloy with such additions due to the formation of primary carbides (TiC and NbC). The additions of carbon, niobium and titanium were as ferroalloys, which implies the addition of iron into the chemistry of the alloy. Microstructural prediction studies by JMatPro indicate that the addition of all of these elements promotes an increase in the amount of the sigma phase, an undesirable phase because it is a hard brittle intermetallic compound. However, this undesirable phase could be eliminated from the structure by means of a solubilization heat treatment undertaken at 1200 °C for 2 h; this heat treatment lowered the values of hardness of the alloys. An additional aging heat treatment promoted the precipitation of chromium carbides of the type M23C6 as dispersed elongated bars within the cobalt matrix, which notably increased the hardness of the alloys. Each alloy was wear tested under two loads 52 and 78 N and under dry sliding and also under lubricated sliding using Hank solution as lubricant; the tests were undertaken at a sliding speed of 0.5 m/s. Results indicate that the addition of Ti and Nb produced small amounts of TiC and NbC in addition to a light increase in the amount of the sigma phase which increased hardness in the as-cast conditions. These alloys, with Ti and Nb additions, shown the higher hardness values in the as-aged conditions. The wear resistance of the alloys are in agreement with the hardness results particularly for the dry sliding tests. Wear resistance was higher for the harder alloys (those with Nb and Ti additions in the as-aged conditions) and it is lower for the higher applied load. For the case of the lubricated wear tests, such a trend is also observed but not so clearly as for the unlubricated tests. However, friction and wear for the lubricated experiments shown values extremely low compared to these observed for the unlubricated sliding wear tests.

Microstructural Analysis and Corrosion Behavior of a Titanium Cenosphere Composite Foam Fabricated by Powder Metallurgy Route

AbstractThis study examines the influence of cenosphere particle size and sintering parameters on the microstructure and electrochemical behavior of Ti‐cenosphere composite foam fabricated by powder metallurgy route. Cenosphere has been added as a space holder material to develop Ti composite foam because of its abundant availability and low cost. Ti (particle size between 250 μm and 350 μm) and cenosphere (with a varying particle size of <150 μm, 150 μm–200 μm and >200 μm) in the ratio of 75 : 25 (wt %) were compacted using 100 MPa of applied pressure and sintering temperatures of 1000 and 1200 °C with sintering time ranging from 2 to 6 h at a heating rate of 25 °C/min. A defect‐free microstructure with the uniform dispersion of cenosphere particles in the Ti matrix was observed with the cenosphere particles in the size range of 150–212 μm at a sintering temperature of 1000 °C for 4 h. The porosity content in the syntactic foam varied from 34 to 50 % and decreased with increasing sintering time and temperature. Based on a detailed study of corrosion behavior in Hank's solution, the composite foam with cenosphere particles in the size range of 150–212 μm and sintered at 1000 °C for 4 h showed the highest corrosion resistance.

Polypyrrole/zinc bilayer coating on ZK60 magnesium alloy for enhanced corrosion protection in Hank's solution

A polypyrrole/zinc (PPy/Zn) bilayer coating is prepared to significantly improve the corrosion resistance of ZK60 magnesium alloy in 37 °C Hank's solution to meet the requirements for biodegradable metals. The zinc coating composed of dense and uniform flake-like zinc crystals displays good abrasion resistance and adhesion strength, acting as a vital intermediate layer for growing the PPy film doping with tartrate anions (TA−). The prepared PPy/TA films (10, 20 and 28 μm) on the Zn coating are compact and have high stability in Hank's solution. The electrochemical and hydrogen evolution tests for PPy/Zn/ZK60 specimens show that the PPy/TA film's stability determines the protective performance of PPy/Zn coating in a long immersion period. The PPy(20 μm)/Zn coating has the longest protection time (40 ± 4 days), and too thick PPy film (28 μm) damages its structure to accelerate breakage, developing local corrosion quickly on ZK60. The corrosion mechanism involved is discussed.

Tribocorrosion-Resistant Surface for TiO2 as a Function of Load and Sliding Speed

The applications projected in the coatings are in implants with the lower extremities since they require a great load capacity and are essential for walking. Therefore, the use of devices or implants is necessary for recovery, osteosynthesis, and fixation. The tribocorrosive behavior of nanostructured compounds based on titanium oxide with an intermediate layer of gold deposited on titanium substrates was determined. These coatings were obtained using the reactive magnetron sputtering technique. Tribocorrosive properties were evaluated at sliding speeds of 3500 mm/min, 4500 mm/min, 6000 mm/min, 7500 mm/min, and 9000 mm/min with loads of 1 N, 2 N, 3 N, 4 N, and 5 N. The coatings were characterized by X-ray photoemission spectroscopy and X-ray diffraction, and the surface roughness was analyzed by atomic force microscopy. The dual mechanical and electrochemical wear tests were carried out with a potentiostat coupled to a pin on the disk system. The system was in contact with a hanks solution (37 °C), which acted as a lubricant. Structural characterization made it possible to identify the TiO2 compound. In the morphological characterization, it was found that the substrate influenced the surface properties of the coatings. The tribological behavior estimated by the wear rates showed less wear at higher load and sliding speeds. It was shown that it is possible to obtain coatings with better electrochemical and tribological performance by controlling the applied load and slip speed variables. In this study, a significant decrease corresponding to 64% was obtained, specifically in the speed of deterioration, and especially for a load of 5 N, depending on the sliding speed that went from 0.2831 mpy (Mils penetration per year) to 3500 mm/min compared to 0.1045 mpy at 9000 mm/min, which is explained by the mechanical blockage induced by the coating.

A novel biodegradable high nitrogen iron alloy with simultaneous enhancement of corrosion rate and local corrosion resistance

To improve the corrosion rate and suppress the local corrosion, a novel biodegradable high nitrogen (N) FeMnN alloy was developed, and the effects of N content on the corrosion behaviors were systematically investigated. It was found that, as the N content increased, the corrosion rate was significantly enhanced in both Hank's solution and simulated gastric fluid. Meanwhile, as the N content increased, the size and depth of pits decreased obviously, and the number of pits increased, which presented a more uniform corrosion morphology. X-ray photoelectron spectroscopy (XPS) results indicated that N existed in the form of NH4+ in the corrosion products and [FeN] clusters in the matrix. The [FeN] clusters would simultaneously improve the corrosion rate and suppress the local corrosion, which provides a new perspective for the development of biodegradable Fe alloy.

Effects of thermomechanical processing on microstructures, mechanical properties, and biodegradation behaviour of dilute Zn–Mg alloys

Currently, zinc has been considered as one new attractive biodegradable metal for medical implant applications due to its favoured properties such as biocompatibility and recyclability. However, the cast pure zinc usually possesses coarsening microstructures, which hinders it to obtain a suitable combination of mechanical strength and degradation rate. Here, the microstructural controlling of zinc was firstly realized via alloying dilute Mg contents and thermomechanical processing. Then, the in vitro biodegradation behaviour of dilute Zn–Mg alloys was investigated accordingly using the Hank's solution. Finally, the mechanisms of mechanical strengthening and in vitro biodegradation were explored. Specifically, the Mg-50wt%Zn master alloy was added into cast Zn melt to form the binary Zn–Mg alloys with different Mg addition contents (i.e. 0, 0.05wt%, 0.1wt%, and 0.4wt%). The initial reduction of grain sizes was achieved by over 90% owing to the grain refinement generated by master alloy. In the as-cast alloys, the average grain size was decreased from over 2 mm for pure Zn to 23.7 μm for Zn-0.4wt%Mg. Subsequently, the thermomechanical processing (i.e. hot rolling at room temperature, 100°C, 150°C, and 250°C) was applied onto the cast Zn–Mg alloys to achieve further microstructural manipulation. Further grain refinement occurred in the different as-rolled Zn–Mg alloys. The in vitro corrosion resistance of all samples was assessed through the potentiodynamic polarization (PDP) test in the Hanks' solution for 14 days at 37°C. The corrosion rates depended on alloying contents, grain sizes, twins and texture. The synergetic regulation of mechanical strength and degradation rate could be adjusted by appropriately using master alloys and thermomechanical processing. For practical medical applications, the present work provides some insights on solving the dilemma between mechanical properties and biodegradation process.

Enhancing mechanical properties and degradation performance of Mg−0.8wt.%Ca alloy by directional solidification

The mechanical properties and degradation performance in Hank's solution of the directionally solidified (DSed) Mg−0.8Ca (wt.%) alloys were investigated and compared with those of the as-cast alloy. The microstructure was studied by OM, SEM, TEM, and EBSD. It is found that the columnar grains in DSed alloys have a consistent growth orientation of <1120>. The mechanical strength and ductility of Mg−0.8Ca alloy are significantly improved after directional solidification. Besides, the corrosion resistance of Mg−0.8Ca alloy in Hank's solution is dramatically enhanced after directional solidification. The Mg−0.8Ca alloys in Hank's solution mainly undergo microgalvanic corrosion, and the corrosion products consist of Mg(OH)2, (Ca, Mg)3(PO4)2, and hydroxyapatite (HA). The superior properties of the DSed Mg−Ca alloy are beneficial from the columnar microstructure and the redistribution of the eutectics. The DSed Mg−0.8Ca alloy with columnar dendritic structure is expected to be used as biodegradable materials.

Effect of Implantoplasty on Roughness, Fatigue and Corrosion Behavior of Narrow Diameter Dental Implants.

Implantoplasty (IP) is used in dental implants with peri-implantitis and aims to remove threads and polish rough surfaces in order to prevent bacterial colonization. As a result of this procedure, implant strength might be compromised. We tested 20 tapered screw-shaped Ti6Al4V dental implants with a simulated bone loss of 50%. Ten implants underwent IP and 10 served as controls. Surface topography (Sa, Sz, Ssk, and Sdr) was analyzed with a confocal optical microscope. Subsequently, a minimum of four series of cyclic loads were applied with a servo-hydraulic mechanical testing machine (5 × 106 cycles at 15 Hz, between a maximal nominal value-starting at 529 N in the IP group and 735 N in the control group-and 10% of that force). We recorded the number of cycles until failure and the type of failure. Implant failure was analyzed by visual inspection and scanning electron microscopy. Open circuit potential and potenctiodynamic tests were carried out with high precision potentiostat using Hank's solution at 37 °C to evaluate the effect of the implantoplasty on the corrosion resistance. Implantoplasty significantly reduced the surface topography values (median) and interquartile range (IQR); Sa from 1.76 (IQR = 0.11) to 0.49 (IQR = 0.16), Sz from 20.98 (IQR = 8.14) to 8.19 (IQR = 4.16), Ssk from 0.01 (IQR = 0.34) to -0.74 (IQR = 0.53) and Sdr from 18.20 (IQR = 2.26) to 2.67 (IQR = 0.87). The fatigue limits of the control and implantoplasty groups were 551 N and 529 N, respectively. The scanning electron micrographs showed fatigue striations indicating fatigue failure. Besides, the fractographic analysis revealed a typical brittle intergranular fracture mechanism. The infinite life range of the dental implants evaluated was largely above the threshold of usual chewing forces. Implantoplasty seems to render a fairly smooth surface and has a limited impact on fatigue resistance. In addition, implantoplasty produces a decrease in the corrosion resistance of the implant. Corrosion current density from 0.019 μA/cm2 for as-received to 0.069 μA/cm2 in the interface smooth-roughened dental implant. These places between the machining and the rough area of the implant are the most susceptible, with the appearance of pitting.

Degradation behavior, biocompatibility and antibacterial activity of plasma electrolytic oxidation treated zinc substrates

A ZnO/Zn(OH)2 hybrid coating was fabricated in situ via plasma electrolytic oxidation (PEO) in Na2CO3 electrolyte on pure Zn surface for elucidating the influence of PEO treatment on the degradation behavior of Zn and Zn-based materials. Degradation effects, including surface morphology evolution, corrosion product generation and degradation rate, were systematically investigated through simulated body fluid (SBF) immersion and Hank's solution immersion tests. The results confirm that PEO treatment accelerates the degradation of Zn. With the rise in applied voltage, the initial degradation rate decreases from 0.60 to 0.20 mm/year, whereas the long-term degradation rate can reach 0.50–0.70 mm/year. Especially, the degradation rate acquired at 400 V could meet the general design criteria for degradation rate of biodegradable metallic devices. The corrosion products mainly consist of Zn(OH)2, ZnO, Zn3(PO4)2 and CaP matters. They aggregate to form a bi-layer on the as-formed PEO coating surface. Furthermore, the good in vitro biocompatibility and antibacterial properties of the PEO-treated Zn indicate that PEO is a promising method to treat Zn and Zn-based implants for orthopedic application. When the applied voltage is 400 V, the increased hydrophilicity (WCA <25°), good biocompatibility (cell viability >100 %) and the best enhanced antibacterial performance (53.3 % for S. aureus, 88.3 % for E. coli) compared to that of pure Zn are observed.

ГИДРОКСИПИРИДИНА АСКОРБИНАТ ПОВЫШАЕТ ВЫЖИВАЕМОСТЬ НЕЙРОНОВ ГОЛОВНОГО МОЗГА

In this work, the cytoprotective effect of the original substance 3-hydroxypyridine ascorbate (3-EA) was studied. Cells for mixed cortical neuroglial culture were isolated from the brain (GM) of neonatal NMRI mice. The cell density in culture was adjusted to 15000 cells per 1 cm2. For experiments, 10-day-old cultures were used. To register the intracellular concentration of calcium ions ([Ca2+]i), cells were loaded with an intracellular fluorescent probe Fura-2AM dissolved in Hanks solution at a concentration of 4 μM, followed by 40-minute incubation at a temperature of 370C. Cells were washed three times before the experiment. Potassium chloride was applied to identify neurons, and short-term addition of ATP to the medium was used to detect glial cells (astrocytes). Cell cultures of the mouse cerebral cortex were preincubated for 24 hours with various concentrations (10, 50 and 100 μM) of 3-EA. The amplitude and shape of calcium responses were determined under conditions of oxygen-glucose deprivation (oxygen-glucose deprivation, OGD) and glutamatergic excitotoxicity (GluTox). Using fluorescence microscopy, cell viability tests, and PCR analysis, 3-EA has been shown to dose-dependently inhibit cortical cell death under glutamate excitotoxicity and ischemia/reoxygenation. Preincubation of cerebral cortex cells with 3-EA in the concentration range of 10–100 μM leads to a significant inhibition of the increase in Ca2+ ions in the cytosol ([Ca2+]i) of neurons and astrocytes in modeling glutamate excitotoxicity (GluTox) and oxygen-glucose deprivation (OGD). Decreasing [Ca2+]i and establishing a lower baseline [Ca2+]i inhibits necrotic cell death in an acute experiment.

Using high pressure torsion to process magnesium alloys for biological applications

The effect of high pressure torsion processing on mechanical properties and corrosion behavior of pure magnesium and Mg-Zn, Mg-Zn-Ca, Mg-Li-Y and Mg-Y-RE alloys is investigated. Micro-tomography and SEM characterization are used to estimate corrosion rate and evaluate non-uniform corrosion features. The results show that severe plastic deformation processing improves the strength of all magnesium alloys, but deformation localization can take place in the Mg-Zn-Ca and Mg-Y-RE alloys. The occurrence of deformation localization is associated with low strain rate sensitivity in these alloys and with severe corrosion localization. Pure magnesium and Mg-Zn and Mg-Li-Y alloys display good corrosion resistance with a low corrosion rate and maintain integrity after 28 days of immersion in Hank's solution.