Search

Additively manufactured biodegradable zinc (Zn) alloy scaffolds constitute an important branch in orthopedic implants because of their moderate degradation behavior and bone-mimicking mechanical properties. This work investigated the corrosion fatigue response of a zinc-magnesium (Zn-Mg) alloy gyroid scaffold fabricated via laser-powder-bed-fusion additive manufacturing at the first time. The high-cycle compression-compression fatigue testing of the printed Zn-Mg scaffold was conducted in simulated body fluid, showing its favorable fatigue strength, structural reliability, and anti-fatigue capability. The printed Zn-Mg scaffold obtained a 227% higher fatigue strength than that of the printed Zn scaffold but 17% lower strain accumulation at 10 6 cycles. The accumulative strain of the Zn-Mg scaffold at its fatigue strength was dominant by fatigue ratcheting, since the fatigue damage strain of the scaffold was approximately zero. The corrosion products (ZnO and Zn(OH) 2 ) were conducive to the inhibition of fatigue ratcheting and fatigue damage. Dislocation pile-up and solid solution phases at the grain boundaries of the Zn-Mg scaffold could retard the spreading of the crack tip and impede excessive grain coarsening, improving its fatigue endurance limit. Notably, the printed Zn-Mg scaffold could dissipate the fatigue energy through moderate grain boundary migration, thus reducing its plastic deformation. These findings illuminated the anti-fatigue mechanisms related to microstructural features and corrosive environments and highlighted the promising prospects of additively manufactured Zn-Mg scaffolds in orthopedic applications. STATEMENT OF SIGNIFICANCE: Additive manufacturing (AM) of biodegradable metals shows unprecedented prospects for bone tissue regeneration medicine. The corrosion fatigue property is one of the key determinants in the performance of AM biodegradable scaffolds. In this study, a Zn-Mg gyroid scaffold was additively manufactured with admirable fatigue endurance limit and anti-fatigue capability. We reported that the corrosion fatigue performance was highly relevant to the microstructural features, validating that the grain boundary engineering strategy improved fatigue strength and inhibited crack penetration. Notably, moderate grain boundary migration could dissipate fatigue energy and reduce plastic deformation. Furthermore, corrosion products were conducive to impeding fatigue ratcheting and fatigue damage, indicating the promising potential of AM Zn-Mg scaffolds in treating load-bearing bone defects., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Background: The quantitative association between serum/dietary magnesium and cardiovascular disease (CVD) remains unclear. We conducted a dose-response meta-analysis to evaluate the quantitative association between serum/dietary magnesium and CVD, including coronary heart disease (CHD)., Methods: PubMed, China National Knowledge Infrastructure, and Web of Science were searched for publications. STATA 12.0 was used to analyze data. We used the random-effects model to reduce heterogeneity., Results: Eighteen prospective cohort studies with 544,581 participants and 22,658 CVD cases were included. The follow-up duration was 1-28 years. The pooled relative risk (RR) of CVD for the relatively normal versus lowest serum and dietary magnesium level was 0.64 {[95% confidence interval (CI): 0.51-0.80] and 0.90 [95% CI: 0.84-0.96]}. The pooled RR of CHD for the relatively normal versus lowest serum and dietary magnesium level was 0.70 (95% CI: 0.57-0.85) and 0.86 (95% CI: 0.77-0.94). We noted a significant association between increasing serum magnesium levels (per 0.1-mg/dL increase) and risk of CVD (RR: 0.93, 95% CI: 0.88-0.97) and CHD (RR: 0.90, 95% CI: 0.84-0.96) and between dietary magnesium levels (per 100-mg/d increase) and risk of CVD (RR: 0.90, 95% CI: 0.83-0.96) and CHD (RR: 0.92, 95% CI: 0.82-0.98). Serum/dietary Mg level comparisons presented a 7%-10% decrease in CVD/CHD risk. The dose-response meta-analyses showed linear relationships between serum magnesium and CVD (Pnonlinearity = 0.833) or CHD (Pnonlinearity = 0.193) and dietary magnesium and CVD (Pnonlinearity = 0.463) or CHD (Pnonlinearity = 0.440)., Conclusions: Increasing dietary magnesium or serum magnesium level is linearly and inversely associated with the risk of total CVD and CHD events.

Background and Objectives: Hearing loss is a sensory impairment caused by genetic and environmental factors. Previous epidemiological studies of magnesium intake and hearing loss have yielded conflicting results., Methods and Study Design: We investigated the association between serum magnesium concentrations and hearing loss in a population from the Zhejiang region of China. A cross-sectional study of 3,267 participants aged 18 years and older from five hospitals was conducted from October 2016 to May 2018. An audiometric examination was conducted, and hearing thresholds were computed as pure-tone averages (PTAs) at speech (0.5, 1, 2, and 4 kHz) and high frequencies (3, 4, and 6 kHz). Magnesium concentrations were measured using an inductively coupled plasma mass spectrometer., Results: A linear regression analysis revealed a negative association between magnesium levels and hearing losses from lower to high PTAs. After the adjustment of potential confounders, participants in the highest magnesium quartile had a lower PTA (quartile 4: -1.89%; 95% confidence interval (CI: -3.07 to -0.701); p=0.022) and high PTA (quartile 4: -3.05%; 95% CI: -4.64 to -1.46; p=0.005) than those in the lowest quartile. A logistic regression analysis showed a dose-dependent reduction in the odds of high frequency hearing loss across magnesium quartiles. In model 3, after adjusting for all potential confounders, participants with the highest magnesium quartiles had a 54.0% (OR: 0.460; 95% CI: 0.339-0.587) reduction in the odds of high-frequency hearing loss., Conclusions: Higher whole blood levels of magnesium in this population were associated with lower hearing thresholds and risk of hearing loss.

Rare earth element Dy is one of the promising alloying elements for magnesium alloy as biodegradable implants. To understand the effect of Dy in solid solution on the degradation of Mg-Dy alloys in simulated physiological conditions, the present work studied the microstructure and degradation behavior of Mg-Dy alloys in cell culture medium. It is found the corrosion resistance enhances with the increase of Dy content in solid solution in Mg. This can be attributed to the formation of a relatively more corrosion resistant Dy-enriched film which decreases the anodic dissolution of Mg., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Surface modification techniques have been applied to generate titanium implant surfaces that promote osseointegration for the implants in cementless arthroplasty. However, its effect is not sufficient for osteoporotic bone. Zinc (Zn), magnesium (Mg), and strontium (Sr) present a beneficial effect on bone growth, and positively affect bone regeneration. The aim of this study was to confirm the different effects of the fixation strength of Zn, Mg, Sr-substituted hydroxyapatite-coated (Zn-HA-coated, Mg-HA-coated, Sr-HA-coated) titanium implants via electrochemical deposition in the osteoporotic condition. Female Sprague-Dawley rats were used for this study. Twelve weeks after bilateral ovariectomy, all animals were randomly divided into four groups: group HA; group Zn-HA; group Mg-HA and group Sr-HA. Afterwards, all rats from groups HA, Zn-HA, Mg-HA and Sr-HA received implants with hydroxyapatite containing 0%, 10% Zn ions, 10% Mg ions, and 10% Sr ions. Implants were inserted bilaterally in all animals until death at 12 weeks. The bilateral femurs of rats were harvested for evaluation. All treatment groups increased new bone formation around the surface of titanium rods and push-out force; group Sr-HA showed the strongest effects on new bone formation and biomechanical strength. Additionally, there are significant differences in bone formation and push-out force was observed between groups Zn-HA and Mg-HA. This finding suggests that Zn, Mg, Sr-substituted hydroxyapatite coatings can improve implant osseointegration, and the 10% Sr coating exhibited the best properties for implant osseointegration among the tested coatings in osteoporosis rats., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Hip-preserving surgery with vascularized bone graft implantation has been widely practiced in treating osteonecrosis of the femoral head (ONFH). However, the current approach presents a drawback, in which the implanted bone graft without screw fixation may slip or exhibit a certain degree of displacement postoperatively. This study was designed to investigate the application potential of biodegradable magnesium (Mg) screws for the fixation of vascularized bone graft in ONFH patients. Forty-eight patients were randomly divided into two groups: the Mg screw group (vascularized bone grafting fixed by Mg screws) and the control group (vascularized bone grafting without fixation). During 12 month follow-up period after surgery, treatment outcomes in patients were assessed by multiple imaging techniques including x-ray and computed tomography (CT) scanning as well as functional recovery Harris hip score (HHS). The temporal changes in serum levels of Mg, Ca, and P as well as in vivo degradation rate of Mg screws were determined. The absence of potential adverse effects induced by degradation products from Mg screws on surrounding bone tissue was validated via CT imaging analysis. HHS was significantly improved in the Mg screw group when compared to the control group. X-ray imaging analysis showed that the screw shape did not show significant alteration due to the diameter of Mg screws measured with approximate 25% reduction within 12 months post-surgically. The postoperative serum levels of Ca, Mg, and P, which are relevant for liver and kidney function, were all within normal physiological range in all patients of both groups. The use of biodegradable Mg screws may provide a promising bone graft-screw fixation route in treating ONFH and present considerable potential for orthopedic applications., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Although Mg(2+) is essential for a myriad of cellular processes, high levels of Mg(2+) in the environment, such as those found in serpentine soils, become toxic to plants. In this study, we identified two calcineurin B-like (CBL) proteins, CBL2 and CBL3, as key regulators for plant growth under high-Mg conditions. The Arabidopsis mutant lacking both CBL2 and CBL3 displayed severe growth retardation in the presence of excess Mg(2+), implying elevated Mg(2+) toxicity in these plants. Unexpectedly, the cbl2 cbl3 mutant plants retained lower Mg content than wild-type plants under either normal or high-Mg conditions, suggesting that CBL2 and CBL3 may be required for vacuolar Mg(2+) sequestration. Indeed, patch-clamp analysis showed that the cbl2 cbl3 mutant exhibited reduced Mg(2+) influx into the vacuole. We further identified four CBL-interacting protein kinases (CIPKs), CIPK3, -9, -23, and -26, as functionally overlapping components downstream of CBL2/3 in the signaling pathway that facilitates Mg(2+) homeostasis. The cipk3 cipk9 cipk23 cipk26 quadruple mutant, like the cbl2 cbl3 double mutant, was hypersensitive to high-Mg conditions; furthermore, CIPK3/9/23/26 physically interacted with CBL2/3 at the vacuolar membrane. Our results thus provide evidence that CBL2/3 and CIPK3/9/23/26 constitute a multivalent interacting network that regulates the vacuolar sequestration of Mg(2+), thereby protecting plants from Mg(2+) toxicity.

Magnesium (Mg2+) is an essential metal for plant growth; however, its over‐accumulation in cells can be cytotoxic. The metal tolerance protein family (MTP) belongs to an ubiquitous family of cation diffusion facilitator (CDF) proteins that export divalent metal cations for metal homeostasis and tolerance in all organisms. We describe here the identification of MTP10 to be critical for xylem Mg homeostasis in Arabidopsis under high Mg2+ conditions. The Arabidopsis plant contains 12 MTP genes, and only knockout of MTP10 decreased the tolerance of high‐Mg stress. The functional complementation assays in a Mg2+ ‐uptake‐deficient bacterial strain MM281 confirmed that MTP10 conducted Mg2+ transport. MTP10 is localized to the plasma membrane of parenchyma cells around the xylem. Reciprocal grafting analysis further demonstrated that MTP10 functions in the shoot to determine the shoot growth phenotypes under high Mg2+ conditions. Moreover, compared to the wild type, the mtp10 mutant accumulated more Mg2+ in xylem sap under high‐Mg stress. This study reveals that MTP10 facilitates Mg2+ diffusion from the xylem to shoots and thus determines Mg homeostasis in shoot vascular tissues during high‐Mg stress. [ABSTRACT FROM AUTHOR]

In the present study, to understand the mechanism of Mn on inhibiting Fe-caused Mg corrosion, the corrosion behaviour of commercial pure Mg and Mg-6Mn alloy in 0.6 M NaCl solution is investigated. It is found that in Mg-6Mn alloy, Fe impurity is incorporated into Mn to form Mn (Fe) phase with Fe as solid solute. The initial galvanic corrosion cannot be reduced through converting Fe-rich phase to Mn (Fe) phase, since Mn (Fe) phase also has relatively strong cathodic activity and has much larger volume fraction than Fe-rich phase. However, the cathodic activation behaviour of pure Mg is inhibited. The cathodic activity even decreases for Mg-Mn alloy with increased exposure time, due to the reduced cathodic HER at the Mn (Fe) particles. Mn can be oxidized at the OCP of Mg-6Mn alloy, resulting in relatively dense Mn-rich corrosion film on particle surface, which separates the particle from the electrolyte and, consequently, inhibits HER. [ABSTRACT FROM AUTHOR]

Abstract The hydrated magnesium-carbon films fabricated in this study demonstrated that grain growth and crystallinity modification by substrate temperature treatment crystallization produce films with fewer internal imperfections. This results in high mobility of the solution-deposited hydrated magnesium-carbon electrical conductance, with a corresponding dramatic harmonious transmittance in the infrared range. An investigation of the hydrated magnesium-carbon films shows that the temperature treatment dramatically improves the electron mobility and decreases the carrier concentration, which in turn simultaneously increases the conductivity and transparency. The hydrated magnesium-carbon films exhibit a mobility of up to 85.2 cm2/(V·s) and the resistivity declines rapidly to 1.72 × 10−2 Ω·cm. The transmittance of the visible spectrum increased to 90%. Although the conductivity of hydrated magnesium-carbon films is not prominent comparing to the conventional and widely-used n-type TCO materials, e.g. ITO, the films also showed excellent optical properties, which can be attributed to their low bond energy, with the infrared transmittance of the films being greater than 70% for a plasma wavelength of approximately 10 μm. Graphical abstract Unlabelled Image Highlights • The hydrated magnesium-carbon films are the non-oxide-type transparent electronic material. • The plasma wavelength of hydrated magnesium-carbon films was approximate 10 μm. • Discussed the effects of the carrier concentration and mobility on the photoelectrical properties. • Studied on effects of the substrate temperature on the photoelectrical properties. [ABSTRACT FROM AUTHOR]

The present work investigates the corrosion behaviour of magnesium with different Fe contents. It is found that the micro-galvanic coupling between Fe-rich particles and magnesium matrix results in surface film formation and decrease in anodic reaction rate, consequently, increase of corrosion potential. Depending on the population density of Fe-rich particle, if the corrosion potential increases to the breakdown potential of surface film, localized corrosion initiates at the sites of breakdown. It is observed that Mg with different Fe contents exhibit the same critical potential value for corrosion initiation. Thus, corrosion potential is a critical factor for the corrosion tolerance limit of Fe in Mg. [ABSTRACT FROM AUTHOR]

The hydrated magnesium-carbon films fabricated in this study are the novel-innovative non-oxide-type transparent electronic material. The films, which have a structure similar to that of magnesium hydroxide, were produced by making Mg x -C y films deposited by magnetron co-sputtering react with water vapor. As the extrinsic defect of hydration magnesium-carbon films, C atoms provided redundant electrons, resulting in a conductivity of approximately 3.31 × 10 −2  Ω·cm. Although the conductivity of hydrated magnesium-carbon films is not prominent comparing to the conventional and widely-used n-type TCO materials, e.g. ITO, the films also showed excellent optical properties, which can be attributed to their low bond energy, with the infrared transmittance of the films being greater than 72% for a plasma wavelength of approximately 10 μm. By varying the atomic C content of the films, a visible-region transmittance greater than 80% could be realized. The optical bandgap of the films was approximately 4.04–6.87 eV and was blue-shifted because of the Moss-Burstein effect. [ABSTRACT FROM AUTHOR]

Magnesium (Mg) is one of the essential nutrients for all living organisms. Plants acquire Mg from the environment and distribute within their bodies in the ionic form via Mg2+- permeable transporters. In Arabidopsis, the plasma membrane-localized magnesium transporter MGT6 mediates Mg2+ uptake under Mg-limited conditions, and therefore is important for the plant adaptation to low-Mg environment. In this study, we further assessed the physiological function of MGT6 using a knockout T-DNA insertional mutant allele. We found that MGT6 was required for normal plant growth during various developmental stages when the environmental Mg2+ was low. Interestingly, in addition to the hypersensitivity to Mg2+ limitation, mgt6 mutants displayed dramatic growth defects when external Mg2+ was in excess. Compared with wild-type plants, mgt6 mutants generally contained less Mg2+ under both low and high external Mg2+ conditions. Reciprocal grafting experiments further underpinned a role of MGT6 in a shoot-based mechanism for detoxifying excessive Mg2+ in the environment. Moreover, we found that mgt6 mgt7 double mutant showed more severe phenotypes compared with single mutants under both low- and high-Mg2+ stress conditions, suggesting that these two MGT-type transporters play an additive role in controlling plant Mg2+ homeostasis under a wide range of external Mg2+ concentrations. [ABSTRACT FROM AUTHOR]

Magnesium alloys are promising candidates for biomedical applications. In this work, influences of composition and heat treatment on the microstructure, the mechanical properties and the corrosion behavior of Mg–Gd–Ca–Zr alloys as potential biomedical implant candidates were investigated. Mg 5 Gd phase was observed at the grain boundaries of Mg–10Gd– x Ca–0.5Zr ( x =0, 0.3, 1.2 wt%) alloys. Increase in the Ca content led to the formation of additional Mg 2 Ca phase. The Ca additions increased both the compressive and the tensile yield strengths, but reduced the ductility and the corrosion resistance in cell culture medium. After solution heat treatment, the Mg 5 Gd particles dissolved in the Mg matrix. The compressive strength decreased, while the corrosion resistance improved in the solution treated alloys. After ageing at 200 °C, metastable β′ phase formed on prismatic planes and a new type of basal precipitates have been observed, which improved the compressive and tensile ultimate strength, but decreased the ductility. [ABSTRACT FROM AUTHOR]

Fe-rich particles that contain silicon were observed in commercially pure magnesium, which contained less than 25 ppm Fe. Based on the simulated phase diagram, silicon, even at low ppm levels, promotes the formation and growth of Fe-rich particles. The studied pure Mg showed a high corrosion rate (>2 mm/year) in 3.5 wt.% NaCl solution, although the Fe content is far below the widely accepted corrosion tolerance limit of Fe (170 ppm by weight). The formation of the Si-containing Fe-rich particles is one of the main reasons for the high corrosion rate observed. Consequently and importantly, the corrosion tolerance limit of iron in magnesium is significantly reduced by the presence of traces of silicon. [ABSTRACT FROM AUTHOR]

Mg-based alloys as revolutionary implantable biomaterials have increasingly attracted considerable attention, owing to their biodegradability in vivo and beneficial effects on biological systems. The degradation process and products of Mg-based alloys have been reported to exhibit significant biological effects on host-tissue responses. However, these effects have not yet been fully understood. This review systemically summarizes and analyses the current understandings and recent research progress in this area. The primary focal points are the biological effects and related mechanisms associated with the degradation behaviour of Mg-based alloys. The biological impacts of the degradation products are elucidated and the arguable or controversial issues are also discussed, providing a pathway toward a greater understanding of the biological implications of Mg-based alloys. Furthermore, based on these biological implications, the restorative potential of Mg-based alloys for applications in tissue repair and regeneration is summarized. Finally, outlooks on biosafety evaluation and design strategies for Mg-based alloy implants are briefly discussed. [ABSTRACT FROM AUTHOR]

Background and Objectives: Hearing loss is a sensory impairment caused by genetic and environmental factors. Previous epidemiological studies of magnesium intake and hearing loss have yielded conflicting results.Methods and Study Design: We investigated the association between serum magnesium concentrations and hearing loss in a population from the Zhejiang region of China. A cross-sectional study of 3,267 participants aged 18 years and older from five hospitals was conducted from October 2016 to May 2018. An audiometric examination was conducted, and hearing thresholds were computed as pure-tone averages (PTAs) at speech (0.5, 1, 2, and 4 kHz) and high frequencies (3, 4, and 6 kHz). Magnesium concentrations were measured using an inductively coupled plasma mass spectrometer.Results: A linear regression analysis revealed a negative association between magnesium levels and hearing losses from lower to high PTAs. After the adjustment of potential confounders, participants in the highest magnesium quartile had a lower PTA (quartile 4: -1.89%; 95% confidence interval (CI: -3.07 to -0.701); p=0.022) and high PTA (quartile 4: -3.05%; 95% CI: -4.64 to -1.46; p=0.005) than those in the lowest quartile. A logistic regression analysis showed a dose-dependent reduction in the odds of high frequency hearing loss across magnesium quartiles. In model 3, after adjusting for all potential confounders, participants with the highest magnesium quartiles had a 54.0% (OR: 0.460; 95% CI: 0.339-0.587) reduction in the odds of high-frequency hearing loss.Conclusions: Higher whole blood levels of magnesium in this population were associated with lower hearing thresholds and risk of hearing loss. [ABSTRACT FROM AUTHOR]

In biomedical applications, degradation behavior of Magnesium (Mg) and its alloys is crucial for its outcomes. Various methods have been adopted to regulate Mg metals degradation, in which oxide layer generation has been considered to be a reliable strategy. However, correlation of magnesium oxide layer surface morphology and magnesium degradation is difficult to clarify due to interruption of oxide layer thickness and co-effect of other surface characteristics. In this work, Mg samples with two distinctive oxide layer morphology were prepared by nanosecond laser processing under N 2 and CO 2 atmospheres, coupled with essential surface and cross-section characterizations using SEM, AFM, TEM, XPS, XRD, and contact angle instrument. Furthermore, oxide layer morphology dependent Mg degradation behavior was investigated by electrochemical experimental, hydrogen precipitation, and pH tests. Results indicated that by changing laser treatment processing gas atmosphere, magnesium oxide morphology generated on sample surface could be tailored while maintaining consistency in thickness and composition. Larger particle size, surface roughness and wettability of magnesium oxide can decrease degradation rate. • Laser induced MgO with different surface characteristics was prepared on Mg. • Mg-c with higher roughness, particle size and wettability show better corrosion resistance than Mg-n. • Particle size of MgO plays a crucial role in the degradation behavior control of Mg. [ABSTRACT FROM AUTHOR]

Inhibition mechanism of sodium dodecyl sulphate (SDS) on Mg alloy was disclosed. Cathodic hydrogen evolution and anodic dissolution were kinetically inhibited. Oxidation reaction of the substrate is facilitated in the presence of SDS. Mg surface is covered by a hydrophobic outer corrosion layer and an inner oxide layer. The inhibition mechanism of sodium dodecyl sulfate (SDS) on Mg alloy in 3.5 wt. % NaCl solution was thoroughly investigated by means of SEM, EPMA, XPS, TEM and electrochemical corrosion tests. The active Mg surface is covered by a hydrophobic outer corrosion layer and a passive inner oxide layer in the presence of SDS, which suppress the cathodic hydrogen evolution and anodic dissolution of the substrate. The electrochemical reaction kinetics is inhibited due to adsorption of SDS in the corrosion products, while the oxidation reaction of the substrate is facilitated by the hydrophobic outer corrosion layer. [ABSTRACT FROM AUTHOR]