Effect of Mg<Superscript>2+</Superscript> concentration on biocompatibility of pure magnesium

The aim of the present study is to find the correlation between the Mg²⁺ concentration degraded from pure magnesium material and the biocompatibility of the material. Hemolysis ratio (HR) of the extracts of pure magnesium with different Mg²⁺ concentration were measured according to ISO 10993.4 standard. The cytotoxicity tests were carried out by both indirect contact with fibroblast L929 and preosteoblasts MC3T3-E1, and MTT tests were used. Cytotoxicity of the pure magnesium with and without surface modification was further evaluated by direct contact method. Samples were cultured with Osteoblast MC3T3-E1 and the effects of the material on viability and activity of cells were discussed. The results showed that the hemolysis rate and cytotoxicity of the modified Mg could meet the requirement for biomaterials. In our test, the hemolysis rate of the extracts was qualified when the concentration of Mg²⁺ ? 42 mg/L; the extracts with 202 mg/L Mg²⁺ met the cytotoxicity requirement, and the extracts with 156 mg/L Mg²⁺ promoted cell proliferation. Therefore, the biocompatibility of magnesium-based materials can be improved by suitable surface modification.     

Corrosion and bone response of magnesium implants after surface modification by heat-self-assembled monolayer

The aim of the present study is to find the correlation between the Mg²⁺ concentration degraded from pure magnesium material and the biocompatibility of the material. Hemolysis ratio (HR) of the extracts of pure magnesium with different Mg²⁺ concentration were measured according to ISO 10993.4 standard. The cytotoxicity tests were carried out by both indirect contact with fibroblast L929 and preosteoblasts MC3T3-E1, and MTT tests were used. Cytotoxicity of the pure magnesium with and without surface modification was further evaluated by direct contact method. Samples were cultured with Osteoblast MC3T3-E1 and the effects of the material on viability and activity of cells were discussed. The results showed that the hemolysis rate and cytotoxicity of the modified Mg could meet the requirement for biomaterials. In our test, the hemolysis rate of the extracts was qualified when the concentration of Mg²⁺ ⩽ 42 mg/L; the extracts with 202 mg/L Mg²⁺ met the cytotoxicity requirement, and the extracts with 156 mg/L Mg²⁺ promoted cell proliferation. Therefore, the biocompatibility of magnesium-based materials can be improved by suitable surface modification.     

In vitro degradation,hemolysis and MC3T3-E1 cell adhesion of biodegradable Mg–Zn alloy

In this study a kind of patent binary Mg–6 wt.%Zn magnesium alloy was investigated as degradable biomedical material. The results of in vitro degradation including electrochemical measurements and immersion tests in simulated body fluid (SBF) revealed that zinc could elevate both the corrosion potential and Faraday charge transfer resistance of magnesium and thus improve the corrosion resistance. XRD and EDS analysis proved that the corrosion products on the surface of Mg–Zn contained hydroxyapatite (HA), Mg(OH)₂ and other Mg/Ca phosphates, which could reduce the degradation rate. The degradation process of magnesium alloy and the mechanism of corrosion layer formation were also discussed in this work, i.e. the byproducts of degradation of magnesium, Mg²⁺ and OH^?, reacted with the phosphate and Ca²⁺ in the SBF, thus the corrosion layer containing HA, Mg(OH)₂ and other magnesium-substituted apatite precipitated in corrosion pits and covered the surface of magnesium alloy.The hemolysis test found that the hemolysis rate of Mg–Zn was 3.4%, which is lower than the safe value of 5% according to ISO 10993-4. For the cell culture experiments, after 2 h incubation the pre-osteoblastic cell MC3T3-E1 was able to adhere and spread on the corrosion layer of Mg–Zn alloy, indicating that despite the fluctuation of pH value of DMEM culture solution, Mg–Zn alloy could still support the earlier adhesion of pre-osteoblastic cells on the surface. Hemolysis and adhesion of cells display good biocompatibility of Mg–Zn alloy in vitro.     

Nanostructured Titanate with Different Metal Ions on the Surface of Metallic Titanium: A Facile Approach for Regulation of rBMSCs Fate on Titanium Implants

Titanium (Ti) is widely used for load‐bearing bio‐implants, however, it is bio‐inert and exhibits poor osteo‐inductive properties. Calcium and magnesium ions are considered to be involved in bone metabolism and play a physiological role in the angiogenesis, growth, and mineralization of bone tissue. In this study, a facile synthesis approach to the in situ construction of a nanostructure enriched with Ca²⁺ and Mg²⁺ on the surface of titanium foil is proposed by inserting Ca²⁺ and Mg²⁺ into the interlayers of sodium titanate nanostructures through an ion‐substitution process. The characteriz 0.67, and 0.73 nm ation results validate that cations can be inserted into the interlayer regions of the layered nanostructure without any obvious change of morphology. The cation content is positively correlated to the concentration of the solutions employed. The biological assessments indicate that the type and the amount of cations in the titanate nanostructure can alter the bioactivity of titanium implants. Compared with a Na⁺ filled titanate nanostructure, the incorporation of divalent ions (Mg²⁺, Ca²⁺) can effectively enhance protein adsorption, and thus also enhance the adhesion and differentiation ability of rat bone‐marrow stem cells (rBMSCs). The Mg²⁺/Ca²⁺‐titanate nanostructure is a promising implantable material that will be widely applicable in artificial bones, joints, and dental implants.     

Magnetic Field Boosts the Transmembrane Transport Efficiency of Magnesium Ions from PLLA Bone Scaffold

In the system of magnesium-loaded scaffolds, the effect of magnesium ions (Mg²⁺) on the osteogenesis induction is restricted due to the low transmembrane transport efficiency of Mg²⁺ into the cell, which limits the application for bone defect repair. Inspired by the fact that magnetic field can regulate ion channel proteins on the cell membrane, magnetite nanoparticle is introduced into the poly (l-lactic acid) /magnesium oxide composite in this study, and a magnetic magnesium-loaded bone scaffold is prepared via selective laser sintering . Notably, the activities of the Mg²⁺ channel protein (MAGT1) on the membrane of bone marrow mesenchymal stem cells (rBMSCs) are enhanced via magnetic torque effect (via integrin αV β3/actin), under the action of static magnetic field (SMF), which promoted rBMSCs to capture Mg²⁺ in the microenvironment and induced osteogenesis. In vitro experiments showed that the magnetic magnesium-loaded scaffold, under the action of SMF, can accelerate the inflow of Mg²⁺ from surrounding microenvironment, which improved cellular activities, osteogenesis-related gene expression (ALP, Runx2, OCN, and OPN), and mineralization. Besides, in vivo skull defect repair experiments showed that the scaffolds possessed good ability to promote bone differentiation and new bone regeneration.     

Mg- and Zn-modified calcium phosphates prepared by biomimetic precipitation and subsequent treatment at high temperature

Powders of magnesium-modified as well as zinc-modified calcium phosphates (Me-β-TCP and HA) with a (Ca²⁺+Mg²⁺+Zn²⁺+Na⁺+K⁺)/P ratio of 1.3–1.4 and various Me²⁺/(Me²⁺+Ca²⁺) ratios (from 0.005 to 0.16) were prepared in biomimetic electrolyte systems at pH 8, mother liquid maturation and further syntering at 600–1000°C. Some differences in zinc and magnesium modifications have been prognosed on the basis of thermodynamic modeling of the studied systems and explained by the Mg²⁺ and Zn²⁺ ion chemical behaviour. The temperature as well as the degree of Zn²⁺ and Mg²⁺ ions substitutions were found to stabilize the β-TCP structure and this effect was more prononced for zinc. Thus, zinc-modified β-TCP powders consisting of idiomorphic crystals were obtained through sintering of Zn²⁺ ion substituted calcium phosphates precursors at 800–1000°C. The Mg²⁺ ion substitution leads to obtaining magnesium-modified β-TCP with spherical grains.     

Amplified fluorescence of Mg2+ selective red-light emitting carbon dot in water and direct evaluation of creatine kinase activity

Carbon quantum dot/carbon dot (CD) exhibiting sustained photoluminescence at longer wavelengths in aqueous solution is difficult to prepare, but has enormous potential in biomedical applications. For the first time, we report the magnesium(II) selective fluorescence enhancement of a red-light emitting anthrarufin and boric acid-derived CD in aqueous solution for direct evaluation of creatine kinase (CK) enzyme activity. The CD displayed visually detectable, intense red fluorescence only in the presence of magnesium ion (Mg²⁺) at physiological pH value when irradiated with an ultraviolet (UV) source. Concurrently, a significant increase in steady-state fluorescence intensity and fluorescence lifetime was documented. A time-dependent density functional theory (TD-DFT) analysis displayed a bathochromic shift in UV-visible (vis) absorption, and increased oscillator strength of transition resulting from the selective chelation of Mg²⁺ with β-hydroxy keto functionality on the surface of the CD. The CD-Mg²⁺ assembly was subsequently used to conceptualize the detection of CK directly through the exploration of the differential binding affinity of Mg²⁺ with adenosine triphosphate (ATP), adenosine diphophate (ADP), and CD that is otherwise not possible with commercially available kits as of today. Thus, the report delineated here usher grandeur potential of CD for biological explorations related to Mg²⁺ or ATP sensing and monitoring of Mg²⁺-dependent enzymatic activity through a clear understanding of the chemistry.

     

Formation mechanism of calcium phosphate coating on micro-arc oxidized magnesium

A calcium phosphate coating was prepared on the surface of micro-arc oxidized magnesium by a chemical method. The microstructure evolution of the coating was characterized by X-ray diffraction, Fourier-transformed infrared spectroscopy and scanning electron microscopy. The results showed that Ca₁₀(PO₄)₆(OH)₂ (HA) was firstly formed on the surface of micro-arc oxidized magnesium, followed by flake-like CaHPO₄·2H₂O (DCPD). The solution pH and Ca²⁺ concentration had intense influence on the formation of calcium phosphate coating. Acidic Ca²⁺ enrichment solution was favourable for HA formation on the surface of micro-arc oxidized magnesium. High concentration of HPO₄²⁻ and low concentration of Ca²⁺ in acidic solution improved the formation of DCPD coating.     

Microwave-assisted method for preparation of Zn1−xMgxO nanostructures and their activities for photodegradation of methylene blue

Nanostructures of Zn_1−xMg_xO (0 ⩽ x ⩽ 0.2) were prepared in water by one-pot method under microwave irradiation for 5 min. In this method, zinc acetate, magnesium nitrate and sodium hydroxide were used as starting materials without using any additive and post preparation treatment. The nanostructures were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), electrochemical impedance spectroscopy (EIS), Fourier transform-infrared (FT-IR), and the Brunauer–Emmett–Teller (BET) techniques. The nanostructures have wurtzite hexagonal crystalline phase and doping of Mg²⁺ ions does not change the phase of ZnO. The SEM and TEM images show that morphology of the samples is changing by doping of Mg²⁺ ions. The EIS data show that by doping the ion, interfacial charge transfer resistance of the nanostructures decreases. Photocatalytic activity of the nanostructures was evaluated by degradation of methylene blue (MB) under UV irradiation. The degradation rate constant on the nanostructures with 0.15 mol fraction of Mg²⁺ ions is about 2-fold greater than for ZnO. Moreover, influence of various operational parameters such as microwave irradiation time, calcination temperature, weight of catalyst, concentration of MB, pH of solution and scavengers of reactive species on the degradation rate constant was investigated and the results were discussed.     

Investigation on the <Emphasis Type="Italic">in vitro</Emphasis> cytocompatibility of Mg-Zn-Y-Nd-Zr alloys as degradable orthopaedic implant materials

Mg-Zn-Y-Nd-Zr alloy has been developed as a new type of biodegradable orthopaedic implant material by the authors’ research group with its excellent mechanical properties and controllable degradation rate. In this study, the cytocompatibility of Mg-Zn-Y-Nd-Zr alloy was systematically evaluated through in vitro cell culture method. MTT assay was applied to evaluate the cytotoxicity of Mg-Zn-Y-Nd-Zr alloy and no toxic effect was observed on L929 and MC3T3-E1 cells followed the protocol of ISO 10993 standard. Considering the potential ion accumulation in the bony environment, this study further investigated the cytotoxic effect of accumulated metallic ions during the alloy degradation by extending the extract preparation time. When the extract preparation time was prolonged to 1440?h, the accumulated metallic ions leaded to severe cell apoptosis, of which the combined ion concentration was determined as 39.5–65.8?µM of Mg²⁺, 3.5–5.9?µM of Zn²⁺, 0.44–0.74?µM of Y³⁺, 0.3–0.52?µM of Nd³⁺ and 0.11–0.18?µM of Zr⁴⁺ for L929, and 65.8–92.2?µM of Mg²⁺, 5.9–8.3?µM of Zn²⁺, 0.74–1.04?µM of Y³⁺, 0.52–0.73?µM of Nd³⁺ and 0.18–0.25?µM of Zr⁴⁺ for MC3T3-E1 cells. Besides the cell viability assessment, high expression of ALP activity and calcified nodules implied that metal elements in Mg-Zn-Y-Nd-Zr alloys can promote the osteogenic differentiation. Hence, excellent cytocompatibility has equipped Mg-Zn-Y-Nd-Zr alloy as a promising candidate for orthopaedic implant application, which can remarkably guide the magnesium-based alloy design and provide scientific evidence for clinical practice in future.     

Influence of Tris in simulated body fluid on degradation behavior of pure magnesium

In current paper, influence of tris-hydroxymethyl-aminomethane (tris) in simulated body fluid (SBF) on degradation behavior of pure magnesium is investigated using electrochemical tests as well as degradation measurement. Our results shows that tris mainly affects earlier degradation behavior of pure magnesium alloy. Tris and HCl used in preparation of SBF will form Tris–HCl which only lowers corrosion potential of magnesium slightly but accelerates degradation rates of pure magnesium by teens times. Consumption of OH^? generated during magnesium dissolution by Tris–HCl progressively promotes transformation from Mg to Mg²⁺, which is the main reason for quite high degradation rate of pure magnesium in SBF. Pure magnesium is also more sensitive to pitting corrosion due to inclusion of Tris–HCl in SBF. This study deepens the understanding on degradation mechanism of biomedical magnesium alloys.     

Cyclophospholipids Increase Protocellular Stability to Metal Ions

Model protocells have long been constructed with fatty acids, because these lipids are prebiotically plausible and can, at least theoretically, support a protocell life cycle. However, fatty acid protocells are stable only within a narrow range of pH and metal ion concentration. This instability is particularly problematic as the early Earth would have had a range of conditions, and extant life is completely reliant on metal ions for catalysis and the folding and activity of biological polymers. Here, prebiotically plausible monoacyl cyclophospholipids are shown to form robust vesicles that survive a broad range of pH and high concentrations of Mg²⁺, Ca²⁺, and Na⁺. Importantly, stability to Mg²⁺ and Ca²⁺ is improved by the presence of environmental concentrations of Na⁺. These results suggest that cyclophospholipids, or lipids with similar characteristics, may have played a central role during the emergence of Darwinian evolution.     

Surface enrichment of biomimetic apatites with biologically-active ions Mg2+ and Sr2+: A preamble to the activation of bone repair materials

The surface activation of calcium phosphate-based biomaterials for bone repair is an emerging route for improving bone regeneration processes. One way for such activation is through the exchange of surface calcium ions with biologically-active cations such as Mg²⁺ or Sr²⁺. In this work, the interactions of non-carbonated and carbonated nanocrystalline apatites with Mg²⁺ and Sr²⁺ were investigated by means of ion exchange experiments in solution. Langmuir-type isotherms were determined. For both Sr and Mg, a greater uptake was observed on the carbonated sample, and on both types of apatites the maximum strontium uptake was greater than that of magnesium. Inverse exchanges showed that the proportion of reversibly fixed ions after surface exchange was close to 85% for Mg and 75–80% for Sr. The results are related to the presence of a surface hydrated layer on the nanocrystals and possible exchange mechanisms are discussed. Our results favor the hypothesis of hetero-ionic surface exchanges (Mg²⁺↔Ca²⁺, Sr²⁺↔Ca²⁺) within the hydrated layer, and some analogy with octacalcium phosphate (OCP) is considered. This work should prove helpful for the control and understanding of the activation of synthetic apatite-based powders or scaffolds with bioactive elements, as well as for the global understanding of biomineralization processes.     

球形氢氧化镁的制备及其晶体生长动力学

制备花状球形氢氧化镁粉体,研究了几种关键因素对镁回收率的影响和氢氧化镁的晶体生长动力学.结果表明,随着反应溶液中Mg~(2 )初始浓度和pH值的提高,镁的回收率提高;提高反应温度使镁的回收率提高,但当温度超过60℃后,反应溶液中氨的大量挥发使其pH值迅速降低,因而镁回收率下降;陈化可以提高镁的回收率,当陈化时间超过60 min后因镁已完全沉淀,回收率不再提高.在最佳工艺条件下用氨法制备的氢氧化镁颗粒为花状球形,形状规则,分散性好,粒度均匀,粒径约2μm,单片厚度约30 nm.晶体生长动力学研究表明,析出Mg(OH)_2晶体的质量和Mg(OH)_2晶粒平均粒径随着时间呈指数增长.     

Influence of Additions of Water on the Quality of Filled Anodic Oxide Coatings

We investigate the influence of anion-cation composition of an aqueous medium on the etching rate in an acid electrolyte and the resistance of the insulation of a filled oxide coating. We reveal the cations and anions of the aqueous medium that increase the etching rate of the coating and decrease its insulation resistance. We establish that Al³⁺ and Mg²⁺ cations and SiO ₃ ^2- anions have a considerable effect on the quality of the filled coating. A high-quality coating is obtained if their concentrations in the aqueous medium are at most (mg/liter) 100 for Al³⁺, 700 for Mg²⁺, 800 for Cl^–, and 13 for SiO ₃ ^2- . The optimum pH of the environment is equal to 6 and the time of treatment of a coating in distilled water is equal to 60 ± 5 min.     

Highly Branched VS4 Nanodendrites with 1D Atomic‐Chain Structure as a Promising Cathode Material for Long‐Cycling Magnesium Batteries

Rechargeable magnesium batteries have attracted increasing attention due to the high theoretical volumetric capacities, dendrite formation‐free characteristic and low cost of Mg metal anodes. However, the development of magnesium batteries is seriously hindered by the lack of capable cathode materials with long cycling life and fast solid‐state diffusion kinetics for highly‐polarized divalent Mg²⁺ ions. Herein, vanadium tetrasulfide (VS₄) with special one‐dimensional atomic‐chain structure is reported to be able to serve as a favorable cathode material for high‐performance magnesium batteries. Through a surfactant‐assisted solution‐phase process, sea‐urchin‐like VS₄ nanodendrites are controllably prepared. Benefiting from the chain‐like crystalline structure of VS₄, the S₂^2‐ dimers in the VS₄ nanodendrites provide abundant sites for Mg²⁺ insertion. Moreover, the VS₄ atomic‐chains bonded by weak van der Waals forces are beneficial to the diffusion kinetics of Mg²⁺ ions inside the open channels of VS₄. Through a series of systematic ex situ characterizations and density functional theory calculations, the magnesiation/demagnesiation mechanism of VS₄ are elucidated. The VS₄ nanodendrites present remarkable performance for Mg²⁺ storage among existing cathode materials, exhibiting a remarkable initial discharge capacity of 251 mAh g^‐1 at 100 mA g^‐1 and an impressive long‐term cyclability at large current density of 500 mA g^‐1 (74 mAh g^‐1 after 800 cycles).     

Microwave assisted synthesis of amorphous magnesium phosphate nanospheres

Magnesium phosphate (MgP) materials have been investigated in recent years for tissue engineering applications, attributed to their biocompatibility and biodegradability. This paper describes a novel microwave assisted approach to produce amorphous magnesium phosphate (AMP) in a nanospherical form from an aqueous solution containing Mg²⁺ and HPO₄ ^2?/PO₄ ^3?. Some synthesis parameters such as pH, Mg/P ratio, solution composition were studied and the mechanism of AMP precursors was also demonstrated. The as-produced AMP nanospheres were characterized and tested in vitro. The results proved these AMP nanospheres can self-assemble into mature MgP materials and support cell proliferation. It is expected such AMP has potential in biomedical applications.     

Ion-selective properties of metastable (VO)<Subscript>0.09</Subscript>V<Subscript>0.18</Subscript>Mo<Subscript>0.82</Subscript>O<Subscript>3</Subscript> · 0.54H<Subscript>2</Subscript>O

This paper describes a thin-film solid electrode with an ion-sensitive membrane based on the mixed oxide (VO)_0.09V_0.18Mo_0.82O₃ · 0.54H₂O. The electrode is selective for tetravalent vanadium in the concentration range 3 ≤ pC _V ⁴⁺ ≤ 5 and acidity range 4.5 ≤ pH ≤ 6, with a slope close to the theoretical value. In the range 1 ≤ pH < 5, the electrode responds to changes in hydrogen ion concentration, with a slope of 50 ± 2 mV/pH. Its alkali-metal-ion response shows up in the range 1 ≤ pC _M ⁺ ≤ 4 for pH ≥ 6. We examine the effect of the Li⁺, K⁺, Na⁺, Cs⁺, Rb⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Co²⁺, Ni²⁺, Mn²⁺, Al³⁺, Cr³⁺, and VO₂⁺ ions on the potential of the electrode and determine its selectivity coefficients for these cations.     

Interlayer‐Spacing‐Regulated VOPO4 Nanosheets with Fast Kinetics for High‐Capacity and Durable Rechargeable Magnesium Batteries

Owing to the low‐cost, safety, dendrite‐free formation, and two‐electron redox properties of magnesium (Mg), rechargeable Mg batteries are considered as promising next‐generation secondary batteries with high specific capacity and energy density. However, the clumsy Mg²⁺ with high polarity inclines to sluggish Mg insertion/deinsertion, leading to inadequate reversible capacity and rate performance. Herein, 2D VOPO₄ nanosheets with expanded interlayer spacing (1.42 nm) are prepared and applied in rechargeable magnesium batteries for the first time. The interlayer expansion provides enough diffusion space for fast kinetics of MgCl⁺ ion flux with low polarization. Benefiting from the structural configuration, the Mg battery exhibits a remarkable reversible capacity of 310 mAh g^?1 at 50 mA g^?1, excellent rate capability, and good cycling stability (192 mAh g^?1 at 100 mA g^?1 even after 500 cycles). In addition, density functional theory (DFT) computations are conducted to understand the electrode behavior with decreased MgCl⁺ migration energy barrier compared with Mg²⁺. This approach, based on the regulation of interlayer distance to control cation insertion, represents a promising guideline for electrode material design on the development of advanced secondary multivalent‐ion batteries.     

Morphology and luminescent properties of Al<Superscript>3+</Superscript>/Mg<Superscript>2+</Superscript>-doped Y<Subscript>2</Subscript>O<Subscript>3</Subscript>:Eu<Superscript>3+</Superscript> phosphor

Al³⁺/Mg²⁺ doped Y₂O₃:Eu phosphor was synthesized by the glycine-nitrate solution combustion method. In contrast to Y₂O₃:Eu which showed an irregular shape of agglomerated particles (the mean particle size >10 μm), the morphology of Al³⁺/Mg²⁺ doped Y₂O₃:Eu crystals was quite regular. Al³⁺/Mg²⁺ substituting Y³⁺ in Y₂O₃:Eu resulted in an obvious decrease of the particle size. Meanwhile, higher the Al³⁺/Mg²⁺ concentration, smaller the particle size. In particular, the introduction of Al³⁺ ion into Y₂O₃ lattice induced a remarkable increase of PL and CL intensity. While, for Mg²⁺ doped Y₂O₃:Eu samples, their PL and CL intensities decreased. The reason that causes the variation of PL and CL properties for Al³⁺ and Mg²⁺ doped Y₂O₃:Eu crystals was concluded to be related to sites of Al³⁺ and Mg²⁺ ions inclined to take and the difference of ion charge.