Magnesium Alloys For Biomedical Applications Research Articles

Biocompatibility and mechanical performance of magnesium alloys for biomedical application- a state of the art review

This review addresses the problems associated with various types of implants, providing a brief background on their challenges and surgical implications. Preclinical and clinical studies are discussed to understand the causes of implant failures. The review specifically examines the potential of magnesium-based alloys in biomedical applications, focus on existing research to offer a comprehensive overview of their advantages and disadvantages in biodegradable implants. It explores how alloying elements can enhance mechanical properties and corrosion behavior in Mg alloys. This review indicates how specific percentages of different alloying elements, combined with suitable manufacturing and post-processing techniques, can yield optimized results. Additionally, the review assesses the impact of magnesium alloy degradation on the healing process and suggests strategies to mitigate adverse effects. By thoroughly analyzing the literature, this paper offers valuable insights into fabricating magnesium-based implants to achieve ideal mechanical and corrosion properties, enhancing their effectiveness in biomedical applications.

Engineering Corrosion Resistance in Magnesium Alloys for Biomedical Applications: A Synergy of Zn/Ca Atomic Ratio and Texture-Based Approach

Magnesium (Mg) and Magnesium-Zinc-Calcium alloys present a compelling option for biodegradable implant materials. Utilizing Vacuum Induction Casting, Mg–2.5Zn-xCa (with x = 0.3, 0.5, 0.9, 1.15 wt%) alloys were fabricated and subjected to hot-rolling for thermo-mechanical processing. The hot-rolled Mg–2.5Zn-0.3Ca alloy exhibits the lowest corrosion rate along with the highest basal texture. Increasing the Zn/Ca atomic ratio intensifies the basal texture and enhances corrosion resistance. Elevated Zn concentration improves corrosion resistance via Ca2Mg6Zn3 phase formation, while increased Ca content diminishes corrosion resistance due to the Mg2Ca phase. Advancement of this alloy is poised to extend Mg alloy use in innovative biomedical bone implants.

Machine learning-guided accelerated discovery of structure-property correlations in lean magnesium alloys for biomedical applications

Magnesium alloys are emerging as promising alternatives to traditional orthopedic implant materials thanks to their biodegradability, biocompatibility, and impressive mechanical characteristics. However, their rapid in-vivo degradation presents challenges, notably in upholding mechanical integrity over time. This study investigates the impact of high-temperature thermal processing on the mechanical and degradation attributes of a lean Mg-Zn-Ca-Mn alloy, ZX10. Utilizing rapid, cost-efficient characterization methods like X-ray diffraction and optical microscopy, we swiftly examine microstructural changes post-thermal treatment. Employing Pearson correlation coefficient analysis, we unveil the relationship between microstructural properties and critical targets (properties): hardness and corrosion resistance. Additionally, leveraging the least absolute shrinkage and selection operator (LASSO), we pinpoint the dominant microstructural factors among closely correlated variables. Our findings underscore the significant role of grain size refinement in strengthening and the predominance of the ternary Ca2Mg6Zn3 phase in corrosion behavior. This suggests that achieving an optimal blend of strength and corrosion resistance is attainable through fine grains and reduced concentration of ternary phases. This thorough investigation furnishes valuable insights into the intricate interplay of processing, structure, and properties in magnesium alloys, thereby advancing the development of superior biodegradable implant materials.

Multifunctional poly(allylamine hydrochloride)/bioactive glass layer by layer surface coating on magnesium alloy for biomedical applications

The present study reports on a novel multilayer coating for biodegradable magnesium (Mg) alloy substrates. This coating contains soy protein hydrolysate (SPH), poly(allylamine hydrochloride) (PAH), and folic acid (FA) templated bioactive glass (BG) nano particles. The multilayer, designated as SPH/(PAH/BG)n, was coated onto an alkaline-treated Mg alloy surface (AMgS) through a dip-coating process with various numbers of cycles (n = 5and 7) using a layer-by-layer (LbL) assembly. The BG particles had an average diameter of 12.53 ± 2.22 nm and were embedded with therapeutic FA molecules. Scratch testing, wettability, and roughness tests showed excellent adherence of the SPH/(PAH/BG)7 coating on AMgS, making it suitable for cell attachment. Electrochemical measurements in Hanks balanced salt solution (HBSS) demonstrated that the SPH/(PAH/BG)7 coating improved the corrosion resistance of the Mg alloy. SPH/(PAH/BG)7 coated substrate showed a maximum protective efficacy of 98.4041 %, thanks to the bioactive nature of BG. High-resolution XPS and XRD analyses on SPH/(PAH/BG)7/AMgS confirmed the corrosion deposition of Mg(OH)2, MgHPO4.H2O, CaHPO4.H2O, SiO2, MgCO3 and CaCO3 on the substrate surface after immersion in HBSS for 10 d at 37 °C. The LbL coated Mg substrate also showed excellent cytocompatibility by hemolysis assay These results suggest that the SPH/(PAH/BG)7/AMgS material has multifunctional properties and can be a possible alternative for biomedical applications of Mg alloys.

Tuning the long-term corrosion behaviour of biodegradable WE43 magnesium alloy by PEO coating

Plasma electrolytic oxidation (PEO) coatings can control fast degradation of next-generation biodegradable magnesium alloys for biomedical applications. In this work, we studied the effect of a PEO coating on the long-term corrosion behaviour of medical-grade WE43 magnesium alloy. In vitro experiments were performed for periods of up to 4 weeks in an organic fluid Dulbecco's Modified Eagles' Medium (DMEM). The average corrosion rates were measured using the hydrogen evolution method, and the degradation of the mechanical integrity were quantified by tensile test. Susceptibility towards localized corrosion was evaluated by scanning electron microscopy (SEM) images of cross-sections. Moreover, energy-dispersive X-ray spectroscopy (EDS) mappings and X-ray diffraction (XRD) were utilised for analysing the corrosion layer. Experimental results reveal significant changes in the product layer formation due to the PEO coating in phosphate-based electrolyte. The porous morphology of the coating with an initial thickness of ∼20 ± 5 μm changed significantly during the corrosion process, and a growing Mg-O-rich layer of 32 μm after 28 days was detected at the substrate interface. In contrast to the non-coated control group, no carbon-enriched area was observed. These findings imply significant long-term corrosion protection of the PEO coating. The results provide valuable information for a better understanding of the in vitro degradation process in PEO-coated magnesium alloys.

Plasma Electrolytic Oxidation Treatment of AZ31 Magnesium Alloy for Biomedical Applications: The Influence of Applied Current on Corrosion Resistance and Surface Characteristics

Magnesium alloys are an exciting challenge for the biomaterials field given their well-established biodegradability and biocompatibility. However, when exposed to biological fluids, their rapid degradation and hydrogen release are the main drawbacks for clinical applications. This work aimed to investigate the influence of the current density applied during the plasma electrolytic oxidation (PEO) treatment on the durability of an AZ31 magnesium alloy. In particular, specific interest was directed to the degradation rate undergone by the PEO coating, obtained under two different current density conditions, when exposed to Hank’s solution at 37 °C to simulate the physiological environment, employing the techniques of potentiodynamic polarization and electrochemical impedance spectroscopy. Experimental results highlighted that the plasma electrolytic oxidation technique resulted in an improvement in the corrosion resistance of the magnesium alloy in the test solution. The current density affected the morphology of the coating. In particular, the anodic oxide coating obtained by applying the highest current density showed a higher thickness and fewer but larger pores, while the lowest current density generated a thinner PEO coating characterized by several but smaller pores. Surprisingly, the best corrosion resistance has been exhibited by the anodic oxide coating grown at the highest current density.

Ceria-based coatings on magnesium alloys for biomedical applications: a literature review.

Magnesium alloys are being studied for use in temporary orthopedic implants because of their mechanical properties, which are similar to those of human bone, and their good biocompatibility. However, their application is limited due to their rapid degradation, and early loss of their mechanical properties, decreasing the stability of the implant and its proper synchronization with tissue regeneration. In this regard, various surface coatings have been used to improve their biological, physico-chemical and biodegradation properties. Currently, one of the most explored strategies is using smart coatings because of their self-healing properties that can slow down the corrosion process of Mg and its alloys. Ceria-based materials show promise as coatings for these alloys. Their unique redox capacity not only provides Mg alloys with good self-healing properties but also interesting biological properties, which are described in this paper. Despite this, some problems and challenges related to the biocompatibility and application of these materials in coatings remain unsolved. In this article, a critical review is presented summarizing the most representative literature on ceria-based coatings on Mg alloys for their potential use as biomaterials. The results show that ceria is a versatile material that may be used in industrial and biomedical applications.

Natural Coatings and Surface Modifications on Magnesium Alloys for Biomedical Applications

Magnesium (Mg) alloys have great potential in biomedical applications due to their incomparable properties regarding other metals, such as stainless steels, Co-Cr alloys, and titanium (Ti) alloys. However, when Mg engages with body fluids, its degradation rate increases, inhibiting the complete healing of bone tissue. For this reason, it has been necessary to implement protective coatings to control the rate of degradation. This review focuses on natural biopolymer coatings used on Mg alloys for resorbable biomedical applications, as well as some modification techniques implemented before applying natural polymer coatings to improve their performance. Issues such as improving the corrosion resistance, cell adhesion, proliferation, and biodegradability of natural biopolymers are discussed through their basic comparison with inorganic-type coatings. Emphasis is placed on the expected biological behavior of each natural polymer described, to provide basic information as a reference on this topic.

A review on magnesium alloys for biomedical applications.

Magnesium (Mg) and Mg alloys are considered as potential candidates for biomedical applications because of their high specific strength, low density, and elastic modulus, degradability, good biocompatibility and biomechanical compatibility. However, the rapid corrosion rate of Mg alloys results in premature loss of mechanical integrity, limiting their clinical application in load-bearing parts. Besides, the low strength of Mg alloys restricts their further application. Thus, it is essential to understand the characteristics and influencing factors of mechanical and corrosion behavior, as well as the methods to improve the mechanical performances and corrosion resistance of Mg alloys. This paper reviews the recent progress in elucidating the corrosion mechanism, optimizing the composition, and microstructure, enhancing the mechanical performances, and controlling the degradation rate of Mg alloys. In particular, the research progress of surface modification technology of Mg alloys is emphasized. Finally, the development direction of biomedical Mg alloys in the future is prospected.

Microstructure, corrosion resistance, and antibacterial properties of an Ag/Mg-Al layered double hydroxide coating synthesized in situ on biomedical Mg-Zn-Ca alloy

A one-step hydrothermal treatment was used to deposit a nano silver-loaded magnesium-aluminum hydrotalcite (Ag/Mg-Al) layered double hydroxide (LDH) coating onto the surface of a Mg-Zn-Ca alloy to improve the corrosion resistance and antibacterial properties of magnesium alloys for biomedical applications. The effect of experimental parameters such as temperature and time on the microstructure, compositions, and corrosion resistance of the Ag/LDH coating during the hydrothermal treatment was investigated to optimize the preparation process. Additionally, the in vitro degradation performance, antibacterial performance and biocompatibility of the coating were evaluated to determine the optimal preparation condition. The results show that when the LDH–NO 3 – coating is prepared at 110 °C for 10 h, the constituting silver particles (dimensions, 10–30 nm) are obtained, while the corrosion current density and the corrosion rate decrease to 4.41 μA/cm 2 and 0.27 mm/year, respectively. The antibacterial experiment demonstrates that the coating effectively inhibits the reproduction of Escherichia coli while offering remarkable biocompatibility.

Analysis of the corrosion performance of binder jet additive manufactured magnesium alloys for biomedical applications

Binder jet printing (BJP) is a state-of-the-art additive manufacturing technique for producing porous magnesium structures. Porous Mg-Zn-Zr based BJP samples were assessed for corrosion performance in simulated body fluids by electrochemical and hydrogen evolution measurements. The corrosion rates of the BJP specimens were significantly higher than solid controls, even after accounting for their larger surface areas, suggesting that the BJP microstructure is detrimental to corrosion performance. X-ray computed tomography revealed nonuniform corrosion within the porous structure, with corrosion products forming on the pore walls. Impregnating the pores with hydroxyapatite or polymers greatly improved the corrosion resistance of the BJP samples.

Design of multilayer hybrid sol-gel coatings with bifunctional barrier-bioactive response on the Elektron 21 magnesium alloy for biomedical applications

The present study aims to develop multilayer barrier-bioactive hybrid sol-gel coatings from a mixture of the silane precursors tetraethylorthosilicate (TEOS) and glycidoxypropyltriethoxysilane (GPTMS) deposited on the Elektron 21 magnesium alloy. The purpose of the inner layer (barrier coating) was to provide corrosion protection to the magnesium alloy, whereas the outer layer (bioactive coating) was doped with different Ca and Mg contents to produce a bioactive material. The coatings were characterised using scanning electron microscopy (SEM) and their corrosion behaviour was evaluated by anodic polarisation and electrochemical impedance spectroscopy after immersion in simulated body fluid (SBF) at 37 ± 0.5 °C. The experimental results showed that the multilayer coatings increased the corrosion resistance of the alloy up to three orders of magnitude during immersion in SBF solution. On the other hand, the presence of Ca and Mg in the bioactive coating promoted the growth of apatite-like phases. However, an increment of salt content favoured the formation of porous coatings, which allowed the access of the electrolyte to the substrate leading to their rapid deterioration. Despite the latter, this research endorses the premise that the TEOS-GPTMS hybrid system represents a promising alternative to produce bifunctional barrier-bioactive coatings.

Magnesium alloys for biomedical application: Advanced corrosion control through surface coating

Several magnesium alloys are increasingly used for a variety of biomedical applications, owing to their favorable mechanical and biomedical properties. However, in vivo corrosion in aqueous environment including Cl ion-rich extracellular fluid (ECF) requires the application of protective coatings as well as the development of advanced alloy formulations with increased corrosion resistance and uniform, non-localized dissolution modes. This contribution reviews recent promising approaches towards improved biostability of Mg alloys during in vitro contact with simulated body fluid (SBF) as well as in vivo exposure to ECF. Emphasis is being put on surface coatings for corrosion protection as well as on functional osseoconductive coatings that stimulate tissue ingrowth.

Magnesium Alloys for Biomedical Applications

Interest in magnesium alloys as biodegradable metals has strongly grown over the last decades [...]

Rare-earth- and aluminum-free, high strength dilute magnesium alloy for Biomedical Applications

Lightweight, recyclable, and plentiful Mg alloys are receiving increased attention due to an exceptional combination of strength and ductility not possible from pure Mg. Yet, due to their alloying elements, such as rare-earths or aluminum, they are either not economical or biocompatible. Here we present a new rare-earth and aluminum-free magnesium-based alloy, with trace amounts of Zn, Ca, and Mn (≈ 2% by wt.). We show that the dilute alloy exhibits outstanding high strength and high ductility compared to other dilute Mg alloys. By direct comparison with annealed material of the same chemistry and using transmission electron microscopy (TEM), high-resolution TEM (HR-TEM) and atom probe tomography analyses, we show that the high strength can be attributed to a number of very fine, Zn/Ca-containing nanoscale precipitates, along with ultra-fine grains. These findings show that forming a hierarchy of nanometer precipitates from just miniscule amounts of solute can invoke simultaneous high strength and ductility, producing an affordable, biocompatible Mg alloy.

Degradation kinetics and surface properties of bioceramic hydroxyapatite coated AZ31 magnesium alloys for biomedical applications

Controlling degradation and improving the biocompatibility of AZ31 magnesium alloys is under continuous research for its practical biomedical applications. Here we have applied a bio-ceramic, hydroxyapatite (HAp), on AZ31 through radio frequency sputtering. The degradation analysis was investigated in SBF (simulated body fluid) for 48 days through weight loss of sample and release of Mg2+ ions by atomic absorption spectroscopy. XRD and elemental analysis confirmed the successful coating of HAp on AZ31. AZ31 was found to be hydrophilic, which became hydrophobic after sputtering. The degradation kinetics was modeled with a single exponential expression and both the weight loss and release of Mg2+ ions data of sample agreed with the same rate constant. The rate of degradation of bare AZ31 was decreased to 20% for the 9 h coated AZ31.

Electroformation of Coatings Modified with Silver on Magnesium Alloys for Biomedical Applications

Fil: Loperena, Ana Paula. Universidad Nacional del Sur. Departamento de Ingenieria Quimica. Instituto de Ingenieria Electroquimica y Corrosion; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina

Investigation of the Oxidation Mechanism of Dopamine Functionalization in an AZ31 Magnesium Alloy for Biomedical Applications

Implant design and functionalization are under significant investigation for their ability to enhance bone-implant grafting and, thus, to provide mechanical stability for the device during the healing process. In this area, biomimetic functionalizing polymers like dopamine have been proven to be able to improve the biocompatibility of the material. In this work, the dip coating of dopamine on the surface of the magnesium alloy AZ31 is investigated to determine the effects of oxygen on the functionalization of the material. Two different conditions are applied during the dip coating process: (1) The absence of oxygen in the solution and (2) continuous oxygenation of the solution. Energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) are used to analyze the composition of the formed layers, and the deposition rate on the substrate is determined by molecular dynamic simulation. Electrochemical analysis and cell cultivation are performed to determine the corrosion resistance and cell’s behavior, respectively. The high oxygen concentration in the dopamine solution promotes a homogeneous and smooth coating with a drastic increase of the deposition rate. Also, the addition of oxygen into the dip coating process increases the corrosion resistance of the material.

Mechanical and degradation properties of zinc adopted magnesium alloys for biomedical application

The demand for short-term degradable implant in bone fixation applications is growing steadily due to the aging population worldwide. Degradable implants have the advantage that the second surgery for implant removal is not required. Magnesium is one of the best candidates because it is biodegradable, physiologically compatible and even stimulates bone reconstruction. However, the high degradation rate of pure magnesium in human body fluids may prevent its wider application. In this study, Zinc (Zn) was added in magnesium (Mg) to improve its properties. The effects of five different weight percentage of Zinc (2%, 4%, 6%, 8%, 10%) were investigated. The microstructure and mechanical properties evolution of the alloys were characterized and evaluated using optical microscopy, Scanning Electron Microscope (SEM), tensile test and Vickers hardness test, while degradation behavior was examined using electrochemical corrosion test. The binary Mg-Zn cast alloy with 6 wt. % zinc content (labeled as Mg-6Zn) shows optimum mechanical strength with slowest degradation rate.

Hydrothermal deposition of high strength calcium phosphate coatings on magnesium alloy for biomedical applications

Magnesium and Mg-alloys are suitable replacement to metallic implants (Titanium, stainless steel, Co-Cr alloys) in terms of stress shielding effect and repeated surgery requirement. However, the only hindrance in their successful use as biodegradable orthopedic implants is their high corrosion rates in physiological environment. Thus, in present study, we developed the single step hydrothermal process to deposit bioactive coatings that may lower the corrosion rate. Highly crystalline, cytocompatible, bioresorbable and high strength monetite (CaHPO4) coating successfully produced on Ca-containing Mg-alloy via hydrothermal process. Deposition parameters have significant influence on coatings morphology and degree of crystallinity. XRD pattern indicates sharp, intense and well-defined peaks of monetite along with minor peaks of brucite and spinel phases. SEM study reveals that compact and defects free coatings were deposited at 100 °C. FTIR analysis showed all characteristic peaks that confirms the presence of monetite. Corrosion behavior of coated and uncoated specimen were analyzed using potentiodynamic polarization scan in simulated body fluid (SBF) at 37 °C. Calcium phosphate (CaP) coating significantly improve the degradation rate of Mg-alloy. Corrosion rate was 80% lower in CaP coated Mg-alloy specimens than bare Mg-alloy. Adhesion strength of coatings was determined using lap shear test demonstrating a cohesive failure at 21.89 MPa stress. Furthermore, cytotoxicity of coated and uncoated alloy was assessed by using Alamar Blue (AB) assay on NIH3T3 mouse fibroblast cell line for 9 days indicate no significant difference in proliferation of cells for CaP coated Mg-alloy and positive control. These results suggest that hydrothermal method reported here can potentially be used to deposit compact, highly crystalline, bioresorbable, cytocompatible and protective coatings with high adhesion strength on intricate geometries for degradable implant applications.