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Magnesium and Its Alloys as Biodegradable Implants

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Biomaterials".

Deadline for manuscript submissions: closed (10 October 2022) | Viewed by 14860

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Special Issue Editors

Dr. Mirco Peron

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Department of Information Systems, Supply Chain Management & Decision Support, NEOMA Business School, 1 Rue du Maréchal Juin, 76130 Mont-Saint-Aignan, France
Interests: supply chain management; digital supply chain management; circular economy; hydrogen supply chain; decision support systems; additive manufacturing; Industry 4.0
Special Issues, Collections and Topics in MDPI journals

Dr. Bertolini Rachele

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Department of Industrial Engineering, University of Padova, Padova, Italy
Interests: machining; surface integrity; mechanical behavior of materials; corrosion; wear

Special Issue Information

Dear Colleagues,

Recently, magnesium has gained increasing interest for temporary biomedical applications, such as fixators and vascular stents, due to its high biomechanical compatibility with human bones. Specifically, its elastic modulus compatible with that of natural bone minimizes the risk of stress shielding and its corrosion process does not release toxic products. However, the accelerated corrosion of pure Mg hampers its usability in clinical applications because mechanical failure of the implant is prone to occur before the tissue has recovered and, during corrosion, hydrogen gas is produced at rates beyond the level that bone tissue is able to accommodate, ultimately causing severe host tissue damage. To solve this limitation, researchers have investigated different solutions, such as the addition of alloying elements, microstructure modifications (e.g., through severe plastic deformation techniques) and surface modifications (e.g., the application of coatings).

This Special Issue aims to present the latest innovative strategies to overcome the current limitations and their impacts on corrosion resistance (in vitro and/or in vivo), osseointegration properties, and mechanical properties, especially in the corrosive environment (e.g., stress corrosion cracking and corrosion fatigue).

Dr. Mirco Peron
Dr. Bertolini Rachele
Guest Editors

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Keywords

Magnesium and its alloys
Biodegradable materials
Coatings
Severe plastic deformation techniques
Surface modification
Alloying
Corrosion resistance
Stress corrosion cracking
Corrosion fatigue

Published Papers (7 papers)

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Research

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24 pages, 3728 KiB

Open AccessEditor’s ChoiceArticle

Effects of Altering Magnesium Metal Surfaces on Degradation In Vitro and In Vivo during Peripheral Nerve Regeneration

by Rigwed Tatu, Leon G. White, Yeoheung Yun, Tracy Hopkins, Xiaoxian An, Ahmed Ashraf, Kevin J. Little, Meir Hershcovitch, David B. Hom and Sarah Pixley

Materials 2023, 16(3), 1195; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16031195 - 30 Jan 2023

Cited by 3 | Viewed by 1893

Abstract

In vivo use of biodegradable magnesium (Mg) metal can be plagued by too rapid a degradation rate that removes metal support before physiological function is repaired. To advance the use of Mg biomedical implants, the degradation rate may need to be adjusted. We previously demonstrated that pure Mg filaments used in a nerve repair scaffold were compatible with regenerating peripheral nerve tissues, reduced inflammation, and improved axonal numbers across a short—but not long—gap in sciatic nerves in rats. To determine if the repair of longer gaps would be improved by a slower Mg degradation rate, we tested, in vitro and in vivo, the effects of Mg filament polishing followed by anodization using plasma electrolytic oxidation (PEO) with non-toxic electrolytes. Polishing removed oxidation products from the surface of as-received (unpolished) filaments, exposed more Mg on the surface, produced a smoother surface, slowed in vitro Mg degradation over four weeks after immersion in a physiological solution, and improved attachment of cultured epithelial cells. In vivo, treated Mg filaments were used to repair longer (15 mm) injury gaps in adult rat sciatic nerves after placement inside hollow poly (caprolactone) nerve conduits. The addition of single Mg or control titanium filaments was compared to empty conduits (negative control) and isografts (nerves from donor rats, positive control). After six weeks in vivo, live animal imaging with micro computed tomography (micro-CT) showed that Mg metal degradation rates were slowed by polishing vs. as-received Mg, but not by anodization, which introduced greater variability. After 14 weeks in vivo, functional return was seen only with isograft controls. However, within Mg filament groups, the amount of axonal growth across the injury site was improved with slower Mg degradation rates. Thus, anodization slowed degradation in vitro but not in vivo, and degradation rates do affect nerve regeneration. Full article

(This article belongs to the Special Issue Magnesium and Its Alloys as Biodegradable Implants)

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14 pages, 3015 KiB

Open AccessArticle

Development of Biocompatible Bulk MgZnCa Metallic Glass with Very High Corrosion Resistance in Simulated Body Fluid

by Shi Jie Bryan Bin, Kai Soon Fong, Beng Wah Chua and Manoj Gupta

Materials 2022, 15(24), 8989; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15248989 - 16 Dec 2022

Cited by 2 | Viewed by 1605

Abstract

Magnesium-zinc-calcium (Mg-Zn-Ca) alloys as a biomaterial have attracted much attention recently, owing to their excellent biocompatibility, similar mechanical properties to natural bone, and biodegradable properties. Despite the numerous advantages of MgZnCa alloys, the rapid degradation of magnesium proved challenging as the implant in unable to retain its structural integrity for a sufficient duration of time. For metallic glasses, the capability to produce a bulk sample that is sufficiently large for useful applications have been far less successful owing to challenging processing parameters that are required for rapid cooling. In this study, Mg₆₅Zn₃₀Ca₅ melt-spun ribbons were produced using melt-spinning followed by spark plasma sintering under high pressure (60 MPa) at different temperatures (130–170 °C) to provide an insight into the consolidation, mechanical, and corrosion behavior. Microstructural interfaces were characterized using scanning electron microscopy while the thermal stability of the amorphous phase was characterized using differential scanning calorimetry and X-ray diffraction. Here, pellets with 10 mm diameter and 10 mm height with a complete amorphous structure were achieved at a sintering temperature of 150 °C with densification as high at ~98%. Sintering at higher temperatures, while achieving higher densification, resulted in the presence of nano-crystallites. The mechanical properties were characterized using microhardness and compression tests. The hardness values of the sintered products were relatively higher to those containing crystallite phases while the ultimate compressive strength increased with increasing sintering temperature. Bio-corrosion properties were characterized via electrochemical testing with PBS as the electrolyte at 37 °C. The corrosion results suggest that the sintered samples have a significantly improved corrosion resistance as compared to as-cast samples. More notably, SPS150 (samples sintered at 150 °C) exhibited the best corrosion resistance (35× compared to as-cast in the context of corrosion current density), owing to its single-phase amorphous nature. This study clearly shows the potential of spark plasma sintering in consolidating amorphous ribbons to near-full density bulk pellets with high corrosion resistance for bio-applications. Full article

(This article belongs to the Special Issue Magnesium and Its Alloys as Biodegradable Implants)

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14 pages, 11534 KiB

Open AccessArticle

Bone Remodeling Interaction with Magnesium Alloy Implants Studied by SEM and EDX

by Alexey Drobyshev, Alexander Komissarov, Nikolay Redko, Zaira Gurganchova, Eugene S. Statnik, Viacheslav Bazhenov, Iuliia Sadykova, Andrey Miterev, Igor Romanenko and Oleg Yanushevich

Materials 2022, 15(21), 7529; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15217529 - 27 Oct 2022

Cited by 4 | Viewed by 1931

Abstract

The development direction of bioresorbable fixing structures is currently very relevant because it corresponds to the priority areas in worldwide biotechnology development. Magnesium (Mg)-based alloys are gaining high levels of attention due to their promising potential use as the basis for fixating structures. These alloys can be an alternative to non-degradable metal implants in orthopedics, maxillofacial surgery, neurosurgery, and veterinary medicine. In our study, we formulated a Mg-2Zn-2Ga alloy, prepared pins, and analyzed their biodegradation level based on SEM (scanning electron microscopy) and EDX (energy-dispersive X-ray analysis) after carrying out an experimental study on rats. We assessed the resorption parameters 1, 3, and 6 months after surgery. In general, the biodegradation process was characterized by the systematic development of newly formed bone tissue. Our results showed that Mg-2Zn-2Ga magnesium alloys are suitable for clinical applications. Full article

(This article belongs to the Special Issue Magnesium and Its Alloys as Biodegradable Implants)

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31 pages, 13270 KiB

Open AccessArticle

Influence of Ultrafine-Grained Microstructure and Texture Evolution of ECAPed ZK30 Magnesium Alloy on the Corrosion Behavior in Different Corrosive Agents

by Abdulrahman I. Alateyah, Majed O. Alawad, Talal A. Aljohani and Waleed H. El-Garaihy

Materials 2022, 15(16), 5515; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15165515 - 11 Aug 2022

Cited by 20 | Viewed by 1425

Abstract

Magnesium-Zinc-Zirconium (Mg-Zn-Zr) alloys have caught considerable attention in medical applications where biodegradability is critical. The combination of their good biocompatibility, improved strength, and low cytotoxicity makes them great candidates for medical implants. This research investigation is focused on providing further insight into the effects of equal channel angular processing (ECAP) on the corrosion behavior, microstructure evolution, and mechanical properties of a biodegradable ZK30 alloy. Billets of Mg-3Zn-0.6 Zr (ZK30) alloy were processed through ECAP up to 4 passes of route Bc (rotating the billets 90° in the same direction between the subsequent passes) at 250 °C. Electron back-scatter diffraction (EBSD) was utilized to investigate the microstructural evolution as well as the crystallographic texture. Several electrochemical measurements were carried out on both a simulated body fluid and a 3.5% sodium chloride (NaCl) solution. Mechanical properties such as Vicker’s hardness and tensile properties were also assessed. The as-annealed (AA) microstructure was dominated by equiaxed coarse recrystallized grains with an average grain size of 26.69 µm. After processing, a geometric grain subdivision took place due to the severe plastic deformation. Processed samples were characterized by grain refinement and high density of substructures. The 4-passes sample experienced a reduction in the grain size by 92.8% compared with its AA counterpart. The fraction of high-angle grain boundaries increased significantly after 4-passes compared to the 1-pass processed sample. With regards to the crystallographic texture, the AA condition had its {0001} basal planes mostly oriented parallel to the transversal direction. On the other hand, ECAP processing resulted in crystallographic texture changes, such as the shifting of the ZK30 shear plane to be aligned at 45° relative to the extrusion direction (ED). Furthermore, the maximum texture intensity was reduced from 14 times random (AA billets) to 8 times random after ECAP processing through 4-passes. The corrosion rate of the 4-passes sample was tremendously reduced by 99% and 45.25% compared with its AA counterpart in the simulated body fluid and the NaCl solution, respectively. The pitting corrosion resistance of ZK30 showed notable improvements in the simulated body fluid by 471.66% and 352% during processing through 1-pass and 4-passes, respectively, compared with the 3.5% NaCl findings. Finally, significant improvements in the tensile strength, hardness, and ductility were also achieved. Full article

(This article belongs to the Special Issue Magnesium and Its Alloys as Biodegradable Implants)

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20 pages, 7270 KiB

Open AccessArticle

Monitoring Dynamic Recrystallisation in Bioresorbable Alloy Mg-1Zn-0.2Ca by Means of an In Situ Acoustic Emission Technique

by Dmitry Merson, Mikhail Linderov, Alexander Brilevsky, Alexey Danyuk and Alexei Vinogradov

Materials 2022, 15(1), 328; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15010328 - 03 Jan 2022

Cited by 7 | Viewed by 1419

Abstract

The tensile behaviour of the biocompatible alloy Mg-1Zn-0.2Ca (in wt.%) in the fine-grained state, obtained by severe plastic deformation via multiaxial isothermal forging, has been investigated in a wide range of temperatures (20 ÷ 300) °C and strain rates (5 × 10⁻⁴ ÷ 2 × 10⁻²) s⁻¹ with the measurements of acoustic emission (AE). The dependences of mechanical properties, including the yield stress, ultimate strength, ductility, and the strain-hardening rate, on the test temperature and strain rate, were obtained and discussed. It is shown for the first time that an acoustic emission method is an effective tool for in situ monitoring of the dynamic recrystallisation (DRX) process. The specific behaviour of the acoustic emission spectral density reflected by its median frequency as a function of strain at various temperatures can serve as an indicator of the DRX process’s completeness. Full article

(This article belongs to the Special Issue Magnesium and Its Alloys as Biodegradable Implants)

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14 pages, 2767 KiB

Open AccessEditor’s ChoiceArticle

Microstructural and Corrosion Properties of Hydroxyapatite Containing PEO Coating Produced on AZ31 Mg Alloy

by Luca Pezzato, Katya Brunelli, Stefano Diodati, Mirko Pigato, Massimiliano Bonesso and Manuele Dabalà

Materials 2021, 14(6), 1531; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14061531 - 21 Mar 2021

Cited by 38 | Viewed by 2506

Abstract

In this work, the composition of an electrolyte was selected and optimized to induce the formation of hydroxyapatite during Plasma electrolytic oxidation (PEO) treatment on an AZ31 alloy for application in bioabsorbable implants. In detail, the PEO process, called PEO-BIO (Plasma Electrolytic Oxidation-Biocompatible), was performed using a silicate-phosphate-based electrolyte with the addition of calcium oxide in direct-current mode using high current densities and short treatment times. For comparison, a known PEO process for producing anticorrosive coatings, called standard, was applied on the same alloy. The coatings were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and XPS analyses. The corrosion performance was evaluated in simulated body fluid (SBF) at 37 °C. The coating produced on the PEO-BIO sample was porous and thicker than the standard PEO one, with zones enriched in Ca and P. The XRD analysis showed the formation of hydroxyapatite and calcium oxides in addition to magnesium-silicon oxide and magnesium oxide in the PEO-BIO sample. The corrosion resistance of PEO-BIO sample was comparable with that of a traditional PEO treated sample, and higher than that of the untreated alloy. Full article

(This article belongs to the Special Issue Magnesium and Its Alloys as Biodegradable Implants)

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Review

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43 pages, 19817 KiB

Open AccessReview

Attaining High Functional Performance in Biodegradable Mg-Alloys: An Overview of Challenges and Prospects for the Mg-Zn-Ca System

by Alexei Vinogradov, Evgeniy Merson, Pavel Myagkikh, Mikhail Linderov, Alexandr Brilevsky and Dmitry Merson

Materials 2023, 16(3), 1324; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16031324 - 03 Feb 2023

Cited by 11 | Viewed by 3074

Abstract

This article presents a concise overview of modern achievements and existing knowledge gaps in the area of biodegradable magnesium alloys. Hundreds of Mg-based alloys have been proposed as candidates for temporary implants, and this number tends to increase day by day. Therefore, while reviewing common aspects of research in this field, we confine ourselves primarily to the popular Mg-Zn-Ca system, taken as a representative example. Over the last decades, research activities in this area have grown enormously and have produced many exciting results. Aiming at highlighting the areas where research efforts are still scarce, we review the state-of-the-art processing techniques and summarize the functional properties attained via a wide variety of processing routes devised towards achieving a desired properties profile, including the mechanical response in terms of strength, ductility, and fatigue resistance paired with biocompatibility and bio-corrosion resistance or controlled degradability. We pay keen attention to a summary of corrosion properties and mechano-chemical interactions between an aggressive environment and loaded Mg-based structures, resulting in stress corrosion cracking and premature corrosion fatigue failures. The polemic issues and challenges practitioners face in their laboratory research are identified and discussed. Full article

(This article belongs to the Special Issue Magnesium and Its Alloys as Biodegradable Implants)

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