Magnesium-based Biomaterials Research Articles

Hydroxyapatite Reinforced Magnesium Alloy Composites Using the Ultrasonic-Assisted Rheo-Squeeze Casting Technique: Microstructural and Mechanical Performance Evaluation for Bone Fixture Applications

Magnesium-based biomaterials have recently been in the research spotlight in the field of biomedical engineering owing to their properties, such as density and biocompatibility that closely align with those of human bone. However, poor strength and rapid degradation impede their application as bone support fixtures. The present research aims to tailor the properties of Mg by using a novel ultrasonic-assisted rheo-squeeze casting approach. To satisfy the demand, pure Mg (Mg), MHA (Mg/5%HA), MZHA (Mg-1%Zn/5%HA/), and MSHA (Mg-1%Sn/5%HA) were fabricated, and various mechanical tests were conducted to assess the composite’s mechanical properties, including its microhardness, tensile strength, compressive strength, flexural strength, and impact strength. The microstructural and fractured morphology of the composites was examined by scanning electron microscopy (SEM), whereas their elemental composition was analyzed by field emission scanning electron microscopy (FESEM) equipped with elemental mapping. Comparing the MZHA, MHA, and pure Mg samples, the mechanical behavior of MSHA is significantly superior. This is due to composites containing Sn that possess finer-grained materials, which act as barriers to dislocation motion while increasing the strength of the materials. From the observed results, there is a significant improvement in the microhardness of MSHA of 64.5% when compared to that of pure Mg, and 42.7% compared to MHA. Furthermore, MSHA composites possess noticeable enhancements in tensile and compression performance of 80.8% and 58.3%, respectively, and 19% and 22.4% compared to MHA. Additionally, the impact and flexural performance of MSHA composites exhibit higher performance (41% and 42%) than pure Mg and 8% and 7% against the MHA composite.

Challenges and Pitfalls of Research Designs Involving Magnesium-Based Biomaterials: An Overview.

Magnesium-based biomaterials hold remarkable promise for various clinical applications, offering advantages such as reduced stress-shielding and enhanced bone strengthening and vascular remodeling compared to traditional materials. However, ensuring the quality of preclinical research is crucial for the development of these implants. To achieve implant success, an understanding of the cellular responses post-implantation, proper model selection, and good study design are crucial. There are several challenges to reaching a safe and effective translation of laboratory findings into clinical practice. The utilization of Mg-based biomedical devices eliminates the need for biomaterial removal surgery post-healing and mitigates adverse effects associated with permanent biomaterial implantation. However, the high corrosion rate of Mg-based implants poses challenges such as unexpected degradation, structural failure, hydrogen evolution, alkalization, and cytotoxicity. The biocompatibility and degradability of materials based on magnesium have been studied by many researchers in vitro; however, evaluations addressing the impact of the material in vivo still need to be improved. Several animal models, including rats, rabbits, dogs, and pigs, have been explored to assess the potential of magnesium-based materials. Moreover, strategies such as alloying and coating have been identified to enhance the degradation rate of magnesium-based materials in vivo to transform these challenges into opportunities. This review aims to explore the utilization of Mg implants across various biomedical applications within cellular (in vitro) and animal (in vivo) models.

The Manufacturing Process and Corrosion Properties of Magnesium Matrix Composites: A Review

Magnesium-based biomaterials are a new generation of biodegradable metals that are playing a major role in the development of future implant materials. Magnesium-based materials can corrode too rapidly during physiological conditions and lose their usefulness before bones heal. This review aims to provide a comprehensive overview of the selection of suitable matrix and reinforcing materials as well as suitable process techniques to achieve better corrosion resistance targeted for dental implant applications. It also discusses the advantages and disadvantages of testing methods and corrosion media commonly used for biomedical applications. Specific search strategies are carried out in electronic databases: Springer, Pubmed, and Sciencedirect as well as google without limiting years. Papers are selected after reviewing their title, abstract, and full text. Then study the objectives, criteria, methods, and results. Based on the available literature, we can conclude that for magnesium-based composite matrices it is preferable to use commercially available Mg AZ91D alloys to investigate their corrosion behavior in vitro and in vivo environments. While for the composite reinforcement, bioceramic materials can be used, including Hydroxyapatite (HA) added with Zirconia ceramics (ZrO2) or Titanium metal oxide (TiO2). Furthermore, the process of making ceramic composites uses powder metallurgy (PM) and squeeze casting methods. Then, corrosive testing can use the commonly used electrochemical methods, namely Potentiodynamic Polarization (PDP) and Electrochemical Impedance Spectroscopy (EIS) with corrosive SBF media.

INFLUENCE OF MG-CYLINDERS ON BONE AND CARTILAGE IN OSTEOARTHRITIS

There are no efficient treatment options for osteoarthritis (OA) that delay further progression. Besides osteoinduction, there is growing evidence of also anti-inflammatory, angiogenetic and neuroprotective effects of biodegradable magnesium-based biomaterials. Their use for the treatment of cartilage lesions in contrast is not well-evaluated yet.Mg-cylinders were analysed in an in vitro and in vivo OA model. In vitro, SCP-1 stem cell line was analysed under inflammatory conditions and Mg-impact. In vivo, small Mg- and WE43 alloy-cylinders (1mm × 0,5mm) were implanted into the subchondral bone of the knee joint of 24 NZW rabbits after establishment of OA. As control, another 12 rabbits received only drill-holes. µCT-scan were performed and assessed for changes in bone volume and density. After euthanasia, cartilage was evaluated macroscopically and histologically after Safranin-O-staining. Furthermore, staining with CD271 directed antibody was performed to assess neuro-reactivity.In vitro, an increased gene expression of extracellular matrix proteins as collagen II or aggrecan even under inflammatory conditions was observed under Mg-impact. In vivo, µCT evaluation revealed twice-elevated values for bone volume in femoral condyles with Mg-cylinders compared to controls while density remained unchanged. Cartilage showed no significant differences between the groups. Mg- and WE-samples showed significantly lower levels of CD271+ cells in the cartilage and bone of the operated joints than in non-operated joints, which was not the case in the Drilling-group. Furthermore, bone in operated knees of Drilling-group showed a strong trend to an increase in CD271+ cells compared to both Cylinder-groups. Counting of CD271+ vessels revealed that this difference was attributable to a higher amount of these vessels.The in vitro results indicate a potential cartilage regenerative activity of the degradable Mg-based material. While so far there was no positive effect on the cartilage itself in vivo, implantation of Mg-cylinders seemed to reduce pain-mediating vessels.Acknowledgements: This work is funded by the German Research Foundation (DFG, project number 404534760). We thank Björn Wiese for production of the cylinders.

The development of magnesium-based biomaterials in bone tissue engineering: A review.

Bone regeneration is a vital clinical challenge in massive or complicated bone defects. Recently, bone tissue engineering has come to the fore to meet the demand for bone repair with various innovative materials. However, the reported materials usually cannot satisfy the requirements, such as ideal mechanical and osteogenic properties, as well as biocompatibility at the same time. Mg-based biomaterials have considerable potential in bone tissue engineering owing to their excellent mechanical strength and biosafety. Moreover, the biocompatibility and osteogenic activity of Mg-based biomaterials have been the research focuses in recent years. The main limitation faced in the applications of Mg-based biomaterials is rapid degradation, which can produce excessive Mg2+ and hydrogen, affecting the healing of the bone defect. In order to overcome the limitations, researchers have explored several ways to improve the properties of Mg-based biomaterials, including alloying, surface modification with coatings, and synthesizing other composite materials to control the degradation rate upon implantation. This article reviewed the osteogenic mechanism and requirement for appropriate degradation rate and focused on current progress in the biomedical use of Mg-based biomaterials to inspire more clinical applications of Mg in bone regeneration in the future.

Bioresorbable magnesium-based alloys containing strontium doped nanohydroxyapatite promotes bone healing in critical sized bone defect in rat femur shaft

Magnesium-based biomaterials have been in extensive research for orthopedic applications for decades due to their optimal mechanical features and osteopromotive nature; nevertheless, rapid degradation restricts their clinical applicability. In this study, pristine magnesium was purified (P-Mg) using a melt self-purification approach and reinforced using indigenously synthesized nanohydroxyapatite (HAP, 0.6 wt.%) and strontium substituted nanohydroxyapatite (SrHAP, 0.6 wt.%) using a low-cost stir assisted squeeze casting method to control their degradation rate. Using electron back-scattered diffraction (EBSD) and X-ray diffraction (XRD) examinations, all casted materials were carefully evaluated for microstructure and phase analysis. Mechanical characteristics, in vitro degradation, and in vitro biocompatibility with murine pre-osteoblasts were also tested on the fabricated alloys. For in vivo examination of bone formation, osteointegration, and degradation rate, the magnesium-based alloys were fabricated as small cylindrical pins with a diameter of 2.7 mm and a height of 2 mm. The pins were implanted in a critical-sized defect in a rat femur shaft (2.7 mm diameter and 2 mm depth) for 8 weeks and evaluated by micro-CT and histological evaluation for bone growth and osteointegration. When compared to P-Mg and P-MgHAP, micro-CT and histological analyses revealed that the P-MgSrHAP group had the highest bone formation towards the periphery of the implant and hence maximum osteointegration. When the removed pins from the bone defect were analyzed using GIXRD, they displayed hydroxyapatite peaks that were consistent with bio-integration. For P-Mg, P-MgHAP, and P-MgSrHAP 8 weeks after implantation , in vivo degradation rates derived from micro-CT were around 0.6 mm/year, 0.5 mm/year, and 0.1 mm/year, respectively. Finally, P-MgSrHAP possesses the requisite degradation rate as well as sufficient mechanical and biological properties, indicating that it has the potential to be used in the development/fabrication of biodegradable bioactive orthopaedic implants.

Electrochemical Short-Time Testing Method for Simulating the Degradation Behavior of Magnesium-Based Biomaterials

In regenerative medicine, degradable, magnesium-based biomaterials represent a promising material class. The low corrosion resistance typical for magnesium is advantageous for this application since the entire implant degrades in the presence of the aqueous body fluids after fulfilling the intended function, making a second operation for implant removal obsolete. To ensure sufficient stability within the functional phase, the degradation behavior must be known for months. In order to reduce time and costs for these long-time investigations, an electrochemical short-time testing method is developed and validated, accelerating the dissolution process of a magnesium alloy with and without surface modification based on galvanostatic anodic polarization, enabling a simulation of longer immersion times. During anodic polarization, the hydrogen gas formed by the corrosion process increases linearly. Moreover, the gas volume shows a linear relationship to the dissolving mass, enabling a defined dissolution of magnesium. As a starting point, corrosion rates of both variants from three-week immersion tests are used. A simplified relationship between the current density and the dissolution rate, determined experimentally, is used to design the experiments. Ex situ µ-computed tomography scans are performed to compare the degradation morphologies of both test strategies. The results demonstrate that a simulation of the degradation rates and, hence, considerable time saving based on galvanostatic anodic polarization is possible. Since the method is accompanied by a changed degradation morphology, it is suitable for a worst-case estimation allowing the exclusion of new, unsuitable magnesium systems before subsequent preclinical studies.

Synthesis, microstructure and biodegradation behavior of MgO-TiO2-PCL nanocomposite coatings on the surface of magnesium-based biomaterials

In this study, a magnesium oxide-titanium dioxide (MgO-TiO2) nanocomposite film was successfully applied to pure magnesium (Mg) surface using the plasma electrolytic oxidation (PEO) technique in an electrolyte solution containing TiO2 nanoparticles. A uniform top-layer polycaprolactone (PCL) coating was eventually formed on the PEO-treated Mg through a dip-coating process. The results indicated that the porous nature of the PEO-coated samples could not provide the desired corrosion resistance in simulated body fluid (SBF). However, the deposition of the top-layer PCL coating (utilizing 8wt% PCL) over the MgO-TiO2 nanocomposite coating greatly improved the corrosion resistance of the Mg substrate. The proposed PCL top-layer coated MgO-TiO2 nanocomposite film could be considered as a promising candidate for the surface modification of Mg-based biodegradable implants. Due to the microstructural and macrostructural porous nature of the PEO film, this coating can be further used on the surface of biodegradable implants not only to control the degradation rate but also to deliver therapeutic molecules.

In silico modelling of the corrosion of biodegradable magnesium-based biomaterials: modelling approaches, validation and future perspectives.

ABSTRACTMetallic biomedical implants based on magnesium, zinc and iron alloys have emerged as bioresorbable alternatives to permanent orthopaedic implants over the last two decades. The corrosion rate of biodegradable metals plays a critical role in controlling the compatibility and functionality of the device in vivo. The broader adoption of biodegradable metals in orthopaedic applications depends on developing in vitro methods that accurately predict the biodegradation behaviour in vivo. However, the physiological environment is a highly complex corrosion environment to replicate in the laboratory, making the in vitro-to-in vivo translation of results very challenging. Accordingly, the results from in vitro corrosion tests fail to provide a complete schema of the biodegradation behaviour of the metal in vivo. In silico approach based on computer simulations aim to bridge the observed differences between experiments performed in vitro and vivo. A critical review of the state-of-the-art of computational modelling techniques for predicting the corrosion behaviour of magnesium alloy as a biodegradable metal is presented.

Magnesium Promotes the Regeneration of the Peripheral Nerve.

Peripheral nerve injury is a common complication in trauma, and regeneration and function recovery are clinical challenges. It is indispensable to find a suitable material to promote peripheral nerve regeneration due to the limited capacity of peripheral nerve regeneration, which is not an easy task to design a material with good biocompatibility, appropriate degradability. Magnesium has captured increasing attention during the past years as suitable materials. However, there are little types of research on magnesium promoting peripheral nerve regeneration. In this review, we conclude the possible mechanism of magnesium ion promoting peripheral nerve regeneration and the properties and application of different kinds of magnesium-based biomaterials, such as magnesium filaments, magnesium alloys, and others, in which we found some shortcomings and challenges. So, magnesium can promote peripheral nerve regeneration with both challenge and potential.

Controlled release of hydrogen by implantation of magnesium induces P53-mediated tumor cells apoptosis

Hydrogen has been used to suppress tumor growth with considerable efficacy. Inhalation of hydrogen gas and oral ingestion of hydrogen-rich saline are two common systemic routes of hydrogen administration. We have developed a topical delivery method of hydrogen at targeted sites through the degradation of magnesium-based biomaterials. However, the underlying mechanism of hydrogen's role in cancer treatment remains ambiguous. Here, we investigate the mechanism of tumor cell apoptosis triggered by the hydrogen released from magnesium-based biomaterials. We find that the localized release of hydrogen increases the expression level of P53 tumor suppressor proteins, as demonstrated by the in vitro RNA sequencing and protein expression analysis. Then, the P53 proteins disrupt the membrane potential of mitochondria, activate autophagy, suppress the reactive oxygen species in cancer cells, and finally result in tumor suppression. The anti-tumor efficacy of magnesium-based biomaterials is further validated in vivo by inserting magnesium wire into the subcutaneous tumor in a mouse. We also discovered that the minimal hydrogen concentration from magnesium wires to trigger substantial tumor apoptosis is 91.2 μL/mm3 per day, which is much lower than that required for hydrogen inhalation. Taken together, these findings reveal the release of H2 from magnesium-based biomaterial exerts its anti-tumoral activity by activating the P53-mediated lysosome-mitochondria apoptosis signaling pathway, which strengthens the therapeutic potential of this biomaterial as localized anti-tumor treatment.

Magnesium-based biomaterials as emerging agents for bone repair and regeneration: from mechanism to application

Magnesium (Mg) is the fourth most abundant element in the human body and is important in terms of specific osteogenesis functions. Here, we provide a comprehensive review of the use of magnesium-based biomaterials (MBs) in bone reconstruction. We review the history of MBs and their excellent biocompatibility, biodegradability and osteopromotive properties, highlighting them as candidates for a new generation of biodegradable orthopedic implants. In particular, the results reported in the field-specific literature (280 articles) in recent decades are dissected with respect to the extensive variety of MBs for orthopedic applications, including Mg/Mg alloys, bioglasses, bioceramics, and polymer materials. We also summarize the osteogenic mechanism of MBs, including a detailed section on the physiological process, namely, the enhanced osteogenesis, promotion of osteoblast adhesion and motility, immunomodulation, and enhanced angiogenesis. Moreover, the merits and limitations of current bone grafts and substitutes are compared. The objective of this review is to reveal the strong potential of MBs for their use as agents in bone repair and regeneration and to highlight issues that impede their clinical translation. Finally, the development and challenges of MBs for transplanted orthopedic materials are discussed.

An in-vitro evaluation study on the effects of surface modification via physical vapor deposition on the degradation rates of magnesium-based biomaterials

Magnesium (Mg) metal as a degradable biomaterial is under extensive research, but its high corrosion rate limits its application. In this study, an attempt has been made to increase the viability of pure Mg as a degradable biomaterial for cardiovascular applications with surface modification of pure Mg. Pure Iron (Fe) and hydroxyapatite (HaP) were coated on pure Mg substrates. Analysis of their mechanical and biological characteristics was made. The tensile strength for pure Mg was 80 MPa, Fe and HaP coating on Mg increased the tensile strength values by approximately 45% and 21%, respectively. A maximum degradation rate of about 5.4 mm/year was observed for pure Mg. HaP coating decreased the degradation rate by almost 73%. However, galvanic corrosion caused a sixfold rise in the degradation rate for Fe coating. Hemolysis study indicated all three substrates as non-hemolytic, and the cell viability from MTT cytotoxic assay for uncoated, Fe and HaP coated substrates are 96.24%, 94.8% and 97.13%, respectively. Pure Mg is non-hemolytic and non-cytotoxic, coating Fe and HaP does not affect biological properties but improved the mechanical strength. This work, therefore, establishes altered Mg substrates as effective material for cardiovascular applications.

Toward Tailoring the Degradation Rate of Magnesium-Based Biomaterials for Various Medical Applications: Assessing Corrosion, Cytocompatibility and Immunological Effects.

Magnesium (Mg)-based biomaterials hold considerable promise for applications in regenerative medicine. However, the degradation of Mg needs to be reduced to control toxicity caused by its rapid natural corrosion. In the process of developing new Mg alloys with various surface modifications, an efficient assessment of the relevant properties is essential. In the present study, a WE43 Mg alloy with a plasma electrolytic oxidation (PEO)-generated surface was investigated. Surface microstructure, hydrogen gas evolution in immersion tests and cytocompatibility were assessed. In addition, a novel in vitro immunological test using primary human lymphocytes was introduced. On PEO-treated WE43, a larger number of pores and microcracks, as well as increased roughness, were observed compared to untreated WE43. Hydrogen gas evolution after two weeks was reduced by 40.7% through PEO treatment, indicating a significantly reduced corrosion rate. In contrast to untreated WE43, PEO-treated WE43 exhibited excellent cytocompatibility. After incubation for three days, untreated WE43 killed over 90% of lymphocytes while more than 80% of the cells were still vital after incubation with the PEO-treated WE43. PEO-treated WE43 slightly stimulated the activation, proliferation and toxin (perforin and granzyme B) expression of CD8+ T cells. This study demonstrates that the combined assessment of corrosion, cytocompatibility and immunological effects on primary human lymphocytes provide a comprehensive and effective procedure for characterizing Mg variants with tailorable degradation and other features. PEO-treated WE43 is a promising candidate for further development as a degradable biomaterial.

Developments in plasma electrolytic oxidation (PEO) coatings for biodegradable magnesium alloys

Magnesium (Mg) alloys are widely used in bioapplications due to its biodegradable nature, suitable biological and mechanical properties. Also, Mg has a low density (ρ = 1.74 g /cm3) and its elastic modulus (EM = 45 GPa) is much closer to the human bone as compared with other high moduli metallic implants such as Stainless Steels (SS), Cobalt-Chromium (Co-Cr), and Titanium (Ti) based alloys. However, Mg alloys have limited usage in in-vivo applications due to its high degradation rate and corresponding hydrogen gas evolution adjacent to the implant. Therefore, appropriate surface modifications are a must for Mg-based alloys to improve its corrosion resistance, improved bioactivity, and biocompatibility, etc., for biomedical applications. The surface of Mg-based biodegradable materials can be modified by different techniques with its own merits and limitations. Among the various surface modification methods, the plasma electrolytic oxidation (PEO) technique is a relatively new, environmentally friendly, and low-cost process for effective surface modification of Mg-based biodegradable materials with improved bio-functional properties. This paper briefly reviews the developments in plasma electrolytic oxidation (PEO) coatings for magnesium-based biomaterials aiming to control their degradation rate and to improve their bio-functional properties.

Macrophage-derived oncostatin M/bone morphogenetic protein 6 in response to Mg-based materials influences pro-osteogenic activity of human umbilical cord perivascular cells

Macrophages are the central immune cell involved in the foreign body reaction to the implants. Furthermore, the magnesium-based materials could modulate macrophage functions, and subsequently influence bone formation via not clearly understood mechanisms. To analysis the roles of materials (magnesium and its gadolinium-based alloy; Mg and Mg-10Gd) on secretion of macrophages and their effects on pro-osteogenic activity, human mesenchymal stem cells (MSC) and macrophages were cocultured directly on the materials surface. Here, oncostatin M (OSM) - glycoprotein 130 (gp130) signaling complex as well as BMP6/SMAD were found to be involved in the Mg and Mg-10Gd multifactorial modulating osteogenic differentiation. Furthermore, materials upregulated the gene expression of bone morphogenetic protein 6 (BMP6) in macrophages, as well as its protein receptors and mothers against decapentaplegic homolog (SMAD) 1/4/5 in cocultured MSC. Besides, both materials could reduce the secretion of tumour necrosis factor alpha (TNFα) and interleukin 1 beta (IL1β) in macrophages and cocultures. These results collectively imply that Mg and Mg-10Gd could create a beneficial microenvironment for osteogenic differentiation and further support Mg-based biomaterial immunomodulatory properties by modulating the interactions of macrophages and MSC for bone regeneration. Statement of significanceMg-activated macrophages could regulate the pro-osteogenic activity via OSM/gp130 and Smad-related signalling.The neutralisation assay was utilised to confirm the hypothesis of inductive osteoblastic differentiation of human MSC via OSM/gp130 signalling.Current study are essential to evidence that the coordinated communication between macrophages and MSC (OSM/gp130/BMP6/TNFα/IL1β), which could be utilised for improving magnesium-based bone biomaterials and therapeutic applications.

Magnesium in Combinatorial With Valproic Acid Suppressed the Proliferation and Migration of Human Bladder Cancer Cells.

Magnesium, the second most predominant intracellular cation, plays a crucial role in many physiological functions; magnesium-based biomaterials have been widely used in clinical application. In a variety of cancer types, the high intracellular concentration of magnesium contributes to cancer initiation and progression. Therefore, we initiated this study to investigate the likelihood of confounding magnesium with cancer therapy. In this study, the anti-tumor activity of magnesium and underlying mechanisms were assessed in bladder cancer both in vitro and in vivo. The results indicated that the proliferation of bladder cancer cells was inhibited by treatment with a high concentration of MgCl2 or MgSO4. The apoptosis, G0/G1 cell cycle arrest, autophagy, and ER stress were promoted following treatment with MgCl2. However, the migratory ability of MgCl2 treated cells was similar to that of control cells, as revealed by the trans-well assay. Besides, no significant difference was observed in the proportion of CD44 or CD133 positive cells between the control and MgCl2 treated cells. Thus, to improve the therapeutic effect of magnesium, VPA was used to treat cancer cells in combination with MgCl2. As expected, combination treatment with MgCl2 and VPA could markedly reduce proliferation, migration, and in vivo tumorigenicity of UC3 cells. Moreover, the Wnt signaling was down-regulated, and ERK signaling was activated in the cells treated with combination treatment. In conclusion, the accurate utilization of MgCl2 in targeting autophagy might be beneficial in cancer therapy. Although further studies are warranted, the combination treatment of MgCl2 with VPA is an effective strategy to improve the outcome of chemotherapy.

Improving biocompatibility and corrosion resistance of anodized AZ31 Mg alloy by electrospun chitosan/mineralized bone allograft (MBA) nanocoatings

A novel nanofibrous coating containing chitosan and mineralized bone allograft (MBA) nanoparticles was fabricated on AZ31 magnesium alloy via electrospinning in order to enhance corrosion and biocompatibility behavior in a physiological environment. A number of specimens were initially anodized to assess its effect on the improvement of the adhesion between the electrospun nanofibrous coating and the substrate. The coated materials were characterized by using SEM, EDS, FT-IR, and TG. Wettability and the adhesion of the coatings were also studied. In addition, hydrogen evolution and corrosion resistance were evaluated by conducting the immersion test, electrochemical polarization, and EIS tests, respectively. The results showed that both chitosan and chitosan/ MBA composite nanocoating improved the corrosion resistance. Cytotoxicity examination using fibroblast cells indicated that the presence of MBA nanoparticles in chitosan nanofibrous coating has preferable cell adhesion and proliferation. On the whole, application of both chitosan and chitosan/ MBA nanoparticles composite nanofibrous coatings on pre-anodized magnesium appears to be a promising approach in enhancement of the corrosion and biological behavior of magnesium-based biomaterials.

Ag-containing antibacterial self-healing micro-arc oxidation coatings on Mg–Zn–Sr alloys

ABSTRACTThe rapid degradation rate restricts the application of magnesium-based biomaterials. Therefore, we constructed Ag-containing micro-arc oxidation (MAO) coatings on Mg–3Zn–0.5Sr alloys to improve the properties of magnesium alloys. Different concentrations of CH3COOAg (0, 1, 2, 3 g L−1) were added into the electrolyte to investigate the effects of Ag+ content on properties of MAO coatings. The addition of CH3COOAg led to the formation of Ag2O and Ag2CO3 phases, which sealed the micro-pores and improved the corrosion resistance of the samples significantly. The samples with addition of 2 and 3 g L−1 CH3COOAg exhibited strong antibacterial ability against E.coli due to the gradual release of Ag+ in the degradation process. It was verified that the samples with addition of 2 g L−1 CH3COOAg obtained the most high bonding strength, dense construction, excellent corrosion resistance, cytocompatibility and antibacterial properties. The bacteria-killing methods of Ag-containing MAO coatings were discussed in the article.

Optimizing an Osteosarcoma-Fibroblast Coculture Model to Study Antitumoral Activity of Magnesium-Based Biomaterials.

Osteosarcoma is among the most common cancers in young patients and is responsible for one-tenth of all cancer-related deaths in children. Surgery often leads to bone defects in excised tissue, while residual cancer cells may remain. Degradable magnesium alloys get increasing attention as orthopedic implants, and some studies have reported potential antitumor activity. However, most of the studies do not take the complex interaction between malignant cells and their surrounding stroma into account. Here, we applied a coculture model consisting of green fluorescent osteosarcoma cells and red fluorescent fibroblasts on extruded Mg and Mg–6Ag with a tailored degradation rate. In contrast to non-degrading Ti-based material, both Mg-based materials reduced relative tumor cell numbers. Comparing the influence of the material on a sparse and dense coculture, relative cell numbers were found to be statistically different, thus relevant, while magnesium alloy degradations were observed as cell density-independent. We concluded that the sparse coculture model is a suitable mechanistic system to further study the antitumor effects of Mg-based material.