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The cardiovascular diseases (CVD) continue to be the major threat to global public health over the years, while one of the effective methods to treat CVD is stent intervention. Biomedical magnesium (Mg) alloys have great potential applications in cardiovascular stents benefit from their excellent biodegradability and absorbability. However, excessive degradation rate and the delayed surface endothelialization still limit their further application. In this study, we modified a Mg-Zn-Y-Nd alloy (ZE21B) by preparing MgF 2 as the corrosion resistance layer, the dopamine polymer film (PDA) as the bonding layer, and hyaluronic acid (HA) loaded astaxanthin (ASTA) as an important layer to directing the cardiovascular cells fate. The electrochemical test results showed that the MgF 2 /PDA/HA-ASTA coating improved the corrosion resistance of ZE21B. The cytocompatibility experiments also demonstrated that this novel composite coating also selectively promoted endothelial cells proliferation, inhibited hyperproliferation of smooth muscle cells and adhesion of macrophages. Compared with the HA-loaded rapamycin (RAPA) coating, our MgF 2 /PDA/HA-ASTA coating showed better blood compatibility and cytocompatibility, indicating stronger multi-functions for the ZE21B alloy on cardiovascular application. [ABSTRACT FROM AUTHOR]

• A multifunctional coating was constructed on ZE21B alloy for biodegradable vascular stents. • MgF 2 layer and hydrophilic polymers in the functional coating could effectively protect ZE21B alloy from overfast degradation. • Anticoagulant ACH 11 peptides and ECs-selective REDV peptides in the functional coating could dramatically enhance the hemocompatibility and pro-endothelialization capacity of ZE21B alloy. • The functional coating systematically improved the corrosion resistance and biocompatibility of ZE21B alloy in vitro and in vivo. Biodegradable magnesium alloy stents (MAS) have great potential in the treatment of cardiovascular diseases. However, too fast degradation and the poor biocompatibility are still two key problems for the clinical utility of MAS. In the present work, a functional coating composed of hydrophilic polymers and bioactive peptides was constructed on magnesium alloy to improve its corrosion resistance and biocompatibility in vitro and in vivo. Mg-Zn-Y-Nd (ZE21B) alloy modified with the functional coating exhibited moderate surface hydrophilicity and enhanced corrosion resistance. The favourable hemocompatibility of ZE21B alloy with the functional coating was confirmed by the in vitro blood experiments. Moreover, the modified ZE21B alloy could selectively promote the adhesion, proliferation, and migration of endothelial cells (ECs), but suppress these behaviors of smooth muscle cells (SMCs). Furthermore, the modified ZE21B alloy wires could alleviate intimal hyperplasia, enhance corrosion resistance and re-endothelialization in vivo transplantation experiment. These results collectively demonstrated that the functional coating improved the corrosion resistance and biocompatibility of ZE21B alloy. This functional coating provides new insight into the design and development of novel biodegradable stents for biomedical engineering. [ABSTRACT FROM AUTHOR]

Magnesium (Mg) alloys are promising materials for cardiovascular stent applications due to their good biocompatibility and biodegradability. However, in vitro and in vivo corrosion tests reveal that Mg alloy stents suffer from a rapid corrosion rate and severe localized corrosion, which is limiting their widespread application. To solve the problem of uneven degradation of stents, a HTHE (long-time and high-temperature heat treatment, large-reduction-ratio hot extrusion) process is used to manufacture Mg-Zn-Y-Nd alloy microtubes in this study. The heat treatment is to dissolve alloying elements and reduce the size of SPPs, and the hot extrusion is to acquire fine-grained and strongly textured microtubes. The microstructural characterization shows that coarse second phases in as-cast alloy are refined and uniformly distributed in matrix of microtubes. After hot extrusion, microtubes show strong texture with basal plain oriented parallel to the longitudinal section (LS). The corrosion testing indicates that severe localized corrosion occurs on the cross section (CS) while localized corrosion is alleviated on the LS. Based on the different corrosion properties of the LS and CS, HTHEed microtubes are promising for solving the problems of rapid corrosion rate and severe localized corrosion of Mg alloy stents. [ABSTRACT FROM AUTHOR]

Magnesium alloys have narrow available slip result from close-packed hexagonal structure that limit their processing properties. In the recent work, the Mg-2Zn-0.46Y-0.5Nd, as materials for degradable stents, was applied to produce as-extruded micro-tube with an outer diameter of 3.0 mm and a wall thickness of 0.35 mm by hot extrusion with an extrusion ratio of 105:1 at 653 K and rapid cooling. The fine microstructure of the dynamic recrystallization of as-extruded micro-tube could be preserved by rapid cooling such as water-cooled, resulting in more excellent mechanical properties relative to air-cooled micro-tube. The addition of rare earth elements Y and Nd results in continuous dynamic recrystallization dominated the dynamic recrystallization mechanism. During the hot extrusion process, the activation of the non-basal slip system, especially the pyramidal 〈 c + a 〉 slip, could significantly weaken the texture strength, and the as-extruded micro-tube exhibits weak "RE" texture components 〈 01 1 ¯ 1 〉 ∥ ED and 〈 1 ¯ 2 1 ¯ 1 〉 ∥ ED. Hence, the magnesium alloy micro-tube prepared by the rapid cooling has fine microstructure and weak texture, which is favorable for further process and governance. [ABSTRACT FROM AUTHOR]

Magnesium alloys were considered to be used as biodegradable implants due to their biocompatibility, biodegradability and nontoxicity. However, under the simultaneous action of corrosive environment and mechanical loading in human body, magnesium alloys are easy to be affected by corrosion fatigue and stress corrosion cracking. In this work, the fatigue behavior of the extruded Mg–Zn–Y–Nd alloy used for vascular stents was studied both in air and in simulated body fluid (SBF). It was revealed that the fatigue limit of as-extruded Mg–Zn–Y–Nd alloy in air is about 65 MPa at 107 cycles, while there is no limit in SBF and shows a linear relationship between the fatigue life and stress amplitudes. The fatigue crack source in air was formed by the inclusions and defects. However, the stress corrosion and hydrogen embrittlement are the main reasons for the formation of the fatigue initial crack source in SBF. [ABSTRACT FROM AUTHOR]

Abstract: Magnesium alloys are promising candidate materials for cardiovascular stents due to their good biocompatibility and degradation properties in the human body. However, in vivo tests also show that improvement in their mechanical properties and corrosion resistance is necessary before wide application. In this study, cyclic extrusion compression (CEC) was used to enhance the mechanical properties and corrosion resistance of Mg–Zn–Y–Nd alloy. The results show that the grain size was greatly refined to 1 m after CEC treatment. The second phase distributed along the grain boundaries with grid shape and nano-sized particles uniformly distributed in grains. The elongation (), ultimate tensile strength (UTS) and yield strength (YS) of the CEC treatment samples were 30.2%, 303 MPa and 185 MPa respectively. The CEC treated samples showed homogeneous corrosion because of the grain refinement and the homogeneous distribution of nano-sized second phase. The corrosion current density of the alloy decreased from 2.810 A/cm to 6.610 A/cm after CEC treatment. Therefore, improved mechanical properties, uniform corrosion and reduced corrosion rate could be achieved by CEC. [Copyright &y& Elsevier]

The localized corrosion caused by the interphase potential differences and incompleteness of the corrosion product layer results in the premature failure of Mg alloys. In biomedical applications, understanding about the corrosion behavior of Mg alloys in complex environment is still insufficient. In this work, mechanical tests after corrosion were employed to indirectly but generally reflect the localized corrosion of Mg alloy in the protein-containing electrolytes. The results reveal that protein alters the Mg corrosion mode to uniform corrosion and an appropriate amount of protein is beneficial for maintaining its mechanical bearing capacity. This work is helpful for understanding the corrosion behavior of Mg alloys and consummating degradation evaluation systems for Mg alloys. [Display omitted] • Mechanical tests after corrosion is employed to indirectly but generally reflect the localized corrosion of Mg alloy. • The complexation of BSA and Mg2+/Ca2+ leads to the uniform corrosion of Mg alloy. • BSA increases the corrosion rate of Mg alloy but the decline of mechanical properties is less. • Corrosion tests in simple media probably do not accurately reflect the actual service performance of Mg alloy. [ABSTRACT FROM AUTHOR]

Highlights: [•] Microstructure evolution of Ca-def HA coating was systematically investigated. [•] Poor crystalline Ca-def HA has been formed at the deposition time of 5min. [•] Reasons for direct formation of Ca-def HA coating on Mg–Zn–Ca alloy are discussed. [ABSTRACT FROM AUTHOR]

Highlights: [•] It’s effective to fabricate a bio-composite coating on Mg alloy by this method. [•] Most HA got involved in the coating and turned into TCP during the MAO process. [•] HA and the sintering-caused phases changed the cross-section into dense structure. [•] The bioactivity and corrosion resistance of the coating were improved. [ABSTRACT FROM AUTHOR]

[Display omitted] • A ceria/calcium-phosphate functional composite coating was constructed on magnesium alloy by two-step electrodeposition. • The construction approach endows multi-functions of the coating. • Formation mechanism of the coating was proposed. • Corrosion behavior, hemocompatibility, cytocompatibility, and antibacterial property of the coating were investigated. Magnesium (Mg) and its alloys have been regarded as potential orthopedic implant materials due to their suitable properties but face challenges due to rapid biocorrosion and insufficient bio-functionality, necessitating surface treatment to mitigate dysfunction. In this work, a two-step electrodeposition was employed to construct a ceria/calcium-phosphate (Ce/Ca-P) composite coating on Mg alloys. This construction approach endows multi-functions of the coating. The ceria interlayer ameliorates adhesion strength. The pin-like structure on the outer layer of the Ce/Ca-P coating enhances the antibacterial capabilities of the coating in the early stages of the implantation. The calcium-phosphate outer layer and the ceria interlayer induce the deposition of calcium and phosphate ions promoting bone healing in the mid-term. The introduction of the ceria interlayer significantly reduces the corrosion rate of the Mg alloy by 86.7% improving the corrosion resistance of the alloy, which is of great significance to maintain the service reliability of the device during the long-term service period. The results indicate that the Ce/Ca-P coating exhibits good hemocompatibility and cytocompatibility. This type of developed coating with anti-corrosive and bio-functionalized capability helpfully advances the application of Mg-based bone implants. [ABSTRACT FROM AUTHOR]

To build a suitable corrosion environment for testing the degradation behavior of magnesium alloy in vitro, the medium and test environment are constantly optimized. However, the applicability of medium renewal mode is still vague. In this study, based on three representative test protocols, the influence of the specific ratio of media volume to surface area and the disposable medium real-time renewal mode (flow-through) on Mg corrosion were investigated. It is found that in flow-through medium renewal mode, the composition of the medium is maintained quasi-constant which is essential for corrosion tests. The selection suggestion on medium renewal mode was also proposed. This work is beneficial for ultimately establishing the representative in vitro testing protocols for Mg bioabsorbable materials. • The ratio of medium volume to surface area affects Mg corrosion. • The disposable medium real-time renewal mode maintains the medium stability. • Different media and materials have distinct sensitivity to medium renewal modes. • Medium renewal modes of corrosion test should be prudently selected based on actual needs. [ABSTRACT FROM AUTHOR]

In this study, conductive silk fibroin (SF) and poly (3, 4-vinyldioxythiophene): poly (styrene sulfonate) (PEDOT: PSS) coating (SF-PEDOT: PSS) was successfully prepared on the ZE21C magnesium alloy via the chemical grafting process so as to improve corrosion resistance and achieve osteoimmunity. The microstructure, composition, surface wettability and corrosion behaviors of the coatings were investigated by SEM, EDS, FTIR, XPS, water contact angle and potentiodynamic polarization test. Results revealed that the chemical grafting of SF-PEDOT: PSS coating occurred, wherein, SF reacted with polydopamine to form –CO–NH- bond, and PEDOT: PSS reacted with polydopamine to form NH 3 + bond. In addition, one order of magnitude reduction of corrosion density (i corr) as well as the positively shifted corrosion potential (E corr) by 107 mV as compared with that of the substrate was observed. Cytocompatibility results demonstrated that this coating could highly facilitate the adhesion, spreading, and proliferation of bone healing related cells (MC3T3-E1 and RAW264.7 cells). Moreover, it promoted the release of M2 phenotype factors (IL-4, IL-10 and TGF- β 1), but inhibited the release of M1 phenotype factors (IL-6 and TNF- α), achieving the regulation of macrophage phenotype transformation. Furthermore, higher release of ALP, COL I and OCN revealed the acceleration of bone mineralization. In summary, the obtained SF-PEDOT: PSS coatings possessed the remarkably improvement of anticorrosion ability and good bioactivity which can serve as a promising strategy for surface design of magnesium alloys in the orthopedic applications. • A conductive SF-PEDOT: PSS coating was first prepared on magnesium-based alloys. • SF and PEDOT:PSS was conguated via PDA forming –CO–NH- and NH 3 + bond, respectively. • It can effectively retard corrosion with positively shifted E corr and lower i corr. • Good cytocompatibility was achieved with MC3T3-E1 cells and macrophages in vitro. • Regulation of macrophage transformation with osteogenic ability was found in vitro. [ABSTRACT FROM AUTHOR]

A controllable corrosion rate is an ideal condition for magnesium (Mg) alloy as biodegradable metallic materials. Calcium carbonate (CaCO 3) coating has been proven to possess a robust anti-corrosion property for Mg alloy. To further regulate the morphology and corrosion protection ability of the CaCO 3 coating, in current study, different organic molecules, including amino acids (Tyr and Glu), amine (DOPA), proteins (COL and BSA) and peptide (CPP), were added into the coating formation electrolyte, affecting the morphology, polymorph composition, and the crystal size distribution of precipitated CaCO 3. The results revealed that Tyr exhibited little effect on the polymorph composition of the CaCO 3 -based coating, while Glu, DOPA, COL and BSA generally promoted the formation of vaterite but inhibited the formation of rod-like aragonite precipitates and calcite in the coatings. In contrast, CPP suppressed the precipitation of CaCO 3 crystals because of its high affinity to Ca2+ ions. The addition of those organics reduced the size of calcite crystals. Consequently, the organic molecules mediated CaCO 3 -based coatings showed better compactness and homogeneity, which maintained the strong adhesion strength of the coatings to the substrate and further enhanced the corrosion protection abilities of the coating for the substrate. The results of the study pave the way for the development of CaCO 3 -based coatings with advanced properties for Mg alloys as biomedical materials. • The regulation effects of several organic molecules on the morphologies and properties of CaCO 3 -based coatings were investigated. • Tyr shows little influence on the polymorph composition of the CaCO 3 coating. • Glu, DOPA, COL, and BAS stabilize vaterite and inhibit the rod-like aragonite precipitation. • CPP inhibits the crystallization of CaCO 3 due to its high affinity to Ca2+ ions. • The addition of organic molecules further enhances the anticorrosion properties of the CaCO 3 -based coatings. [ABSTRACT FROM AUTHOR]

Research about magnesium corrosion inhibitors focuses on their influence on corrosion rate, but little attention is paid to whether the service reliability of alloys is improved by the inhibitors. In this work, the effects of selected corrosion inhibitors on the corrosion rate and localized corrosion behavior of magnesium alloy were compared. It is found that some corrosion inhibitors fail to inhibit the localized corrosion of magnesium, resulting in the inability to effectively maintain the mechanical bearing capacity of the corroded magnesium alloy. This study is of great significance for establishing reasonable screening and evaluation criteria for magnesium alloy corrosion inhibitors. • SDBS and PDCA effectively slows down the corrosion rate of Mg alloy but cannot completely inhibit localized corrosion. • SA slightly accelerates Mg corrosion but delays the decline of mechanical properties of alloy. • PCCys significantly slows down the corrosion rate and inhibit the localized corrosion of Mg alloy. • Inhibition efficiency of corrosion inhibitor has no direct link to its effect on the mechanical bearing capacity of Mg alloy. [ABSTRACT FROM AUTHOR]

• Yttrium-oxygen layer is found under dynamic flow. • Yttrium-oxygen layers decreases the corrosion rate of microtubes under dynamic flow. • A suitable selection of rare earth elements could further improve the corrosion resistance. In the corrosion tests, yttrium (Y) element reacts with oxygen (O) element to form Y-O compound, generating a protective corrosion layer to isolate magnesium (Mg) alloy from further attack of corrosion medium. To better illustrate the protective effects of Y-O compound on corrosion morphology of biodegradable Mg alloys stents, in vitro dynamic corrosion tests were conducted for ZE21B Mg alloy microtubes. Under dynamic flow, Mg-O layer and calcium-phosphate (Ca-P) layer peeled off from microtubes, and the compact and flat Y-O layer started to emerge, protecting ZE21B Mg alloy microtubes against flow induced corrosion. [ABSTRACT FROM AUTHOR]

Abstract: Besides common immersion tests, it''s essential to investigate biocorrosion of degradable magnesium alloys in physiological environment under stress that bone implants bear in vivo. Using self-designed immersion method simulating in vivo conditions and conventional immersion test, corrosion morphologies and pH variations of the coated samples with or without compressive stress and the substrate alloy were studied. Results showed that the applied stress can change the degradation mode of coated samples and promote corrosion process, causing peeling-off locations on the coating and continuous increase of pH value. Meanwhile, biocompatibility of the coated samples was not apparently affected by the compressive stress. [Copyright &y& Elsevier]

• Electropolymerized dopamine (ePDA) coating was prepared on Mg-Zn-Y-Nd alloy surface. • ePDA coating surface is uniform and doped with salicylate and magnesium. • ePDA coating induced more uniform surface of Poly (l -lactic acid) (PLLA) coating than dip polydopamine (dPDA) coating. • ePDA/PLLA coating showed excellent adhesion and higher corrosion resistance than dPDA/PLLA coating. The high surface roughness of dip polydopamine (dPDA) coating on magnesium alloy could decrease the quality of secondary modification. In the present study, we report an electropolymerized dopamine (ePDA) coating on Mg-Zn-Y-Nd alloy from sodium salicylate aqueous solutions by galvanostat method to address this problem. The coating formation process and coating structure were investigated. Then, a Poly (l -lactic acid) (PLLA) coating was prepared on ePDA and dPDA treated samples. The SEM results reveal that the ePDA film appeared to be more uniform than dPDA coating and was doped with salicylate and magnesium ions. ASTM D3359 -09 "Tape test" shows excellent adhesion of the ePDA/PLLA layer. The electrochemical impedance spectroscopy and polarization curves demonstrate ePDA/PLLA film has a better corrosion resistance than dPDA/PLLA film, owing to the structural difference of polydopamine anchoring layer. [ABSTRACT FROM AUTHOR]

[Display omitted] • The relation between the features and mechanical behavior of Mg alloys was modeled. • The stacking ensemble model can perform better than single models. • The mechanical properties of biomedical Mg alloys are accurately predicted. In this work, a dataset was constructed by collecting the data of mechanical properties for 365 magnesium (Mg) alloys. Using the composition and process parameters of Mg alloys as input variables, six machine learning (ML) models including ridge regression, support vector machine regression, gradient boosting regression tree, random forest, CatBoost, and Gaussian process regression, were built to predict the ultimate tensile strength (UTS), yield strength (YS), and elongation (EL) of Mg alloys. These single models were then integrated by using model ensemble in order to further improve the prediction accuracy. The results showed that the ensemble model achieved a higher prediction accuracy and better generalization ability for UTS, YS, and EL than that for the single models. The mechanical properties predicted by the optimal model were very close to the experimental values, demonstrating that ML is an effective method for predicting the mechanical properties of biomedical Mg alloys. [ABSTRACT FROM AUTHOR]

Magnesium alloys are considered to be one of the most promising stent materials due to their good biological compatibility and biodegradable properties. However, the poor workability at room temperature restricts the processing of high-precision micro-tubes for the application as stent materials. In this study, Mg–Zn–Y–Nd alloy tube blank was firstly produced through hot extrusion. By multi-pass cold drawing combining with interpass annealing, the extruded tube blank can be processed into high-precision micro-tube with an outer diameter of about 2.0 mm and a wall thickness of about 0.15 mm. The drawn micro-tube after annealing exhibits improved mechanical properties with an ultimate tensile strength of about 298 MPa and a large breaking elongation of up to 20%. Meanwhile, the micro-tube shows good corrosion resistance with a trend of uniform corrosion in simulated body fluid solution. The investigation revealed that a significant improvement in the mechanical properties is mainly attributed to grain refinement and texture weaken, while the good biodegradable properties is related with the low density of crystallographic defects as well as fine and homogeneous microstructure. As a result, the successful processing of magnesium alloy micro-tube provides the precursor for laser engraving stents. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel CaCO 3 hybrid coatings are firstly evaluated in vitro and in vivo on orthopedic Mg alloys. • Glu significantly optimizes the composition and morphology of CaCO 3 coating. • CaCO 3 -based coatings largely inhibit the in vitro and in vivo degradation of Mg alloy. • CaCO 3 @Glu hybrid coating exhibits accelerated osteogenesis in vitro and in vivo. Fast degradation of Mg alloys and slow bone regeneration process largely impede their clinical applications as one kind of degradable metallic orthopedic implants. In current study, novel calcium carbonate (CaCO 3) coatings are prepared via the hydrothermal method and optimized via the addition of glutamate acid (Glu) or dopamine (DOPA) to improve the degradation and biological performance of the MgZnCa alloy. The results revealed that the CaCO 3 coating was mainly composed of rhombohedral calcite aggregates and deposited rod-like aragonite. Whereas, the introduction of Glu or DOPA stabilized plate-like vaterite via the adsorption or incorporation of organic molecules, and suppressed the deposition of rod-like aragonite on CaCO 3 hybrid coating with lower roughness, higher adhesion strength and thickness. Thus, CaCO 3 hybrid coatings endowed the MgZnCa alloy with more favorable in vitro degradation resistance. Furthermore, all CaCO 3 -based coatings showed good in vitro cytocompatibility, while CaCO 3 @Glu hybrid coating exhibited the best in vitro osteogenic activity of osteoblasts, attesting the synergistic effect of Glu and vaterite on the biological activity of the MgZnCa alloy. In vivo results verified the significantly inhibited degradation and promoted osteogenesis of the CaCO 3 @Glu hybrid coating. These results provide important guidelines and rationality for the further application of the CaCO 3 -based coatings on orthopedic implants towards more excellent clinical performance. [ABSTRACT FROM AUTHOR]

The development of multifunctional Mg-based active implants with controllable degradation and antibacterial capabilities has become a hotspot in the research field of biodegradable metallic materials. To this end, a BN nanosheets (BNNS) _ vancomycin (Van) @ chitosan (CS) nanocomposite coating containing two antibacterial components (BNNS and Van) was prepared on Mg alloys via a micro-arc oxidation (MAO) pre-treatment combined with following electrodeposition. The related characterizations of the coating show that the composite coating has a high roughness, hydrophobicity and fair corrosion resistance. In vitro antibacterial experiments show that the BNNS_Van@CS/MAO composite coating have obvious inhibitory effect on the growth of both E. coli and S. aureus. The antibacterial effect of the BNNS_Van@CS/MAO composite coating was attributed to the synergistic effect of CS, BNNS and Van. This study provides a valuable surface modification strategy for developing multifunctional Mg-based implants with good corrosion resistance and antibacterial properties. [Display omitted] • BNNS@CS-loaded vancomycin composite coatings were prepared on ZE21C alloy. • BNNS_Van@CS/MAO coating provides an effective protection for the ZE21C alloy. • BNNS_Van@CS/MAO coating has good antibacterial effect against E.coli and S.aureus. • BNNS@CS coating and vancomycin have synergistic antibacterial effects. [ABSTRACT FROM AUTHOR]

[Display omitted] • Corrosion of the substrate was effectively inhibited by the presence of MgSO 4 during coating preparation. • MgSO 4 results in the transformation of the middle calcite from cubic to spindle-shaped crystals. • Mg2+ and SO 4 2− promote the precipitation of metastable aragonite and vaterite in the outer layer. • The corrosion resistance of CaCO 3 coating for Mg substrate can be adjusted by MgSO 4 concentration. • CaCO 3 could be transformed into Ca-P products during immersion. Too fast corrosion of magnesium(Mg)-based materials is one of main concerns prior to their applications as biodegradable biomaterials. In present study, a CaCO 3 coating on Mg alloy is developed via hydrothermal method to control the corrosion of Mg2Zn0.2Ca alloy. The morphology and anti-corrosion property of the CaCO 3 protective coating are adjusted by the concentration of MgSO 4 in coating preparation electrolyte. The results reveal that the presence of MgSO 4 stabilizes the precipitation of metastable CaCO 3 crystalline (aragonite and vaterite) and affects the structure and growth rate of the middle calcite layer on Mg alloy surface, which leads to the transformation of cubic calcite into small rhombohedral aggregates in the middle layer as the concentration of MgSO 4 increases. Consequently, the corrosion protection property of the coating is significantly enhanced due to the increased compactness of the coating as the concentration of MgSO 4 increases from 0 mM to 20 mM. Whereas, with further increase of MgSO 4 concentration, the spindle-shaped calcite crystalline formed in the middle layer provides more penetrable boundaries, leading to a lower resistance for Mg substrate. Long-term immersion tests indicate the transformation of CaCO 3 into calcium phosphate, which exhibits a great prospect for Mg alloys as orthopedic implants. [ABSTRACT FROM AUTHOR]

To reduce the degradation of magnesium alloy, improve its antibacterial activity, and fulfil specific requirements for bone implant material applications, a chitosan (CS)/boron nitride nanosheet (BNNS) composite coating was constructed on the surface of Mg–Zn–Y–Nd–Zr alloy via electrodeposition. The results show that BNNS was uniformly embedded and significantly changed the morphology and roughness of the CS coating. Electrochemical and immersion tests suggest that the CS–BNNS composite coating can effectively provide a long-term protection to the substrate. The antibacterial activity results show that BNNS significantly improved the antibacterial activity of the CS coating against E. coli and S. aureus , and verified the sterilisation mechanism of BNNS in contact with bacterial membranes. Meanwhile, cytocompatibility tests showed that the CS–BNNS coating has no adverse effect on the adhesion and proliferation of mouse osteoblasts cells. Thus, the fabricated CS–BNNS composite coating could be a promising application in surface modification for Mg-based bone implants. In this study, a chitosan (CS)/boron nitride nanosheet (BNNS) composite coating was constructed on a magnesium (Mg) alloy via electrodeposition. The CS–BNNS coating improves the antibacterial activity and reduces the degradation rate of the Mg alloy. BNNS was uniformly embedded into the chitosan coating, which significantly improved the bactericidal activity of the CS coating. Meanwhile, cytocompatibility tests showed that the CS–BNNS coating has no adverse effect on the adhesion and proliferation of mouse osteoblasts cells. [Display omitted] • CS–BNNS coatings were synthesised on a Mg alloy via electrodeposition. • CS-BNNS coating reduces the degradation rate of Mg alloy. • CS-BNNS coating improves the antibacterial activity of Mg alloy. [ABSTRACT FROM AUTHOR]

Highlights: [•] The OH-terminated MAO surface promoted the generation of TiO2 layer. [•] The interface was bonded by the interaction of phosphate radical and Ti–O bond. [•] The chemically anchored interface contributed to the in vitro degradation slowdown. [ABSTRACT FROM AUTHOR]

Abstract: A Mg phosphate coating was prepared on home-developed Mg–Zn–Ca alloy to improve its anticorrosion performance in simulated body fluid (SBF, Kokubo solution). The coating was prepared by micro-arc oxidation (MAO) method at the working voltage of 120–140V. Evident improvement of anticorrosion was obtained even through the surface was porous. To further diminish the contact with SBF, a TiO2 layer was coated on the porous MAO layer by sol–gel dip coating followed by an annealing treatment. The coatings were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS). The electrochemical performance of the MAO and TiO2/MAO coated alloys was evaluated by anodic polarization measurements. The pores on Mg phosphate layer provided accommodation sites for the subsequent TiO2 sol–gel coating which sealed the pores and hence significantly enhanced the anticorrosion while single MAO coating only improve anticorrosion within a limited range. The present result indicates that fabrication of composite coatings is a significant strategy to improve the corrosion resistance of Mg–Zn–Ca alloy and other alloys, thus enhancing the potential of using Mg alloys as bio-implants. [Copyright &y& Elsevier]

Abstract: The microstructures, mechanical and corrosion properties of three extruded Mg–2Zn–0.46Y–xNd alloys (x =0.0, 0.5, 1.0wt%) were studied by optical microscopy, scanning electronic microscopy (SEM), electrochemical measurements and tensile tests. Microstructural observations indicated that Nd led to the uniformity and the variation of morphology of major second phase; tensile tests showed that Nd can improve the ductility at moderate amount (0.5wt%) and will be detrimental up to 1.0%; Mg–2Zn–0.46Y–0.5Nd alloy exhibited excellent mechanical properties (σ b , 269.0MPa, σ 0.2, 165.6MPa and elongation, 24%); electrochemical tests revealed that Nd can enhance the corrosion resistance and Mg–2Zn–0.46Y–1.0Nd alloy had lowest corrosion current density, which was reasoned that the line-shape and rodlike NdZn2 phase might serve as corrosion barriers and the dissolved Nd can raise the electrode potential of the matrix. [Copyright &y& Elsevier]

Abstract: In present paper, an in vivo study was carried out on uncoated and calcium-deficient hydroxyapatite (Ca-def HA) coated Mg–Zn–Ca alloy to investigate the effect of Ca-def HA coating on the degradation behavior and bone response of magnesium substrate. Magnesium alloy rods were implanted into rabbit femora and evaluated during 24 weeks implantation. The characterization of both implants indicates that in vivo degradation of the Ca-def HA coating and magnesium substrate occurs almost simultaneously, and in vivo valid life of the coating is about 8 weeks, after that the degradation rate of the coated implants increases obviously. The main reasons for the Ca-def HA coating degradation can be attributed to its reaction with body fluid and the substitution of Mg2+ ions in Ca-def HA. Histopathological examinations show that the Ca-def HA coating has good osteoconductivity and is in favor of the formation of more new bone on the surface of magnesium alloy. So the Ca-def HA coating could not only slow down in vivo degradation of magnesium alloy but also improve its bone response. [Copyright &y& Elsevier]

Abstract: A nano TiO2 film was coated on AZ31 alloy substrate by sol–gel method. The TiO2 film was characterized by X-ray diffractometry (XRD), differential scanning calorimetry-thermogravimetric analysis (DSC-TG), field emission scanning electron microscopy (FE-SEM) and energy dispersion spectroscopy (EDS). The degradation of the nano-TiO2 coated alloy was evaluated by immersion test and electrochemical measurement. An attempt was made to relate corrosion of coated alloys with the annealing treatment and resultant structural evolution. [Copyright &y& Elsevier]

Abstract: Magnesium alloys have been widely investigated in the field of biomaterials due to their moderate mechanical properties close to human bone and gradual degradation in human physiological environment without second surgeries. But results from clinical studies showed that magnesium implants suffered from too rapid degradation in human physiological environment. To reduce the degradation rate of magnesium alloys, surface modification is essential and effective besides element alloying. In this study, TiO2 films were deposited on Mg–Zn alloy by direct current reactive magnetron sputtering. The morphology and structure of the films were characterized by atomic force microscopy (AFM), scanning electron microscope (SEM) and X-ray diffraction (XRD). The corrosion resistance in simulated body fluid (SBF) at 37°C was evaluated by potentiodynamic polarization and hydrogen evolution tests. The corrosion behavior of the samples was investigated by SEM with energy dispersive spectroscopy (EDS) after immersion for different periods. The results showed that the compact films were composed of particles with the size of about 100nm and could effectively improve the corrosion resistance in SBF. After immersion for 10 days, the corrosion rates of the substrates and samples with TiO2 films were 4.13mm/y and 1.95mm/y, respectively. During the immersion, the TiO2 films could induce the growth of hydroxyapatite (HAp) to improve the bioactivity of the samples. [ABSTRACT FROM AUTHOR]

• The PGA coating has been prepared on magnesium alloy by electrografting. • Covalent bonding exists between the coating and magnesium substrate. • The synthesis mechanism of PGA coating was explained. Polyglycolide (PGA), owing to its optimal biocompatibility and degradability, is widely used in the biomedical application. In this work, a catalyst-free approach at room temperature for preparing PGA coating on magnesium alloy with controllable morphology and thickness is proposed. The morphology and thickness of the PGA coating is controlled by adjusting the electrografting duration. ToF-SIMS analysis showed that the electrografting provides a covalent bond connection between the PGA coating and the magnesium alloy substrate. In addition, the formation mechanism of PGA coating is explained by the experimental results. This work verifies the applicability of electrografting to prepare polymeric coating under specific conditions. [ABSTRACT FROM AUTHOR]