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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]

Hard nitride coatings have the prospect of acting as protective layers for cutting tools because of their excellent mechanical properties and wear resistance. To enhance the mechanical, tribological, and high-temperature oxidation properties, the structural design of the coating is important. In this study, TiSiN, CrAlN/TiSiN bilayer and CrAlN/TiSiN multilayer coatings were deposited on the surface of high-speed steel by multi-arc ion plating technology. The microstructure, phase composition, mechanical properties and high-temperature tribological properties of prepared coatings were analyzed. Results indicated that the TiSiN and CrAlN/TiSiN bilayer coatings contain TiN phases and the CrAlN/TiSiN multilayer coating contains three main phases of TiN, AlN and CrN. The CrAlN/TiSiN multilayer coating possesses a denser microstructure than the other two coatings. The multilayer structure improves the cohesive and bonding strength of the coating by reducing the shear stress. The CrAlN/TiSiN multilayer coating exhibits a stable coefficient of friction and excellent wear resistance during high-temperature friction. The formation of TiO2 and Al2O3 oxide layers on the surface of the coating in a high-temperature environment contributes to the desired tribological properties of the coatings. [ABSTRACT FROM AUTHOR]

Tool coatings exhibit different tribological behavior when cutting dissimilar materials, and understanding the differences is crucial for their service life. In this study, CrAlN/TiSiN multilayer coating was deposited by the arc ion plating technique, and its microstructure, load-bearing capacity, and toughness were investigated as well as the tribological behavior of the coating sliding against 7A09 Al alloy and GCr15 bearing steel at different temperatures. The results indicated a high fluctuation in the friction coefficient between the coating and 7A09 Al alloy above 150 °C, and the coating exhibited a negative wear rate. The friction coefficient between the coating and GCr15 bearing steel shows a decreasing trend above 150 °C, and the wear surface of the coating showed a smooth morphology. [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]

• 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] • 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]

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]

Severe and non-uniform degradation of magnesium (Mg) alloys limits their general application in the field of vascular stents. Polymer coatings, which have been widely used in biodegradable materials, can simultaneously reduce degradation and improve the biocompatibility of Mg alloys. In this study, polycaprolactone (PCL) coating was prepared on Mg–Zn–Y–Nd alloy by electrografting. The microstructure of the prepared coating is significantly influenced by current density and monomer concentration, according to scanning electron microscope/energy dispersive spectroscopy results. The electrografted PCL coating has two molecular weights, 15.5 × 103 g·mol−1 and 1.08 × 103 g·mol−1, according to gel permeation chromatography results. Electrochemical and immersion tests show that the electrografted PCL coating has better anti-corrosion properties than the PCL coating prepared using the traditional dipping method. Meanwhile, human umbilical vein endothelial cells and smooth muscle cells culture results show that electrografted PCL coating improves the magnesium alloy's ability to maintain cell viability. Furthermore, arginine-glycine-aspartic acid was fixed on the surface of the PCL coating to confirm the possibility of functionalisation of the electrografted PCL coating. The results show that the composite coating promotes cell adhesion. In this study, polycaprolactone (PCL) coating was prepared by the ring-opening polymerization of ε-caprolactone by electrografting. The micro-morphology of PCL coating changed from cauliflower-like porous structure to smooth surface after heat treatment. The cytocompatibility of the PCL coating is further improved by loading arginine-glycine-aspartic acid, which is expected to be used as a multi-functional coating for cardiovascular stents. [Display omitted] [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]