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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]

In this study, multiple addition of rare earth (RE) and manganese (Mn) to AZ61 was conducted aiming to find out the influence to corrosion resistance. AZ61 containing different amounts of RE and Mn was investigated by electrochemical measurement in condition of 3.5 wt% NaCl solution at 25 °C. Gravimetric measurement was conducted in 5 wt% salt spray at 35 °C and 3.5 wt% NaCl solution at 25 °C. Samples were characterized by SEM, EDS, OM and XRD. The result shows that with RE addition Al8Mn5 in AZ61 changed into Al10RE2Mn7. The quantity of β phase is reduced significantly. The multiple addition of RE and Mn improved the corrosion resistance of AZ61. When the ratio of Mn and RE is 0.3, alloy has the best property of corrosion resistance. In addition, the composite addition removed the impurity elements in AZ61 especially Fe. [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]

• 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]

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]

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: 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]

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]