Magnesium Alloy Stents Research Articles

Neuroprotective effects of intraperitoneally injected Mg alloy extracts on middle cerebral artery occluded mouse with reperfusion injury

Magnesium (Mg) alloy stents have been commercialized for the treatment of cardiovascular diseases and extensively studied for possible implantation in major organs. However, the in vivo studies regarding the neuroactivity of Mg alloys extracts are few. Therefore, the safety and neuroprotective effects of released degradation products (Mg2+ and H2) from Mg alloys on ischemic brain tissues were investigated. To be specific, C57BL/6 mice with middle cerebral artery occlusion (MCAO) were injected intraperitoneally of saline, pure Mg extracts, WE43 extracts and hydrogen (H2)-removed WE43 Mg alloy extracts (75 mL/kg) respectively immediately after reperfusion. The neurobehavioral assessment stated clearly that WE43 extracts could remarkably recover the neurological deficits of MCAO mice. We explored the underlying mechanisms and demonstrated that the Mg2+ and H2 from WE43 extracts could perform anti-inflammatory and anti-oxidative function after MCAO in mice, by increasing the expressions of IL-4, TGF-β1, SOD1 and decreasing the expressions of IL-1β, CXCR2, MDA. Simultaneously, Mg2+ and H2 contributed to increase cerebral blood flow and restore blood-brain barrier integrity. In conclusion, this study provides certain theoretical representation of the application of Mg alloy stents in intracranial vessels.

Degrees of Inflammation in the Treatment of Subglottic Stenosis in a Rabbit Model: Histopathological Assessment of a Novel Bioabsorbable Ultra-high Ductility Magnesium Alloy Stent

ObjectiveUtilizing a novel histopathological scoring system and subglottic stenosis (SGS) rabbit model, we aimed to compare degrees of inflammation and severity of narrowing in the subglottis between two minimally invasive therapeutic modalities: endoscopic balloon dilation (EBD) alone versus EBD with placement of a bioabsorbable ultra-high ductility magnesium (UHD-Mg) alloy stent. MethodsSGS was induced endoscopically via microsuspension laryngoscopy in 23 New Zealand white rabbits. The control group (n = 11) underwent EBD alone, the study arm (n = 12) underwent EBD with implantation of bioabsorbable UHD-Mg alloy stents. Rabbits were euthanized at 2-, 3-, and 6-weeks after SGS induction, coinciding with wound healing stages. Using Optical Coherence Tomography (OCT), cross-sectional areas of airways were compared to calculate the mean percentage of intraluminal area at sequential time points. A novel histopathological scoring system was used to analyze frozen sections of laryngotracheal complexes. The degree of inflammation was quantified by scoring changes in inflammatory cell infiltration, epithelial ulceration/metaplasia, subepithelial edema/fibrosis, and capillary number/dilation. Univariate analysis was utilized to analyze these markers. ResultsWe found rabbits implanted with the bioabsorbable UHD-Mg alloy stent had statistically significantly higher scores in categories of hyperplastic change (stents vs controls: 1.48 vs 0.46 p < 0.001), squamous metaplasia (22 vs 5 p < 0.001), and neutrophils/fibrin in lumen (31 vs 8, p < 0.001). Rabbits who received EBD alone had higher scores of subepithelial edema and fibrosis (2.70 vs 3.49, p < 0.0256). The stented rabbits demonstrated significantly increased mean percent stenosis by intraluminal mean area compared to controls at 2 weeks (88.56 vs 58.98, p = 0.032), however at all other time points there was no significant difference between intraluminal subglottic stenosis by mean percent stenosis area. DiscussionRabbits with SGS treated with UHD-Mg alloy stents demonstrated histopathologic findings suggestive of lower levels of tracheal fibrosis. This could indicate a reduced tendency towards the development of stenosis when compared to EBD alone. There was not a difference in luminal size between stent and non-stented rabbits at the six-week end point. Histologically, however, overall the use of bioabsorbable UHD-Mg alloy stenting elicited a greater tissue response at the level of the superficial mucosa rather than fibrosis of the lamina propria seen in the stented rabbits. This suggests more favorable healing and less of a tendency towards fibrosis and stenosis even though there may not be a benefit from a luminal size standpoint during this early healing period. Compared to known complications of currently available non-bioabsorbable metal or silicone-based stents, this proof-of-concept investigation highlights the potential use of a novel biodegradable UHD-Mg stent as a therapeutic modality for pediatric SGS.

A CO-releasing coating based on carboxymethyl chitosan-functionalized graphene oxide for improving the anticorrosion and biocompatibility of magnesium alloy stent materials

Due to its biofunctions similar to NO, the CO gas signaling molecule has gradually shown great potential in cardiovascular biomaterials for regulating the in vivo performances after the implantation and has received increasing attention. To construct a bioactive surface with CO-releasing properties on the surface of magnesium-based alloy to augment the anticorrosion and biocompatibility, graphene oxide (GO) was firstly modified using carboxymethyl chitosan (CS), and then CO-releasing molecules (CORM401) were introduced to synthesize a novel biocompatible nanomaterial (GOCS-CO) that can release CO in the physiological environments. The GOCS-CO was further immobilized on the magnesium alloy surface modified by polydopamine coating with Zn2+ (PDA/Zn) to create a bioactive surface capable of releasing CO in the physiological environment. The outcomes showed that the CO-releasing coating can not only significantly enhance the anticorrosion and abate the corrosion degradation rate of the magnesium alloy in a simulated physiological environment, but also endow it with good hydrophilicity and a certain ability to adsorb albumin selectively. Owing to the significant enhancement of anticorrosion and hydrophilicity, coupled with the bioactivity of GOCS, the modified sample not only showed excellent ability to prevent platelet adhesion and activation and reduce hemolysis rate but also can promote endothelial cell (EC) adhesion, proliferation as well as the expression of nitric oxide (NO) and vascular endothelial growth factor (VEGF). In the case of CO release, the hemocompatibility and EC growth behaviors were further significantly improved, suggesting that CO molecules released from the surface can significantly improve the hemocompatibility and EC growth. Consequently, the present study provides a novel surface modification method that can simultaneously augment the anticorrosion and biocompatibility of magnesium-based alloys, which will strongly promote the research and application of CO-releasing bioactive coatings for surface functionalization of cardiovascular biomaterials and devices.

Aneurysm healing following treatment with biodegradable embolization materials: assessment in a rat sidewall aneurysm model

BackgroundBiodegradable materials that dissolve after aneurysm healing are promising techniques in the field of neurointerventional surgery. We investigated the effects of various bioabsorable materials in combination with degradable magnesium alloy...

Development and Future Trends of Protective Strategies for Magnesium Alloy Vascular Stents.

Magnesium alloy stents have been extensively studied in the field of biodegradable metal stents due to their exceptional biocompatibility, biodegradability and excellent biomechanical properties. Nevertheless, the specific in vivo service environment causes magnesium alloy stents to degrade rapidly and fail to provide sufficient support for a certain time. Compared to previous reviews, this paper focuses on presenting an overview of the development history, the key issues, mechanistic analysis, traditional protection strategies and new directions and protection strategies for magnesium alloy stents. Alloying, optimizing stent design and preparing coatings have improved the corrosion resistance of magnesium alloy stents. Based on the corrosion mechanism of magnesium alloy stents, as well as their deformation during use and environmental characteristics, we present some novel strategies aimed at reducing the degradation rate of magnesium alloys and enhancing the comprehensive performance of magnesium alloy stents. These strategies include adapting coatings for the deformation of the stents, preparing rapid endothelialization coatings to enhance the service environment of the stents, and constructing coatings with self-healing functions. It is hoped that this review can help readers understand the development of magnesium alloy cardiovascular stents and solve the problems related to magnesium alloy stents in clinical applications at the early implantation stage.

Fucoidan/collagen composite coating on magnesium alloy for better corrosion resistance and pro-endothelialization potential

Magnesium alloy stents (MAS) have broad application prospects in the treatment of cardiovascular diseases. However, poor corrosion resistance and biocompatibility greatly limit the clinical application of MAS. In this work, the coating consisting of MgF2 layer, polydopamine layer, fucoidan and collagen IV was constructed on Mg-Zn-Y-Nd (ZE21B) alloy to improve its corrosion resistance and pro-endothelialization potential. The fucoidan and collagen IV in the coating could obviously enhance the hemocompatibility and pro-endothelialization potential respectively. Compared with bare ZE21B alloy, the fucoidan/collagen composite coating modified ZE21B alloy possessed lower corrosion current density and better corrosion resistance. Moreover, the modified ZE21B alloy exhibited relatively low hemolysis rate, fibrinogen adsorption and platelet adhesion in the blood experiments, suggesting the improved hemocompatibility. Furthermore, the modified ZE21B alloy favorably supported the adhesion and proliferation of vascular endothelial cells (ECs) and effectively regulated the phenotype of smooth muscle cells (SMCs), thus improving the pro-endothelialization potential of vascular stent materials. The fucoidan/collagen composite coating can significantly improve the corrosion resistance and pro-endothelialization potential of ZE21B alloy, showing great potential in the development of degradable MAS.

Synthesizing a multifunctional polymer to construct the catalytically NO-generating coating for improving corrosion resistance and biocompatibility of the magnesium alloy stent materials

Owing to its excellent mechanical properties and biodegradability, magnesium-based alloys have become the research focus of biodegradable cardiovascular materials. However, the in vivo rapid degradation and poor surface endothelial regeneration and repair ability still restrict their clinical applications in the field of vascular stent materials. Nitric oxide (NO), as an endogenous gas signaling molecule, has multiple effects such as anticoagulation, promoting endothelialization, and anti-restenosis, showing a great potential for improving the performances of the cardiovascular materials and devices. In the present study, based on six-arm polyethylene glycol (PEG), a novel anticoagulant polymer (PEG-Hep-SeCA) with the catalytic release of NO was synthesized by successively introducing heparin and selenocystamine, followed by the immobilization of the as-synthesized polymer on the Zn2+-loaded polydopamine coating modified magnesium alloy surface to enhance the anti-corrosion and biocompatibility. The results demonstrated that the PEG-Hep-SeCA polymer coating was uniform and dense, which could not only obviously enhance the anticorrosion and the hydrophilicity of the magnesium alloy, but also selectively promote the bovine serum albumin (BSA) adsorption, thereby significantly improving the endothelial cells (ECs) growth and hemocompatibility. Additionally, the as-prepared polymer coating could effectively catalyze the release of NO from endogenous NO donors, which can further ameliorate the hemocompatibility and ECs growth, as well as enhance the expression of vascular endothelial cell growth factor (VEGF) and NO of the ECs. Therefore, this study opens a new way to construct the multifunctional coating with the ability of catalytic releasing NO on the surfaces of the magnesium-based alloys to simultaneously reduce the corrosion speed, improve the hemocompatibility, and accelerate the reendothelialization.

Effect of unsoluble corrosion products of WE43 alloys in vitro on macrophages.

Magnesium alloys have been used to manufacture biodegradable implants, bone graft substitutes, and cardiovascular stents. WE43 was the most widely used magnesium alloy. The degradation process begins when the magnesium alloy stent is implanted in the body and comes into contact with body fluid. The degradation products include hydrogen, Mg2+ , local alkaline environment, and unsoluble products. A large number of studies focused on Mg2+ and pH in vitro, and in vivo of magnesium alloys, but few studies on unsoluble corrosion products (UCPs). In this study, UCPs of WE43 alloy were prepared by immersion in vitro, and their effects on macrophages were investigated. The results showed that the unsoluble corrosion products were Mg24Y5, Mg12YNd, and MgCO3 ·3H2 O, which were dose-dependent on the apoptosis and necrosis of macrophages. After phagocytosis of UCPs, macrophages mainly metabolize in lysosome, and autophagy also participates in the metabolism of UCPs. It also decreases mitochondrial membrane potential and increases lysosomes, endoplasmic reticulum stress, and P2X7 receptor activation. These will increase reactive oxygen species (ROS) in cells, activating NLRP3 inflammatory corpuscles, activating the downstream pro-IL18 and pro-IL1β, and converting it to IL-18, and IL-1β. However, its pro-inflammatory effect is far lower than that of the classical Lipopolysaccharide (LPS) pro-inflammatory pathway. This work has increased our understanding of magnesium alloy metabolism and provides new ideas for the clinical application of magnesium alloys.

Poly(l-lactide)/polycaprolactone based multifunctional coating to deliver paclitaxel/VEGF and control the degradation rate of magnesium alloy stent

Despite significant advancements made in cardiovascular stents, restenosis, thrombosis, biocompatibility, and clinical complications remain a matter of concern. Herein, we report a biodegradable Mg alloy stent with a dual effect of the drug (Paclitaxel) and growth factor (VEGF) release. To mitigate the fast degradation of Mg alloy, inorganic and organic coatings were formed on the alloy surface. The optimized hierarchal sequence of the coating was the first layer consisting of magnesium fluoride, followed by poly(l-lactide) and hydroxyapatite coating, and finally sealed by a polycaprolactone layer (MgC). PLLA and HAp were used to increase the adhesion strength and biocompatibility of the coating. Paclitaxel and VEGF were loaded in the final PCL layer (Mg-C/PTX-VEGF). As compared to bare Mg alloy (28 % weight loss), our MgC system showed (3.1 % weight loss) successful decrease in the degradation rate. Further, the in vitro biocompatibility illustrated the highly biocompatible nature of our drug and growth factor-loaded system. The in vivo results displayed that the drug loading decreased the inflammation and neointimal hyperplasia as indicated by the α-SMA and CD-68 antibody staining. The growth factor helped in the endothelialization which was established by the FLKI and ICAM antibody staining of the tissue.

Fucoidan-based coating on magnesium alloy improves the hemocompatibility and pro-endothelialization potential for vascular stent application

Biodegradable magnesium alloy stents have great application potential in the treatment of cardiovascular diseases. However, bare magnesium alloy stents are still limited by some problems such as too fast degradation, poor hemocompatibility, and inability to regulate the behaviors of vascular cells in clinical applications. Surface modifications are highly requested to improve the corrosion resistance and biocompatibility of magnesium alloy stents. Herein, a fucoidan-based coating consisting of MgF2 layer, polydopamine (PDA) and fucoidan was constructed on Mg-Zn-Y-Nd (ZE21B) alloy to improve its corrosion resistance, hemocompatibility and rapid endothelialization for vascular stent application. Compared to bare ZE21B alloy, the modified ZE21B alloy exhibited better corrosion resistance and hemocompatibility. More importantly, the endothelial cells (ECs) and smooth muscle cells (SMCs) exhibited a distinct dose-dependent behaviors towards the fucoidan grafting density. The relatively low fucoidan grafting density promoted the proliferation, spreading and migration of ECs, but suppressed these behaviors of SMCs. The results of in vivo implantation experiments indicated that the fucoidan-based coating modified ZE21B alloy can inhibit intimal hyperplasia, relieve tissue inflammation, and promote the rapid endothelialization. Thus, the fucoidan-based coating provides a simple and effective strategy to develop novel magnesium alloy stents with improved corrosion resistance, good hemocompatibility and pro-endothelialization potential.

Study on surface quality and mechanical properties of micro-milling WE43 magnesium alloy cardiovascular stent

Traditional laser processing technique is mainly applied for cardiovascular stent manufacture, especially for materials with high mechanical properties and high melting point, while it usually produces problems such as material ablation and defects during finish machining process. Magnesium alloy, as material candidate for bioresorbable cardiovascular stent, has low melting and ignition point, high oxidizability property. Laser processing technique scarcely meets the requirements of high surface quality of magnesium alloy cardiovascular stents, this paper firstly develops a five-axis micro-milling technique to fabricate magnesium alloy cardiovascular stents. Milling orthogonal test was carried out to obtain the optimal finish machining parameters, and then a novel stent machining process was established. The processed stent has an inner diameter of 1.5 mm, a thickness of 80 μm and a length of 8 mm with a U-bend width of 100 μm and a link strut width of 70 μm, and the optimal finish processing parameters was set up with the main spindle speed of 30,000 rpm, feed speed 200 mm/min, cutting width 50 μm and cutting depth 40 μm. The dimensional accuracy and surface topography of the magnesium alloy stent were measured and characterized, and results showed that the dimensional accuracy was within 0.01 mm, and the machined stent achieved better surface quality without obvious processing defects such as pits, grooves and pores while comparing with the stent under original processing parameters. In order to evaluate the radial support performance of the stent, the radial compression and expansion experiments and simulations were conducted, respectively. Results showed that the maximum diameter error in the experiment and simulation was 13.35 %, and the radial recoiling error was 16.79 %. This work provides a potential stent manufacture technique in the development and clinical application of bioresorbable magnesium alloy stent.

Copper-loaded chitosan coating for improved in-vitro corrosion resistance and endothelialization of magnesium alloy stents

For degradable magnesium alloy stents, excellent corrosion resistance and rapid endothelialization are two essential properties. In this paper, we plan to use a copper-loaded chitosan coating to accelerate the endothelialization process of the stent, which not only improves the biocompatibility of the magnesium alloy stent, but also its corrosion resistance by improving the service environment in vivo. Copper is an impurity in magnesium alloys, so how copper-containing coatings affect the corrosion resistance of magnesium alloy stents is the focus of this paper. The corrosion properties of the material were characterized by electrochemical experiments, immersion experiments, and in vitro cellular experiments characterized the effect of the copper-loaded coating on endothelial cells. The results showed that the Icorr of the copper-loaded chitosan coated sample and the Icorr of the unloaded copper chitosan coated sample were both in the order of 10−8, and the decrease of the corrosion resistance of the magnesium alloy by the copper-containing chitosan composite coating was not significant, and it still had a protective effect on the magnesium alloy substrate. During the immersion process, magnesium and copper ions were slowly released, followed by the hydrogen released. In addition, the weight loss rate of different coated samples presented the tendency of slower at inital, faster at last, and the weight loss rate of 0.041% for the copper-loaded chitosan coated sample was not significantly different from that of 0.035% for the unloaded copper coating group, after 28 days of immersion. The in vitro degradation products of the copper-loaded composite coating on the surface of magnesium alloy were also analyzed by XRD and EPMA, which included Mg(OH)2, Mg3(PO4)2 and Ca3(PO4)2; in addition the degradation process was analyzed. The cellular experiments results showed that the copper-loaded magnesium alloy had a proliferation rate of 243.0% for endothelial cells, which indicated that the copper-loaded coating could endow magnesium alloy stent a good biofunctional properties.

A novel MgF2/PDA/S-HA coating on the bio-degradable ZE21B alloy for better multi-functions on cardiovascular application

Recently, functional molecules such as Polydopamine (PDA), Hyaluronic Acid (HA) and heparin have been widely studied in the field of surface modification of magnesium (Mg) alloy stents for better degradation behavior and biocompatibility, but their further application is limited by undesirable anticoagulant function, uncontrollable degradation and easy bleeding, respectively. Regarding to this consideration, a magnesium Fluoride/Polydopamine/Sulphonated hyaluronic acid (MgF 2 /PDA/S-HA) composite coating was successfully prepared by applying S-HA with sulfur content of 9.71 wt% on the surface of ZE21B alloy in this study. The results showed that the composite coating with a unique mesh structure not only inherited the anticoagulant effect of sulfonic acid group and the excellent cyto-compatibility of S-HA with high sulfur content, but also significantly improved the corrosion performance of ZE21B alloy. These results indicate a great application potential of the composite coating in the field of cardiovascular biomaterials.

Recent advances in surface endothelialization of the magnesium alloy stent materials

Magnesium and its alloy have good mechanical properties and biodegradability, and have become the hotspot of the next-generation biodegradable vascular stent materials. However, their rapid degradation in vivo and poor biocompatibility are still the bottlenecks of clinical applications for the cardiovascular stents. In particular, how to induce the repair and regeneration of the vascular endothelial with normal physiological functions on the surface of the magnesium alloy stent materials represents the key to its clinical application in the field of cardiovascular stents. It has been believed that it is an ideal way to completely solve the postoperative complications through constructing the multifunctional anti-corrosive bioactive coating on the magnesium alloy surface to induce the formation of vascular endothelium with normal physiological functions. However, how to construct a corrosion-resistant multifunctional bioactive coating with the good endothelial regeneration abilities on the magnesium alloy surface still faces a great challenge. This paper mainly focused on highlighting and summarizing the recent advances in the surface endothelialization of the magnesium alloy materials for the vascular stent, including the bio-inert coating, in-situ immobilization of bioactive molecules on the surface, polymer coating loaded with bioactive factors, novel multifunctional polymer coating, bioactive micropatterns, bioactive layer with glycocalyx-like structure, NO-releasing coating and bioactive sol-gel coating. The advantages and disadvantages of these strategies were discussed and analyzed. Finally, in the senses of future development and clinical application, this paper analyzed and summarized the development direction and prospect of surface endothelialization of the magnesium alloy vascular stents. It is anticipated that this review can give the new cues to the surface endothelialization of the cardiovascular magnesium alloy stents and promote future advancements in this field.

Corrosion resistance evaluation of biodegradable magnesium alloy vascular stents optimized by mechanical adapted polymer coating strategy

Surface modification coating of magnesium alloy stents as a physical barrier is to inhibit the corrosive medium from contact with matrix. In view of the complex deformation behavior of stent, mechanical adopted polymer coating strategy was considered in our work. Here, a relatively high plasticity polymer- poly(butyl acrylate) (PBA) was applied as the outer protective layer on the surface of magnesium alloy discs and stents through a dip-coating method and ultrasonic spraying system respectively. Compared with low plasticity poly(d,l-lactide) (PDLLA) control group, mechanical property of PBA polymer film were detected, furthermore, the static corrosion behaviors of PBA/MgF2 flake samples were investigated by electrochemical and immersion tests for a period time. The morphologies and degradation behaviors of stents after grip-expansion were conducted to explore the mechanical adaptability of PBA/MgF2 coating with magnesium alloy stent. PBA/MgF2 composite coating could improve the corrosion resistance of both static and deformed magnesium alloys, exhibiting a long-term protection. Especially, PBA-coated stent maintained the structural integrity and a relatively smooth surface after 21 days of service. Therefore, it is inferred that a coating material with high elongation at break is more mechanical adaptability with stent deformation to reduce the degradation rate of magnesium alloy stents.

Dual strengthened corrosion control of biodegradable coating on magnesium alloy for vascular stent application

Recently, magnesium alloy vascular stents have aroused great attraction because of their biodegradability and good mechanical properties. However, the rapid degradation of magnesium alloy stents causes their premature collapse in clinical application. So far, there have been few magnesium alloy stent systems that achieved sufficient support time by using biodegradable coating. In this paper, a dual strengthened biodegradable coating on a AZ31b magnesium alloy stent was suggested to achieve stronger adhesion and lower water permeability. The composite coating consisted of a magnesium hydrate - magnesium fluoride (Mg(OH)2-MgF2) inorganic base layer constructed by a simple two-step solution immersion and a graphene oxide - poly(trimethylene carbonate) outer layer prepared by ultrasonic spraying. The biodegradable composite coating modified magnesium alloy exhibited an extremely low corrosion current density of 4.3 × 10−10 A·cm−2, which is five orders of magnitude lower than the unmodified magnesium alloy. In vitro immersion tests revealed that the modification can effectively reduce the corrosion rate of the magnesium alloy stent, and the modified magnesium alloy stent can support at least 8 weeks. Furthermore, in vitro biological experiment revealed the modification of the composite coating improved the biocompatibility and ensured good microenvironment for vascular repair. These results suggest that the biodegradable composite coating has great potential for application in vascular stent.

One-step fabrication of self-healing poly(thioctic acid) coatings on ZE21B Mg alloys for enhancing corrosion resistance, anti-bacterial/oxidation, hemocompatibility and promoting re-endothelialization

Coating magnesium (Mg) alloy stents with biodegradable polymeric materials can address the problems of thrombosis, inflammation, and restenosis caused by poor corrosion resistance and delayed endothelialization; however, these commonly used polymer coatings and their degradation products have no therapeutic effect and sometimes bring extra-side effects. Herein, to develop a polymeric coating with an additional therapeutic effect from that of the polymer itself, a poly(thioctic acid)-based homopolymer was simply synthesized via solvent-free thermal polymerization (containing Zn2+ ions) of thioctic acid (TA), a bioactive ingredient originating from the human body. A Poly(TA-Zn) coating was fabricated on alkali-heat (Mg(OH)2) treated ZE21B alloys via a one-step method, followed by conjugating REDV peptides, to simultaneously enhance the corrosion resistance and re-endothelialization process. Surface characterization and performance were comprehensively investigated. Molecular dynamics (MD) simulations demonstrate that the Zn-O coordination bonds formed between Zn2+ ions and carboxylic groups can inhibit the depolymerization of the Poly(TA-Zn) polymer. SEM micrographs show that the Poly(TA-Zn) coating is homogeneous and has a thickness of 45.03 ± 4.85 μm, and this coating is sturdily bonded to the Mg(OH)2 modified ZE21B substrate. Electrochemical and immersion tests show that the Poly(TA-Zn) sample provides good corrosion protection for ZE21B substrates because of its excellent self-healing properties, and it exhibits superior anti-bacterial/oxidation properties. After immobilizing REDV peptides, Poly(TA-Zn)-REDV samples can substantially hinder platelet adhesion/activation, reduce hemolysis rate, selectively promote the proliferation of endothelial cells and inhibit the growth of smooth muscle cells, thereby improving the anti-coagulation and re-endothelialization ability of Mg substrates.

Enhanced corrosion resistance and biocompatibility of an elastic poly (butyleneadipate-co-terephthalate) composite coating for AZ31 magnesium alloy vascular stents

Surface modification has been considered to provide an effective solution to the poor corrosion resistance of magnesium alloys. A large number of relevant studies have demonstrated that various protective coatings can reduce the degradation rate of magnesium alloys, but most of them are for magnesium alloy materials and devices without deformation. For biodegradable magnesium alloy stents, the selection of protective coating is vitally important due to the residual stress during implantation and cyclic loading after implantation. Therefore, compared with commonly used poly-D,l-lactide (PDLLA), a reliable protection was proposed on HF-treated Mg alloy via application of poly(butyleneadipate-co-terephthalate) (PBAT) with high elongation at break in this paper. In the long term, the corrosion resistance of PBAT-F coating of both flake samples and stents was decisively superior to PDLLA, which could be attributed to its outstanding barrier performance and mechanical properties. Simultaneously, PBAT composite coating exhibited better hemocompatibility and higher cell proliferation rates. The above results show that PBAT is an excellent coating material for vascular stents whereas PBAT composite coating could be a promising candidate as a protective coating for Mg stents.

Preparation of functional coating on magnesium alloy with hydrophilic polymers and bioactive peptides for improved corrosion resistance and biocompatibility

• 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.

Optimizing structural design on biodegradable magnesium alloy vascular stent for reducing strut thickness and raising radial strength

Thinner biodegradable magnesium alloy stents (BMgSs) afford faster endothelialisation to delay degradation and better clinical performance. However, compared with traditional non-degradable stents, thin-walled BMgS structures are prone to challenges, such as insufficient support capacity and fracture, during immediate expansion due to low elastic modulus and ultimate elongation. In this study, a thin-walled BMgS structure was optimised. A ZE21B alloy with large breaking elongation and excellent mechanical properties served as the basis of our BMgS. Using finite element analysis, the support ring structure of a typical stent BioMatrix was optimised using response surface models, and an optimised configuration of a thin-walled BMgS was obtained. The optimised thin-walled stent (100-μm thick) had a radial strength comparable to that of the original thick-walled stent (150-μm thick); and the maximum principal strain is significantly decreased (0.207 vs 0.283). The balloon dilation and radial strength tests were validated. Experiments showed that the optimised stent had sufficient deformation stability during the crimping and expansion processes, and there was no strut fracture. Furthermore, the maximum principal stress area of the stent and the damage to the stenotic artery were significantly improved after optimisation.