Magnesium-based Implants Research Articles

Biocompatibility and mechanical performance of magnesium alloys for biomedical application- a state of the art review

This review addresses the problems associated with various types of implants, providing a brief background on their challenges and surgical implications. Preclinical and clinical studies are discussed to understand the causes of implant failures. The review specifically examines the potential of magnesium-based alloys in biomedical applications, focus on existing research to offer a comprehensive overview of their advantages and disadvantages in biodegradable implants. It explores how alloying elements can enhance mechanical properties and corrosion behavior in Mg alloys. This review indicates how specific percentages of different alloying elements, combined with suitable manufacturing and post-processing techniques, can yield optimized results. Additionally, the review assesses the impact of magnesium alloy degradation on the healing process and suggests strategies to mitigate adverse effects. By thoroughly analyzing the literature, this paper offers valuable insights into fabricating magnesium-based implants to achieve ideal mechanical and corrosion properties, enhancing their effectiveness in biomedical applications.

Zinc-doped phosphate coatings for enhanced corrosion resistance, antibacterial properties, and biocompatibility of AZ91D Mg alloy

Magnesium and its alloys have been foreseen as promising bone-implant owing to good biocompatibility, high strength, mechanical properties, and biodegradability to replace the conventional bio-metals (Titanium, stainless-steel, Co-Cr alloys) in orthopedic applications. However, high corrosion rate and high degradation rates adversely effects like abrupt evolution of H2 gas and localized alkalization in a physiological environment limit its medical applications. To overcome these issues, phosphate-based surface coating is developed on Mg-alloy to resist the high biodegradation and corrosion rate utilizing magnesium substrate as source of magnesium ion through a single-step hydrothermal process. Controlling the fast corrosion rate and localized alkalization would reduce the antibacterial character of magnesium-based implants therefore, the simple phosphate-based coatings has been induced by doping it with zinc ions due to its physiological tolerance and excellent antibacterial efficacy. The doping of zinc ions may provide a sustained drug-free antibacterial characteristic for potential application in orthopedics. The synthesized phosphate-based coating was characterized using advanced techniques like Scanning Electron Microscopy, X-ray Diffraction, and wettability test, followed by comprehensive electrochemical testing to assess its corrosion behavior. The in vitro immersion test in simulated body fluid (SBF) indicates that deposition of phosphate and zinc doped phosphate coatings reduces the degradation rate consequently minimized the fast dissolution of Mg2+ ions and OH- in physiological environment. Additionally, cytotoxicity and biocompatibility were evaluated using Alamar Blue and live/dead assays on the MC3T3-E1 mouse osteoblast cell line. These assays demonstrated good cell viability, indicating the coatings possess favorable cytocompatibility and support cellular metabolic activity.

Improvement of biological and corrosion behavior of plasma electrolytic oxidized Mg implant by 3D printed scaffold of amine-terminated PEG/PCL loaded with dexamethasone

Although magnesium-based implants have good biocompatibility and biodegradability, they suffer from rapid corrosion in the body environment, which limits their biomedical applications. This study represents an approach for designing a bioactive and anti-corrosive hybrid structure composed of an inorganic layer by plasma electrolytic oxidation process and an organic layer of 3D printed polycaprolactone and amine-terminated polyethylene glycol scaffold containing dexamethasone. The results indicated that the hybrid layer exhibited superior adhesion strength, high corrosion resistance, remarkable biocompatibility, cell attachment, and osteogenic differentiation. The dexamethasone released from the 3D printed scaffold revealed high osteogenic differentiation capability. Hence, the fabrication of plasma electrolytic oxidized interlayer with a 3D printed scaffold can be a novel platform to preserve the magnesium-based biological implants from corrosion and to regenerate bone along with the controlled release of osteogenic components.

Sheep Bone Ultrastructure Analyses Reveal Differences in Bone Maturation around Mg-Based and Ti Implants.

Magnesium alloys are some of the most convenient biodegradable materials for bone fracture treatment due to their tailorable degradation rate, biocompatibility, and mechanical properties resembling those of bone. Despite the fact that magnesium-based implants and ZX00 (Mg-0.45Zn-0.45Ca in wt.%), in particular, have been shown to have suitable degradation rates and good osseointegration, knowledge gaps remain in our understanding of the impact of their degradation properties on the bone's ultrastructure. Bone is a hierarchically structured material, where not only the microstructure but also the ultrastructure are important as properties like the local mechanical response are determined by it. This study presents the first comparative analysis of bone ultrastructure parameters with high spatial resolution around ZX00 and Ti implants after 6, 12, and 24 weeks of healing. The mineralization was investigated, revealing a significant decrease in the lattice spacing of the (002) Bragg's peak closer to the ZX00 implant in comparison to Ti, while no significant difference in the crystallite size was observed. The hydroxyapatite platelet thickness and osteon density demonstrated a decrease closer to the ZX00 implant interface. Correlative indentation and strain maps obtained by scanning X-ray diffraction measurements revealed a higher stiffness and faster mechanical adaptation of the bone surrounding Ti implants as compared to the ZX00 ones. Thus, the results suggest the incorporation of Mg2+ ions into the bone ultrastructure, as well as a lower degree of remodeling and stiffness of the bone in the presence of ZX00 implants than Ti.

An amorphous Si-O-N coating on magnesium to retard corrosion & improve biocompatibility

Fast corrosion and the resulting adverse biological responses impede the applications of magnesium-based implants. Here, an amorphous Si-O-N coating is prepared on Mg via radio frequency plasma-enhanced chemical vapor deposition (PECVD) to address those issues. This coating is compact and uniform, which can firmly adhere to the substrate. It provides efficient shielding, thus reduces corrosion rate from 36.16 μm/y to 16.14 μm/y. The coating itself is biocompatible, and coated Mg exhibits excellent biocompatibility to rat/mouse mesenchymal stem cells. PECVD-obtained amorphous coatings based on biocompatible elements could be a solution for Mg-based implants.

Mechanical and Computational Fluid Dynamic Models for Magnesium-Based Implants.

Today, mechanical properties and fluid flow dynamic analysis are considered to be two of the most important steps in implant design for bone tissue engineering. The mechanical behavior is characterized by Young's modulus, which must have a value close to that of the human bone, while from the fluid dynamics point of view, the implant permeability and wall shear stress are two parameters directly linked to cell growth, adhesion, and proliferation. In this study, we proposed two simple geometries with a three-dimensional pore network dedicated to a manufacturing route based on a titanium wire waving procedure used as an intermediary step for Mg-based implant fabrication. Implant deformation under different static loads, von Mises stresses, and safety factors were investigated using finite element analysis. The implant permeability was computed based on Darcy's law following computational fluid dynamic simulations and, based on the pressure drop, was numerically estimated. It was concluded that both models exhibited a permeability close to the human trabecular bone and reduced wall shear stresses within the biological range. As a general finding, the proposed geometries could be useful in orthopedics for bone defect treatment based on numerical analyses because they mimic the trabecular bone properties.

Superior toughness Anticorrosion-Bioactive integrated multilayer coating with excellent adhesion for biodegradable Magnesium-Based stents

Biodegradable magnesium-based stents overcome the limitations of non-degradable stents and exhibit superior mechanical properties compared to biodegradable polymer counterparts, representing an inevitable trend in cardiovascular stent evolution. However, the excessively rapid degradation rate remains a pivotal factor that constrains their clinical application. In this work, an anticorrosion-bioactive integrated multilayer coating is developed for magnesium-based stents. By optimizing the molecular structure of poly(L-lactide-co-ω-caprolactone) (PLCL), a biodegradable coating material with excellent mechanical properties and effective barrier performance is obtained. To enhance the wettability and adhesion strength between the highly surface-energy magnesium and the low-polarity PLCL, a silane-based transition layer and an intermediate connecting layer of covalently bonded PLCL chains are sequentially constructed on the magnesium substrate. Furthermore, bioactive polymer brush consists of poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) and Arg-Glu-Asp-Val (REDV) peptide is fabricated on the PLCL anticorrosion coating. The combined in vitro and in vivo experiments confirm that the multilayer coating exhibits commendable anti-corrosion performance, and is beneficial to anticoagulation and endothelialization, thereby making the degradation process of magnesium-based stents more compatible with the vascular remodeling process. The anticorrosion-bioactive multilayer composite coating developed in this study has the potential to overcome the corrosion resistance limitations of magnesium-based implants, thus promoting their clinical application.

Unveiling the Effect of Particle Incorporation in PEO Coatings on the Corrosion and Wear Performance of Magnesium Implants

Magnesium has been a focal point of significant exploration in the biomedical engineering domain for many years due to its exceptional attributes, encompassing impressive specific strength, low density, excellent damping abilities, biodegradability, and the sought-after quality of biocompatibility. The primary drawback associated with magnesium-based implants is their susceptibility to corrosion and wear in physiological environments, which represents a significant limitation. Research findings have established that plasma electrolytic oxidation (PEO) induces substantial modifications in the surface characteristics and corrosion behavior of magnesium and its alloy counterparts. By subjecting the surface to high voltages, a porous ceramic coating is formed, resulting in not only altered surface properties and corrosion resistance, but also enhanced wear resistance. However, a drawback of the PEO process is that excessive pore formation and porosity within the shell could potentially undermine the coating’s corrosion and wear resistances. Altering the electrolyte conditions by introducing micro- and nano-particles can serve as a valuable approach to decrease coating porosity and enhance their ultimate characteristics. This paper evaluates the particle adhesion, composition, corrosion, and wear performances of particle-incorporated coatings applied to magnesium alloys through the PEO method.

Construction of a PEO/Mg–Mn LDH composite coating on Mg–Ag–Mn alloy for enhanced corrosion resistance and antibacterial potential

Endowing magnesium alloys with both durable antibacterial ability and reliable corrosion resistance is an urgent task for the development of magnesium-based implants. In this work, Mg–Mn layered double hydroxide (LDH) intercalated with organic salicylic acid (SA) anion was synthesized on a PEO-coated Mg–Ag–Mn alloy via the combination of co-precipitation and hydrothermal treatments. The PEO layer endows Mg–Ag–Mn alloy with a moderate corrosion barrier and the Mg–Mn LDH layer not only seals the PEO defects, but also acts as a reservoir for antibacterial agents (namely SA). The PEO/Mg–Mn LDH composite coating on Mg–Ag–Mn alloy dramatically increases its corrosion resistance by up to 3 orders of magnitudes, which also tailors the ionic release kinetics for a desired antibacterial potential to prevent bacterial infection.

Bone regeneration and antibacterial properties of calcium-phosphorus coatings induced by gentamicin-loaded polydopamine on magnesium alloys

Improving the corrosion resistance, osteogenic activity, and antimicrobial capacity of the magnesium-based implant is considered the key to promoting their large-scale clinical application. In this study, we reported a novel calcium-phosphorus coating induced by gentamicin (G)-loaded polydopamine for the surface treatment of the magnesium alloy. According to material characterization, immersion tests, and electrochemical analysis, the composite coating has a dense structure and a high crystallinity for greater corrosion resistance. Meanwhile, drug release and antimicrobial experiments demonstrated that the magnesium matrix loaded with gentamicin showed strong inhibition of Escherichia coli and Staphylococcus aureus, and the calcium-phosphorus coating further prolonged the release profile of G, which would contribute to the long-term bactericidal activity of the magnesium implants. In addition, the coating significantly promoted the adhesion, proliferation, and osteogenic differentiation ability of MC3T3-E1. The results of in vivo experiments confirmed that magnesium alloys with composite coatings significantly promoted bone regeneration under infected conditions. This study provides a promising strategy for the development of multifunctional magnesium-based implants with good corrosion resistance, and antibacterial and osteogenic capabilities.

Effect of Magnesium as Biomaterial in Biodegrdation

Since many years ago, the study of engineering materials—which includes metal alloys, composites, polymers, ceramics, and metallic glasses—has advanced significantly, particularly in the area of biomaterials. Due to their excellent biocompatibility and unique mechanical qualities, alloys derived on magnesium (Mg) now have a wide array of uses in the biomedical sector. By combining Mg with other elements including nanoparticles, polymers, Zinc, Yttrium and Manganese are included with capability to perform suitable reactions. Addictive manufacturing allows the porosity of the scaffolds to be adjusted, allowing for fine-tuning of the scaffold degradation performance and cell response. Specialized equipment will be required to print magnesium in an inert atmosphere while maintaining safe material handling. As a result, due to inherent characteristics of magnesium mixes, such as a higher vapour pressure and a stronger inclination to oxidize, the additive manufacture of disposable magnesium-based implants presents certain challenges. Inadvertent degradation, structural failure, hydrogen evolution, alkalization, and cytotoxicity are caused by the high corrosion rate of Mg-based implants. A number of methods, such as the design of a magnesium alloy and the alteration of the surface properties, are employed to tailor the degradation rate since it is envisaged that biodegradable Mg-based implants will demonstrate regulated degradation and satisfy the needs of specific applications. Biodegradation mechanism along with its controlling aspects and improvement measures with respect to biodegradation are reviewed in this paper.

Biochemical aspects of magnesium-enhanced bone regeneration

Current research is focused on practical implications of magnesium-based implants largely due to their biodegradability and ability to promote bone healing and formation. However, the mechanism underlying the osteogenesis regulation by magnesium is still unclear.We describe cellular and molecular mechanisms underlying the effect of magnesium ions (Mg2+) on bone growth following the device implantation. The presented data demonstrate magnesium-induced activation of canonical Wnt/β-catenin signaling pathway in human bone marrow stromal cells resulting in their differentiation into osteoblasts, osteogenic effect and recovery of bone defects. We describe the role of the molecular mechanisms responsible for osteopromotive properties of Mg2+ and associated with unique transient receptor potential melastatin 7 (TRPM7) cation channels mediating the Mg2+ influx. TRPM7-mediated Mg2+ influx is important for platelet-derived growth factor (PDGF)-induced proliferation, adhesion, and migration of human osteoblasts, as well as for promotion of Mg2+-associated bone regeneration.We discuss the effect of Mg2+ on intracellular signaling processes, expression of the vascular endothelial growth factor (VEGF), hypoxia-inducible factor-2α, and peroxisome proliferator-activated receptor-γ coactivator 1α. Mg2+ can promote bone regeneration by enhancing the production of type X collagen and VEGF by osteogenic cells in bone marrow.

Polymer bilayer-Micro arc oxidation surface coating on pure magnesium for bone implantation.

Pure magnesium-based ortho-implants have a number of advantages. However, vital parameters like degradation rate and biocompatibility still call for significant improvement. In this study, poly (1,3-trimethylene carbonate) (PTMC) and polydopamine (PDA) bilayer and micro arc oxidation composite coatings were prepared successively on magnesium surface by immersion method and microarc oxidation. Its corrosion resistance and biocompatibility were evaluated by in vitro corrosion tests, cellular compatibility experiments, and in vivo animal experiments. In vitro experiments demonstrated that the composite coating provides excellent corrosion protection and biocompatibility. Animal studies demonstrated that the composite coating slowed the degradation of the implant and was not toxic to animal viscera. In conclusion, the inorganic-organic composite coating proposed in this study provided good corrosion resistance and enhanced biocompatibility for pure magnesium implants. The translational potential of this article is to develop an anti-corrosion composite coating on a pure magnesium surface and to verify the viability of its use in animal models. It is hoped to open up a new approach to the design of new degradable orthopedic magnesium-based implants.

Long-term in vivo degradation of Mg–Zn–Ca elastic stable intramedullary nails and their influence on the physis of juvenile sheep

The use of bioresorbable magnesium (Mg)-based elastic stable intramedullary nails (ESIN) is highly promising for the treatment of pediatric long-bone fractures. Being fully resorbable, a removal surgery is not required, preventing repeated physical and psychological stress for the child. Further, the osteoconductive properties of the material support fracture healing. Nowadays, ESIN are exclusively implanted in a non-transphyseal manner to prevent growth discrepancies, although transphyseal implantation would often be required to guarantee optimized fracture stabilization. Here, we investigated the influence of trans-epiphyseally implanted Mg–Zinc (Zn)–Calcium (Ca) ESIN on the proximal tibial physis of juvenile sheep over a period of three years, until skeletal maturity was reached. We used the two alloying systems ZX10 (Mg-1Zn-0.3Ca, in wt%) and ZX00 (Mg-0.3Zn-0.4Ca, in wt%) for this study. To elaborate potential growth disturbances such as leg-length differences and axis deviations we used a combination of in vivo clinical computed tomography (cCT) and ex vivo micro CT (μCT), and also performed histology studies on the extracted bones to obtain information on the related tissue. Because there is a lack of long-term data regarding the degradation performance of magnesium-based implants, we used cCT and μCT data to evaluate the implant volume, gas volume and degradation rate of both alloying systems over a period of 148 weeks. We show that transepiphyseal implantation of Mg–Zn–Ca ESIN has no negative influence on the longitudinal bone growth in juvenile sheep, and that there is no axis deviation observed in all cases. We also illustrate that 95 % of the ESIN degraded over nearly three years, converging the time point of full resorption. We thus conclude that both, ZX10 and ZX00, constitute promising implant materials for the ESIN technique.

Fixace osteochondrálních fragmentů kolena biodegradabilními implantáty z hořčíkové slitiny u dětských pacientů

PURPOSE OF THE STUDY Fixation of osteochondral fragments are relatively common procedures in pediatric orthopaedic surgery. The use of biodegradable magnesium implants in these indications appears to be a promising alternative to polymer implants due to their favorable mechanical properties and biological behavior. The purpose of this study is to evaluate the short-term clinical and radiological outcomes of the fixation of unstable or displaced osteochondral fractures and osteochondritis dissecans lesions in the knee joint using MAGNEZIX® screws and pins in pediatric patients. MATERIAL AND METHODS In this study, 12 patients (5 girls, 7 boys) were included. The inclusion criteria were as follows (1) age below 18 years; (2) unstable or displaced osteochondral fragments secondary to trauma or as a result of osteochondritis dissecans, Grades III and IV in the ICRS (International Cartilage Repair Society) score, confirmed by imaging methods and indicated for surgical fixation; (3) fixation performed using screws or pins made of the magnesium-based MAGNEZIX® alloy; (4) minimum postoperative interval of 12 months. X-rays and clinical evaluation were assessed 1 day, 6 weeks, 3, 6, and 12 months after the operation. MRIs were performed 1-year postoperatively for evaluation of bone response and degradation behavior of implants. RESULTS The mean age at surgery was 13.3 ± 1.6 years. A total of 25 screws were used in 11 patients, a mean of 2.4 ± 1 per patient, 4 pins were used in 1 patient. In 2 patients, fixation with screws was complemented with fibrin glue. The mean follow-up was 14.2 ± 3.3 months. All patients exhibited complete functional recovery while showing no signs of pain at 6 months postoperatively. No adverse local reactions were observed. At 1-year follow-up, no implant failure has been reported. Complete radiographic healing occurred in 12 cases. Mild radiolucent zones were observed around the implants. CONCLUSIONS The use of screws and pins MAGNEZIX® has been found to provide satisfactory outcomes in terms of fracture healing and very good functional outcomes at 1 year postoperatively. Key words: biodegradable implants, magnesium-based implants, osteochondral fracture, osteochondritis dissecans, MAGNEZIX®.

Composite bone-implant engineered with magnesium and variable degradation for orthopaedics

Metallic biomaterials are suitable for load-bearing scaffolds, and magnesium (Mg) alloy is the most preferable because of its mechanical properties are comparable to those of hard tissue (bone). The most important characteristic of an implant is its biocompatibility and Mg fully satisfies this standard. Mg is also biodegradable, thereby avoiding the need for secondary surgery. An uncontrollable degradation rate is one of the most significant limitations of magnesium-based implants, which hinders their applications in bone tissue engineering. Hydroxyapatite (HAP), a bioactive material, was incorporated into a magnesium metal matrix as a catalyst for enhancing bone tissue regeneration. Porosity in the scaffold could serve as a conduit for nutrients and also aids in the scaffold's weight reduction. This study investigated the effect of selective alloying elements (Ca, Zn, and Fe) on the biodegradability of scaffolds. Powder metallurgy was used to produce the magnesium alloy scaffolds. A calculated quantity of porogen particles, carbamide (urea), was incorporated into the Mg-Ca-Zn-Fe matrix in order to achieve 30% and 50% porosity. Due to the formation of Mg-Ca-Zn-Fe intermetallic compounds, the current study establishes that Mg alloy-based samples exhibit favorable biodegradation behavior. After seven days of immersion, the pH of the immersion liquid had also been found to have stabilized. Consequently, the observations suggest that the biodegradation behavior of bone implants could be modified by developing composite porous magnesium alloy implants.

In Vivo Analysis of a Biodegradable Magnesium Alloy Implant in an Animal Model Using Near-Infrared Spectroscopy

Biodegradable magnesium-based implants offer mechanical properties similar to natural bone, making them advantageous over nonbiodegradable metallic implants. However, monitoring the interaction between magnesium and tissue over time without interference is difficult. A noninvasive method, optical near-infrared spectroscopy, can be used to monitor tissue's functional and structural properties. In this paper, we collected optical data from an in vitro cell culture medium and in vivo studies using a specialized optical probe. Spectroscopic data were acquired over two weeks to study the combined effect of biodegradable Mg-based implant disks on the cell culture medium in vivo. Principal component analysis (PCA) was used for data analysis. In the in vivo study, we evaluated the feasibility of using the near-infrared (NIR) spectra to understand physiological events in response to magnesium alloy implantation at specific time points (Day 0, 3, 7, and 14) after surgery. Our results show that the optical probe can detect variations in vivo from biological tissues of rats with biodegradable magnesium alloy "WE43" implants, and the analysis identified a trend in the optical data over two weeks. The primary challenge of in vivo data analysis is the complexity of the implant interaction near the interface with the biological medium.

High Complication Rate and High Percentage of Regressing Radiolucency in Magnesium Screw Fixation in 18 Consecutive Patients.

(1) Background: Magnesium-based implants use has become a research focus in recent years. Radiolucent areas around inserted screws are still worrisome. The objective of this study was to investigate the first 18 patients treated using MAGNEZIX® CS screws. (2) Methods: This retrospective case series included all 18 consecutive patients treated using MAGNEZIX® CS screws at our Level-1 trauma center. Radiographs were taken at 3-, 6- and 9-month follow-ups. Osteolysis, radiolucency and material failure were assessed, as were infection and revision surgery. (3) Results: Most patients (61.1%) had surgery in the shoulder region. Radiolucency regressed from 55.6% at 3-month follow-ups to 11.1% at 9-month follow-ups. Material failure occurred in four patients (22.22%) and infection occurred in two patients, yielding a 33.33% complication rate. (4) Conclusion: MAGNEZIX® CS screws demonstrated a high percentage of radiolucency that regressed and seems to be clinically irrelevant. The material failure rate and infection rate require further research.

Magnesium-Based Compression Screws in Acute Scaphoid Fractures and Nonunions.

Magnesium-based bioabsorbable osteosynthesis material continues to receive increasing attention. The following study documents our experience with bioabsorbable magnesium screws in scaphoid fracture treatment in hopes to capture further evidence and successful application. Eight acute scaphoid fractures and four nonunions were treated with the magnesium-based bioabsorbable compression screw MAGNEZIX®. Objective outcome was assessed by X-ray imaging and/or CT scan for bone healing. Clinical assessment was achieved using the modified Mayo Wrist Score. Patient-reported outcome measure was performed threefold via QuickDASH, PRWE, and EQ-5D-5L questionnaires in all patients. Follow-up was 32.5months (SD 18.7) in the acute fracture group and 31months (SD 7.4) in the nonunion group. Bone healing was achieved in all eight patients with acute scaphoid fractures and in three of four patients with scaphoid nonunion. The modified Mayo Wrist Score was 95 (SD 7.1) in fractures and 80 (SD 7.1) in nonunion patients during follow-up. QuickDASH score was 3.9 (SD 5.8) in fracture and 19.3 (SD 10.6) in nonunion patients. All but one patient (87,5%) with scaphoid fractures presented with a full health state during follow-up (EQ-5D-5L). Nonunion patients had problems in 10 out of 19 dimensions in EQ-5D-5L. Acute fractures presented with a score of 3.9 (SD 7.9) and nonunions with a score of 19.7 (SD 32.4) in PRWE total scoring during follow-up. Magnesium-based implants have excellent clinical outcomes when used for scaphoid fractures in eight presented cases and good to moderate clinical outcomes when used for nonunions in three of four presented cases. Additional studies are required to further analyze the differentiated applicability in scaphoid nonunion as well as overall performance when compared to non-absorbable screws in larger cohorts.

A self-healing and bioactive coating based on duplex plasma electrolytic oxidation/polydopamine on AZ91 alloy for bone implants

Magnesium (Mg) alloys are well-known in biomedical materials owing to their elastic module near to bone, biocompatibility and biodegradation properties. Nevertheless, poor corrosion resistance hinders their biomedical applications. Besides, it is necessary to endow Mg alloys with bioactive property, which is crucial for temporary bone implants. Here, a self-healing, corrosion resistant and bioactive duplex coating of plasma electrolytic oxidization (PEO)/polydopamine (PDA) is applied on AZ91 substrate using PEO and subsequent electrodeposition process. Moreover, the role of different electrodeposition times (60 s, 120 s) and dopamine concentrations (1 and 1.5 mg/ml) to improve corrosion resistance, bioactivity, biocompatibility and self-healing property and its mechanism are investigated. The results indicate that the PEO coating is efficiently sealed by the PDA, depending on the electrodeposition parameters. Noticeably, electrodeposition for 120 s in dopamine concentration of 1 mg/ml (120T-1C) results in the formation of uniform and crack-free PDA coating. Duplex PEO/PDA coatings reveal high bioactivity compared to PEO coating, owing to electrostatic interaction between PDA top-layer and calcium and phosphate ions as well as high hydrophilicity of coatings. In addition, duplex PEO/PDA coatings also show improved and more stable protective performance than the PEO and bare alloy, depending on the PDA deposition parameters. Noticeably, the corrosion current density of the 120T-1C decreases one orders of magnitude compared to PEO. In addition, the presence of a broad passivation region in the anodic polarization branch shows durable self-healing property via Zipper-like mechanism, demonstrating the duplex coating could preserve promising corrosion resistance. Furthermore, the cytocompatibility of duplex coated samples is also confirmed via interaction with MG63 cells. In summary, the PEO/PDA coating with great corrosion protection, self-healing ability, bioactivity and biocompatibility could be a promising candidate for degradable magnesium-based implants.