Biofunctionalized anti-corrosive silane coatings for magnesium alloys

The Effect of Surface Functionalization of Magnesium Alloy on Degradability, Bioactivity, Cytotoxicity, and Antibiofilm Activity

Magnesium alloys are promising biomaterials to be used as temporary implants due to their biocompatibility and biodegradability. The main limitation in the use of these alloys is their rapid biodegradation. Moreover, the risk of microbial infections, often following the implant surgery and hard to eradicate, is another challenge. Thus, with the aim of reducing biodegradability and conferring antibiofilm activity, sheets of the magnesium alloy AZ31 were properly modified with the introduction of hydroxy (polyethyleneoxy)propyl silane (PEG) and quaternary ammonium silane chains (QAS). The derivatized sheets were characterized by ATR-FTIR spectroscopy and their performances as concerns their stability, Mg2+ in vitro release, and in vitro bioactivity were evaluated as well. The results showed an increased stability with a reduction in corrosion, a slower Mg2+ ion release, and the formation of hydroxyapatite in the sheets' surface. In addition, cytotoxicity evaluations were carried out on human gingival fibroblasts showing that the AZ31 and AZ31-PEG plates had good cytocompatibility. Finally, the antibiofilm activity on Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa was carried out by evaluating the capacity of inhibition of biofilm adhesion and formation. The results demonstrated a significant reduction in biofilm formation by Staphylococcus epidermidis on AZ31-QAS.

Evaluation of the Degradation Properties of Plasma Electrolytically Oxidized Mg Alloy AZ31 Using Fluid Dynamic Accelerated Tests for Biodegradable Implants

Magnesium alloys are promising biodegradable implant materials due to their excellent biocompatibility and non-toxicity. However, their poor corrosion resistance limits their application in vivo. Plasma electrolytic oxidation (PEO) is a powerful technique to improve the corrosion resistance of magnesium alloys. In this study, we present the accelerated degradation of PEO-treated AZ31 samples using a fluid dynamic test. The samples were prepared using different concentrations of KOH as an electrolyte along with NaSiO3. The anodizing time and the biasing time were optimized to obtain the increased corrosion resistance. The analysis of the degraded samples using microscopy, SEM EDX measurements, and by calculating mass loss and corrosion rates showed a significant increase in the corrosion resistance after the polymer (Resomer© LG 855 S) coating was applied to the anodized samples. The results confirm (or convince) that PEO treatment is an effective way to improve the corrosion resistance of AZ31 magnesium alloy. The fluid dynamic test can be used as an accelerated degradation test for biodegradable alloys in simulated body fluids at a physiological temperature. The polymer coating further improves the corrosion resistance of the PEO-treated AZ31 samples.

Design and characterization of β-tricalcium phosphate-based self-passivating coatings on magnesium alloys

Background: Magnesium alloys degrade rapidly in salt solutions, which limits their use without passivating treatments. AZ31 alloy is particularly promising for implant applications owing to its biodegradability and mechanical properties, necessitating effective corrosion-resistant coatings. Aim: In this study, a self-passivating reactive coating was designed and evaluated for AZ31 magnesium alloy plates using β-tricalcium phosphate (TCP) to enhance corrosion resistance and biocompatibility. Methods: Solutions of TCP, trisodium citrate, magnesium nitrate, hydroxyethyl cellulose (HEC), and sodium chloride were used to dip-coat AZ31 plates. The coated samples were immersed in 3.5 wt% NaCl solution. Phase evolution was analysed using gravimetry, X-ray diffraction (XRD), energy-dispersive X-ray (EDX) spectroscopy, and scanning electron microscopy (SEM). The biological response of the coated samples was evaluated through MTT and resazurin assays. Results: The coating formed a stable TCP/HEC layer that gradually dissolved over two weeks, converting the surface to magnesium hydroxide, magnesium oxychloride, and magnesium phosphate phases. The formation of brucite, responsible for passivation in the long term, was observed. The coating effectively prevented excessive magnesium oxychloride formation and stabilised magnesium hydroxide after one week. Biological characterization indicated that the coating on AZ31 is safe on the Saos-2 and L929 cell lines. Conclusion: The TCP-based coating enhances the corrosion resistance of AZ31 alloy in salt solutions, promoting passivating phases and limiting corrosive products, thereby ameliorating biocompatibility issues. This coating demonstrates substantial potential for extending the longevity and functionality of magnesium alloy implants.

An overview of magnesium-based implants in orthopaedics and a prospect of its application in spine fusion

Due to matching biomechanical properties and significant biological activity, Mg-based implants present great potential in orthopedic applications. In recent years, the biocompatibility and therapeutic effect of magnesium-based implants have been widely investigated in trauma repair. In contrast, the R&D work of Mg-based implants in spinal fusion is still limited. This review firstly introduced the general background for Mg-based implants. Secondly, the mechanical properties and degradation behaviors of Mg and its traditional and novel alloys were reviewed. Then, different surface modification techniques of Mg-based implants were described. Thirdly, this review comprehensively summarized the biological pathways of Mg degradation to promote bone formation in neuro-musculoskeletal circuit, angiogenesis with H-type vessel formation, osteogenesis with osteoblasts activation and chondrocyte ossification as an integrated system. Fourthly, this review followed the translation process of Mg-based implants via updating the preclinical studies in fracture fixation, sports trauma repair and reconstruction, and bone distraction for large bone defect. Furthermore, the pilot clinical studies were involved to demonstrate the reliable clinical safety and satisfactory bioactive effects of Mg-based implants in bone formation. Finally, this review introduced the background of spine fusion surgeryand the challenges of biological matching cage development. At last, this review prospected the translation potential of a hybrid Mg-PEEK spine fusion cage design.

Surface engineering of pure magnesium in medical implant applications

This review comprehensively surveys the latest advancements in surface modification of pure magnesium (Mg) in recent years, with a focus on various cost-effective procedures, comparative analyses, and assessments of outcomes, addressing the merits and drawbacks of pure Mg and its alloys. Diverse economically feasible methods for surface modification, such as hydrothermal processes and ultrasonic micro-arc oxidation (UMAO), are discussed, emphasizing their exceptional performance in enhancing surface properties. The attention is directed towards the biocompatibility and corrosion resistance of pure Mg, underscoring the remarkable efficacy of techniques such as Ca-deficientca-deficient hydroxyapatite (CDHA)/MgF2 bi-layer coating and UMAO coating in electrochemical processes. These methods open up novel avenues for the application of pure Mg in medical implants. Emphasis is placed on the significance of adhering to the principles of reinforcing the foundation and addressing the source. The advocacy is for a judicious approach to corrosion protection on high-purity Mg surfaces, aiming to optimize the overall mechanical performance. Lastly, a call is made for future in-depth investigations into areas such as composite coatings and the biodegradation mechanisms of pure Mg surfaces, aiming to propel the field towards more sustainable and innovative developments.

Physiomimetic biocompatibility evaluation of directly printed degradable porous iron implants using various cell types

Additively manufactured (AM) degradable porous metallic biomaterials offer unique opportunities for satisfying the design requirements of an ideal bone substitute. Among the currently available biodegradable metals, iron has the highest elastic modulus, meaning that it would benefit the most from porous design. Given the successful preclinical applications of such biomaterials for the treatment of cardiovascular diseases, the moderate compatibility of AM porous iron with osteoblast-like cells, reported in earlier studies, has been surprising. This may be because, as opposed to static in vitro conditions, the biodegradation products of iron in vivo are transported away and excreted. To better mimic the in situ situations of biodegradable biomaterials after implantation, we compared the biodegradation behavior and cytocompatibility of AM porous iron under static conditions to the conditions with dynamic in situ-like fluid flow perfusion in a bioreactor. Furthermore, the compatibility of these scaffolds with four different cell types was evaluated to better understand the implications of these implants for the complex process of natural wound healing. These included endothelial cells, L929 fibroblasts, RAW264.7 macrophage-like cells, and osteoblastic MG-63 cells. The biodegradation rate of the scaffolds was significantly increased in the perfusion bioreactor as compared to static immersion. Under either condition, the compatibility with L929 cells was the best. Moreover, the compatibility with all the cell types was much enhanced under physiomimetic dynamic flow conditions as compared to static biodegradation. Our study highlights the importance of physiomimetic culture conditions and cell type selection when evaluating the cytocompatibility of degradable biomaterials in vitro. STATEMENT OF SIGNIFICANCE: Additively manufactured (AM) degradable porous metals offer unique opportunities for the treatment of large bony defects. Despite the successful preclinical applications of biodegradable iron in the cardiovascular field, the moderate compatibility of AM porous iron with osteoblast-like cells was reported. To better mimic the in vivo condition, we compared the biodegradation behavior and cytocompatibility of AM porous iron under static condition to dynamic perfusion. Furthermore, the compatibility of these scaffolds with various cell types was evaluated to better simulate the process of natural wound healing. Our study suggests that AM porous iron holds great promise for orthopedic applications, while also highlighting the importance of physio-mimetic culture conditions and cell type selection when evaluating the cytocompatibility of degradable biomaterials in vitro.

Novel Phosphate Conversion Coating with Superior Corrosion Resistance on the Mg-Al-RE Alloy Based on the Introduction of Silane

A novel chemical conversion method based on an aqueous electrolyte solution containing hydrolyzed silane as a crucial film-forming agent has been developed successfully. An organic/inorganic composite coating with superior corrosion protection was fabricated on the Mg-Al-RE alloy. The micro-morphology and chemical composition of the coating were examined using scanning electron microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. The prepared conversion coating possesses a double-layer structure, with a dense bottom layer and a loose outer layer containing microcracks. In addition, the anti-corrosion capacity of various samples was evaluated using salt spray, hydrogen evolution, and electrochemical tests. The analysis revealed that the samples converted by 3-aminopropyl triethoxysilane (APTES)-phosphate solution possessed a higher corrosion resistance. Compared to the blank sample, a 2 orders of magnitude reduction in icorr (6.678 × 10-7 A/cm2) and a 1.360 V improvement in Ecorr were observed. The MPCC-Si sample exhibited the lowest hydrogen evolution rate, indicating the best corrosion protection. Also, the rust grade could still reach 7 after 72 h of the neutral salt spray test.

Polymeric Coatings for Magnesium Alloys for Biodegradable Implant Application: A Review

Magnesium (Mg) alloys are a very attractive material of construction for biodegradable temporary implants. However, Mg alloys suffer unacceptably rapid corrosion rates in aqueous environments, including physiological fluid, that may cause premature mechanical failure of the implant. This necessitates a biodegradable surface barrier coating that should delay the corrosion of the implant until the fractured/damaged bone has healed. This review takes a brief account of the merits and demerits of various existing coating methodologies for the mitigation of Mg alloy corrosion. Since among the different coating approaches investigated, no single coating recipe seems to address the degradation control and functionality entirely, this review argues the need for polymer-based and biodegradable composite coatings.

Advances in the Modification of Silane-Based Sol-Gel Coating to Improve the Corrosion Resistance of Magnesium Alloys

As the lightest structural materials, magnesium (Mg) alloys play a significant role in vehicle weight reduction, aerospace, military equipment, energy saving, and emission reduction. However, the poor corrosion resistance of Mg alloys has become a bottleneck restricting its wide application. Developing a good surface protective coating can effectively improve the corrosion resistance of Mg alloys. The silane-based sol-gel coating technology has been widely used in the corrosion protection of Mg alloys in recent years due to its advantages of simple process, accessible tailoring of film composition and structure, and excellent corrosion resistance. Whereas the synthesis of sol-gel coatings includes the hydrolysis and dehydration process, which may inherently contain micron or nano defects in the coatings, thereby making it detrimental to the anti-corrosion effect. Therefore, in order to enhance their protection against corrosion, the appropriate modification of sol-gel coatings has become a current research hotspot. This review is based on the modification methods of silane-based sol-gels on the surface of Mg alloys, which are divided into four categories: bare sol-gel, nanoparticles, corrosion inhibitors, and sol-gel-based composite coatings. The modification methods and corrosion protection mechanism are discussed respectively, and the application, development, and research strategies of silane-based sol-gel coatings are included.

A "built-up" composite film with synergistic functionalities on Mg-2Zn-1Mn bioresorbable stents improves corrosion control effects and biocompatibility

Control of premature corrosion of magnesium (Mg) alloy bioresorbable stents (BRS) is frequently achieved by the addition of rare earth elements. However, limited long-term experience with these elements causes concerns for clinical application and alternative methods of corrosion control are sought after. Herein, we report a "built-up" composite film consisting of a bottom layer of MgF₂ conversion coating, a sandwich layer of a poly (1, 3-trimethylene carbonate) (PTMC) and 3-aminopropyl triethoxysilane (APTES) co-spray coating (PA) and on top a layer of poly (lactic-co-glycolic acid) (PLGA) ultrasonic spray coating to decorate the rare earth element-free Mg-2Zn-1Mn (ZM21) BRS for tailoring both corrosion resistance and biological functions. The developed "built-up" composite film shows synergistic functionalities, allowing the compression and expansion of the coated ZM21 BRS on an angioplasty balloon without cracking or peeling. Of special importance is that the synergistic corrosion control effects of the "built-up" composite film allow for maintaining the mechanical integrity of stents for up to 3 months, where complete biodegradation and no foreign matter residue were observed about half a year after implantation in rabbit iliac arteries. Moreover, the functionalized ZM21 BRS accomplished re-endothelialization within one month.

Heteropolysaccharides in sustainable corrosion inhibition: 4E (Energy, Economy, Ecology, and Effectivity) dimensions

Carbohydrate polymers (polysaccharides) and their derivatives are widely utilized in sustainable corrosion inhibition (SCI) because of their various fascinating properties including multiple adsorption sites, high solubility and high efficiency. Contrary to traditional synthetic polymer-based corrosion inhibitors, polysaccharides are related to the 4E dimension, which stands for Energy, Economy, Ecology, and Effectivity. Furthermore, they are relatively more environmentally benign, biodegradable, and non-bioaccumulative. The current review describes the SCI features of various heteropolysaccharides, including gum Arabic (GA), glycosaminoglycans (chondroitin-4-sulfate (CS), hyaluronic acid (HA), heparin, etc.), pectin, alginates, and agar for the first time. They demonstrate impressive anticorrosive activity for different metals and alloys in a variety of corrosive electrolytes. Through their adsorption at the metal/electrolyte interface, heteropolysaccharides function by producing a corrosion-protective film. In general, their adsorption follows the Langmuir isotherm model. In their molecular structures, heteropolysaccharides contain several polar functional groups like -OH, -NH₂, -COCH₃, -CH₂OH, cyclic and bridging O, -CH₂SO₃H, -SO₃OH, -COOH, -NHCOCH₃, -OHOR, etc. that serve as adsorption centers when they bind to metallic surfaces.

Review: 3-Aminopropyltriethoxysilane (APTES) Deposition Methods on Oxide Surfaces in Solution and Vapor Phases for Biosensing Applications

Surface functionalization and bioreceptor immobilization are critical processes in developing a highly sensitive and selective biosensor. The silanization process with 3-aminopropyltriethoxysilane (APTES) on oxide surfaces is frequently used for surface functionalization because of beneficial characteristics such as its bifunctional nature and low cost. Optimizing the deposition process of the APTES layer to obtain a monolayer is crucial to having a stable surface and effectively immobilizing the bioreceptors, which leads to the improved repeatability and sensitivity of the biosensor. This review provides an overview of APTES deposition methods, categorized into the solution-phase and vapor-phase, and a comprehensive summary and guide for creating stable APTES monolayers on oxide surfaces for biosensing applications. A brief explanation of APTES is introduced, and the APTES deposition methods with their pre/post-treatments and characterization results are discussed. Lastly, APTES deposition methods on nanoparticles used for biosensors are briefly described.

Surface Heparinization of a Magnesium-Based Alloy: A Comparison Study of Aminopropyltriethoxysilane (APTES) and Polyamidoamine (PAMAM) Dendrimers

Magnesium (Mg)-based alloys are biodegradable metallic biomaterials that show promise in minimizing the risks of permanent metallic implants. However, their clinical applications are restricted due to their rapid in vivo degradation and low surface hemocompatibilities. Surface modifications are critically important for controlling the corrosion rates of Mg-based alloys and improving their hemocompatibilities. In the present study, two heparinization methods were developed to simultaneously increase the corrosion resistance and hemocompatibility of the AZ31 Mg alloy. In the first method, the surface of the AZ31 alloy was modified by alkali-heat treatment and then aminolyzed by 3-amino propyltriethoxy silane (APTES), a self-assembly molecule, and heparin was grafted onto the aminolyzed surface. In the second method, before heparinization, polyamidoamine dendrimers (PAMAM4-4) were grafted onto the aminolyzed surface with APTES to increase the number of surface functional groups, and heparinization was subsequently performed. The presence of a peak with a wavelength of about 1560 cm^-1 in the FTIR spectrum for the sample modified with APTES and dendrimers indicated aminolysis of the surface. The results indicated that the corrosion resistance of the Mg alloy was significantly improved as a result of the formation of a passive layer following the alkali-heat treatment. The results obtained from a potentiodynamic polarization (PDP) test showed that the corrosion current in the uncoated sample decreased from 25 µA to 3.7 µA in the alkali-heat-treated sample. The corrosion current density was reduced by 14 and 50 times in samples treated with the self-assembly molecules, APTES and dendrimers, respectively. After heparinization, the clotting time for pristine Mg was greatly improved. Clotting time increased from 480 s for the pristine Mg sample to 630 s for the APTES- and heparin-modified samples and to 715 s for the PAMAM- and heparin-modified samples. Cell culture data showed a slight improvement in the cell-supporting behavior of the modified samples.

Natural Coatings and Surface Modifications on Magnesium Alloys for Biomedical Applications

Magnesium (Mg) alloys have great potential in biomedical applications due to their incomparable properties regarding other metals, such as stainless steels, Co-Cr alloys, and titanium (Ti) alloys. However, when Mg engages with body fluids, its degradation rate increases, inhibiting the complete healing of bone tissue. For this reason, it has been necessary to implement protective coatings to control the rate of degradation. This review focuses on natural biopolymer coatings used on Mg alloys for resorbable biomedical applications, as well as some modification techniques implemented before applying natural polymer coatings to improve their performance. Issues such as improving the corrosion resistance, cell adhesion, proliferation, and biodegradability of natural biopolymers are discussed through their basic comparison with inorganic-type coatings. Emphasis is placed on the expected biological behavior of each natural polymer described, to provide basic information as a reference on this topic.

Biocompatible silane adhesion layer on titanium implants improves angiogenesis and osteogenesis

Silane adhesion layer strategy has been widely used to covalently graft biomolecules to the titanium implant surface, thereby conferring the implant bioactivity to ameliorate osseointegration. However, few researchers pay attention to the effects of silanization parameters on biocompatibility and biofunctionality of the silane adhesion layers. Accordingly, the present study successfully fabricated the silane adhesion layers with different thickness, intactness, and surface morphologies by introducing 3-aminopropyltriethoxysilane on the alkali-treated titanium surface in time-varied processing of silanization. The regulatory effects of the silane adhesion layers on angiogenesis and osteogenesis were assessed in vitro. Results showed that the prolonged silanization processing time increased the thickness and intactness of the silane adhesion layer and significantly improved its biocompatibility. Notably, the silane adhesion layer prepared after 12 h of silanization exhibited a brain-like surface morphology and benefited the adhesion and proliferation of endothelial cells (ECs) and osteoblasts (OBs). Moreover, the layer promoted angiogenesis via stimulating vascular endothelial growth factor (VEGF) secretion and nitric oxide (NO) production of ECs. Simultaneously, it improved osteogenesis by enhancing alkaline phosphatase (ALP) activity, collagen secretion, and extracellular matrix mineralization of OBs. This work systematically investigated the biocompatibility and biofunctionality of the modified silane adhesion layers, thus providing valuable references for their application in covalently grafting biomolecules on the titanium implant surface.

In Vitro Monitoring of Magnesium-Based Implants Degradation by Surface Analysis and Optical Spectroscopy

Magnesium (Mg)-based degradable alloys have attracted substantial attention for tissue engineering applications due to their biodegradability and potential for avoiding secondary removal surgeries. However, insufficient data in the existing literature regarding Mg's corrosion and gas formation after implantation have delayed its wide clinical application. Since the surface properties of degradable materials constantly change after contact with body fluid, monitoring the behaviour of Mg in phantoms or buffer solutions could provide some information about its physicochemical surface changes over time. Through surface analysis and spectroscopic analysis, we aimed to investigate the structural and functional properties of degradable disks. Since bubble formation may lead to inflammation and change pH, monitoring components related to acidosis near the cells is essential. To study the bubble formation in cell culture media, we used a newly developed Mg alloy (based on Mg, zinc, and calcium), pure Mg, and commercially available grade 2 Titanium (Ti) disks in Dulbecco's Modified Eagle Medium (DMEM) solution to observe their behaviour over ten days of immersion. Using surface analysis and the information from near-infrared spectroscopy (NIRS), we concluded on the conditions associated with the medical risks of Mg alloy disintegration. NIRS is used to investigate the degradation behaviour of Mg-based disks in the cell culture media, which is correlated with the surface analysis where possible.

A surface-eroding poly(1,3-trimethylene carbonate) coating for magnesium based cardiovascular stents with stable drug release and improved corrosion resistance

Magnesium alloys with integration of degradability and good mechanical performance are desired for vascular stent application. Drug-eluting coatings may optimize the corrosion profiles of magnesium substrate and reduce the incidence of restenosis simultaneously. In this paper, poly (trimethylene carbonate) (PTMC) with different molecular weight (50,000 g/mol named as PTMC5 and 350,000 g/mol named as PTMC35) was applied as drug-eluting coatings on magnesium alloys. A conventional antiproliferative drug, paclitaxel (PTX), was incorporated in the PTMC coating. The adhesive strength, corrosion behavior, drug release and biocompatibility were investigated. Compared with the PLGA control group, PTMC coating was uniform and gradually degraded from surface to inside, which could provide long-term protection for the magnesium substrate. PTMC35 coated samples exhibited much slower corrosion rate 0.05 μA/cm2 in comparison with 0.11 μA/cm2 and 0.13 μA/cm2 for PLGA and PTMC5 coated counterparts. In addition, PTMC35 coating showed more stable and sustained drug release ability and effectively inhibited the proliferation of human umbilical vein vascular smooth muscle cells. Hemocompatibility test indicated that few platelets were adhered on PTMC5 and PTMC35 coatings. PTMC35 coating, exhibiting surface erosion behavior, stable drug release and good biocompatibility, could be a good candidate as a drug-eluting coating for magnesium-based stent.

Advances in coatings on magnesium alloys for cardiovascular stents - A review

Magnesium (Mg) and its alloys, as potential biodegradable materials, have drawn wide attention in the cardiovascular stent field because of their appropriate mechanical properties and biocompatibility. Nevertheless, the occurrence of thrombosis, inflammation, and restenosis of implanted Mg alloy stents caused by their poor corrosion resistance and insufficient endothelialization restrains their anticipated clinical applications. Numerous surface treatment tactics have mainly striven to modify the Mg alloy for inhibiting its degradation rate and enduing it with biological functionality. This review focuses on highlighting and summarizing the latest research progress in functionalized coatings on Mg alloys for cardiovascular stents over the last decade, regarding preparation strategies for metal oxide, metal hydroxide, inorganic nonmetallic, polymer, and their composite coatings; and the performance of these strategies in regulating degradation behavior and biofunction. Potential research direction is also concisely discussed to help guide biological functionalized strategies and inspire further innovations. It is hoped that this review can give assistance to the surface modification of cardiovascular Mg-based stents and promote future advancements in this emerging research field.

Bioresponsive starPEG-heparin hydrogel coatings on vascular stents for enhanced hemocompatibility

Hydrogel coatings can improve the biocompatibility of medical devices. However, stable surface bonding and homogeneity of hydrogel coatings are often challenging. This study exploits the benefits of biohybrid hydrogels of crosslinked four-armed poly(ethylene glycol) and heparin to enhance the hemocompatibility of cobalt‑chromium (CoCr) vascular stents. A bonding layer of dual silane and poly(ethylene-alt-maleic anhydride) (PEMA) treatment was applied to the stent to provide covalent immobilization and hydrophilicity for the homogeneous spreading of the hydrogel. A spray coating technology was used to distribute the aqueous solution of the reactive hydrogel precursors onto the sub-millimeter struts of the stents, where the solution polymerized to a homogeneous hydrogel film. The coating was mechanically stable on the stent after ethanol dehydration, and the stents could be stored in a dry state. The homogeneity and stability of the coating during stent expansion were verified. Quasistatic and dynamic whole blood incubation experiments showed substantial suppression of the pro-coagulant and inflammatory activity of the bare metal by the coating. Translation of the technology to industrial coating devices and future surface modification of stents with anti-inflammatory hydrogels are discussed.

Sol-gel coating loaded with inhibitor on ZE21B Mg alloy for improving corrosion resistance and endothelialization aiming at potential cardiovascular application

To improve the service performance of vascular stents, we designed/selected a series of organic compounds from commercial drugs, natural plants, and marine life as the potential corrosion inhibitors for ZE21B alloy. Paeonol condensation tyrosine (PCTyr) Schiff base was found to be the most efficient inhibitor among them. The biocompatible, self-healing, anti-corrosive sol-gel coating loaded with corrosion inhibitor was fabricated on the Mg substrate through a convenient dip-coating tactic. The corrosion resistance, self-healing ability, cytotoxicity, and hemocompatibility of the coated sample were evaluated. These results suggested the potentiality of Schiff base inhibitor-loaded sol-gel coating for enhanced corrosion protection and desired biocompatibility of bioabsorbable cardiovascular implants.

Promising Methods for Corrosion Protection of Magnesium Alloys in the Case of Mg-Al, Mg-Mn-Ce and Mg-Zn-Zr: A Recent Progress Review

High specific strength characteristics make magnesium alloys widely demanded in many industrial applications such as aviation, astronautics, military, automotive, bio-medicine, energy, etc. However, the high chemical reactivity of magnesium alloys significantly limits their applicability in aggressive environments. Therefore, the development of effective technologies for corrosion protection is an urgent task to ensure the use of magnesium-containing structures in various fields of application. The present paper is aimed to provide a short review of recent achievements in corrosion protection of magnesium alloys, both surface treatments and coatings, with particular focus on Mg-Al-Mn-Ce, Mg-Al-Zn-Mn and Mg-Zn-Zr alloys, because of their wide application in the transport industry. Recent progress was made during the last decade in the development of protective coatings (metals, ceramics, organic/polymer, both single layers and multilayer systems) fabricated by different deposition techniques such as anodization, physical vapour deposition, laser processes and plasma electrolytic oxidation.

Bioresorption Control and Biological Response of Magnesium Alloy AZ31 Coated with Poly-β-Hydroxybutyrate

Magnesium and its alloys are not normally used as bioresorbable temporary implants due to their high and uncontrolled degradation rate in a physiological liquid environment. The improvement of corrosion resistance to simulated body fluids (SBF) of a magnesium alloy (AZ31) coated with poly-β-hydroxybutyrate (PHB) was investigated. Scanning electron microscopy, Fourier transform infrared spectrometer, and contact angle measurements were used to characterize surface morphology, material composition, and wettability, respectively. pH modification of the SBF corroding medium, mass of Mg2+ ions released, weight loss of the samples exposed to the SBF solution, and electrochemical experiments were used to describe the corrosion process and its kinetics. The material’s biocompatibility was described by evaluating the effect of corrosion by products collected in the SBF equilibrating solution on hemolysis ratio, cytotoxicity, nitric oxide (NO), and total antioxidant capacity (T-AOC). The results showed that the PHB coating can diffusively control the degradation rate of magnesium alloy, improving its biocompatibility: the hemolysis rate of materials was lower than 5%, while in vitro human umbilical vein endothelial cell (HUVEC) compatibility experiments showed that PHB-coated Mg alloy promoted cell proliferation and had no effect on the NO content and that the T-AOC was enhanced compared with the normal group and bare AZ31 alloy. PHB-coated AZ31 magnesium alloy extraction fluids have a less toxic behavior due to the lower concentration of corrosion byproducts deriving from the diffusion control exerted by the PHB coating films both from the metal surface to the solution and vice versa. These findings provide more reference value for the selection of such systems as tunable bioresorbable prosthetic materials.

Tuning of the Mg Alloy AZ31 Anodizing Process for Biodegradable Implants

Coatings were grown on the AZ31 Mg alloy by a hard anodizing process in the hot glycerol phosphate-containing electrolyte. Anodizing conditions were optimized, maximizing corrosion resistance estimated by impedance measurements carried out in Hank's solution at 37 °C. A post anodizing annealing treatment (350 °C for 24 h) allowed us to further enhance the corrosion resistance of the coatings mainly containing magnesium phosphate according to energy-dispersive X-ray spectroscopy and Raman analyses. Gravimetric measurements revealed a hydrogen evolution rate within the limits acceptable for application of AZ31 in biomedical devices. In vitro tests demonstrated that the coatings are biocompatible with a preosteoblast cell line.

Silane coatings modified with hydroxyapatite nanoparticles to enhance the biocompatibility and corrosion resistance of a magnesium alloy

The fast corrosion rate of magnesium alloys has restricted their use as biodegradable implants. Hence developing a practical approach to retard the corrosion rate of the AZ31 magnesium alloy, as well as promoting cell adhesion and proliferation is of great importance. Silane coatings were applied through dip coating, on samples pretreated in hydrofluoric acid. Samples were immersed in simulated body fluid at 37 °C, and the coating performance was assessed by electrochemical impedance spectroscopy. The coating morphologies of samples were investigated through field emission scanning electron microscopy and a cell viability/proliferation (MTT) test was performed to evaluate cellular response. A 2.2 μm-thick coating was accomplished, which increased the corrosion resistance to three orders of magnitude higher than that of the bare sample. Hydroxyapatite nanoparticles were added to the silane coating to improve biocompatibility and facilitate bone formation. Changing the concentration of hydroxyapatite nanoparticles not only helped to optimize the barrier properties of the silane coating but also ameliorated MG-63 osteoblastic cell growth. The findings showed great promise to enhance and maintain the corrosion barrier property and induce high osteoblastic differentiation by employing 1000 mg L⁻¹ of hydroxyapatite nanoparticles.

Incorporation of hydroxyapatite nanoparticles in silane coatings improves both corrosion resistance and cell viability on magnesium AZ31 implants.

Silanized NaCa2HSi3O9 nanorods with a reduced pH increase on Ti for improving osteogenesis and angiogenesis in vitro

NaCa₂HSi₃O₉ nanorods with silane layers allow efficient Ca and Si release and controlled pH increase, and can enhance osteogenesis and angiogenesis on the Ti implant surface.

In vivo study of self-assembled alkylsilane coated degradable magnesium devices

Magnesium (Mg) and its alloys are candidate materials for resorbable implantable devices, such as orthopedic devices or cardiovascular stents. Mg has a number advantages, including mechanical properties, light weight, its osteogenic effects and the fact that its degradation products are nontoxic and naturally present in the body. However, production of H2 gas during the corrosion reaction can cause formation of gas pockets at the implantation site, posing a barrier to clinical applications of Mg. It is therefore desirable to develop methods to control corrosion rate and gas pocket formation around the implants. Here we evaluate the potential of self-assembled multilayer alkylsilane (AS) coatings to control Mg device corrosion and formation of gas pockets in vivo and to assess effects of the AS coatings on the surrounding tissues in a subcutaneous mouse model over a 6 weeks' period. The coating significantly slowed down corrosion and gas pocket formation as evidenced by smaller gas pockets around the AS coated implants (ANOVA; p = 0.013) and decrease in the weight loss values (t test; p = 0.07). Importantly, the microCT and profilometry analyses demonstrated that the coating inhibited the pitting corrosion. Specifically, the roughness of the coated samples was ∼30% lower than uncoated specimen (p = 0.02). Histological assessment of the tissues under the implant revealed no inflammation or foreign body reaction. Overall, our results demonstrate the feasibility of use of the seld assembled AS coatings for reduction of gas pocket formation around the resorbable Mg devices. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 342-351, 2019.

Strategic design of a Mussel-inspired in situ reduced Ag/Au-Nanoparticle Coated Magnesium Alloy for enhanced viability, antibacterial property and decelerated corrosion rates for degradable implant Applications

Magnesium (Mg) and its alloys have attracted much attention as a promising candidate for degradable implant applications however the rapid corrosion of magnesium inside the human body greatly limits its use as an implant material. Therefore, coating the alloy surface with a multifunctional film is a promising way to overcome the drawbacks. Here we propose for the first time a multifunction layer coating to enhance the cell viability, antibacterial property and decelerated corrosion rates to act as a novel material to be used for degradable implant Applications. For that, the magnesium alloy (AZ31) was first treated with hydrofluoric acid (HF) and then dopamine tris Hydrochloric acid (tris-HCL) solution. The reducing catechol groups in the polydopamine (PD) layer subsequently immobilize silver/gold ions in situ to form uniformly dispersed Ag/Au nanoparticles on the coating layer. The successful formation of Ag/Au nanoparticles on the HF-PD AZ31 alloy was confirmed using XPS and XRD, and the morphology of all the coated samples were investigated using SEM images. The alloy with HF-PDA exhibit enhanced cell attachment and proliferation. Moreover, the nanoparticle immobilized HF-PD alloy exhibited dramatic corrosion resistance enhancement with superior antibacterial properties and accountable biocompatibility. Thus the result suggest that HF-PD Ag/Au alloy has great potential in the application of degradable implant and the surface modification method is of great significance to determine its properties.

Magnesium Implants: Prospects and Challenges

Owing to their suitable mechanical property and biocompatibility as well as the technological possibility of controlling their high corrosion rates, magnesium and its alloys have attracted significant attention as temporary bio-implants. Though the ability of magnesium to harmlessly biodegrade and its inherent biocompatibility make magnesium alloys a suitable choice for a temporary implant, their high corrosion rates limit their practical application, as the implants can potentially corrode away even before the healing process has completed. Different approaches, such as alloying, surface modification, and conversion coatings, have been explored to improve the corrosion resistance of various magnesium alloys. However, the corrosion behavior of magnesium implants with and without a surface modification has been generally investigated under in-vitro conditions, and studies under in-vivo conditions are limited, which has contributed to the lack of translation of magnesium implants in practical applications. This paper comprehensively reviews the prospects of magnesium alloy implants and the current challenges due to their rapid degradation in a physiological environment. This paper also provides a comprehensive review of the corrosion mitigation measures for these temporary implants.

Etched Fiber Bragg Grating Biosensor Functionalized with Aptamers for Detection of Thrombin

A biosensor based on an etched Fiber Bragg Grating (EFBG) for thrombin detection is reported. The sensing system is based on a Fiber Bragg Grating (FBG) with a Bragg wavelength of 1550 nm, wet-etched in hydrofluoric acid (HF) for ~27 min, to achieve sensitivity to a refractive index (RI) of 17.4 nm/RIU (refractive index unit). Subsequently, in order to perform a selective detection of thrombin, the EFBG has been functionalized with silane-coupling agent 3-(aminopropyl)triethoxysilane (APTES) and a cross-linker, glutaraldehyde, for the immobilization of thrombin-binding aptamer. The biosensor has been validated for thrombin detection in concentrations ranging from 10 nM to 80 nM. The proposed sensor presents advantages with respect to other sensor configurations, based on plasmonic resonant tilted FBG or Long Period Grating (LPG), for thrombin detection. Firstly, fabricating an EFBG only requires chemical etching. Moreover, the functionalization method used in this study (silanization) allows the avoidance of complicated and expensive fabrications, such as thin film sputtering or chemical vapor deposition. Due to their characteristics, EFBG sensors are easier to multiplex and can be used in vivo. This opens new possibilities for the detection of thrombin in clinical settings.

Effect of High- and Low-Molecular-Weight Hyaluronic-Acid-Functionalized-AZ31 Mg and Ti Alloys on Proliferation and Differentiation of Osteoblast Cells

The quality of patient care has increased dramatically in recent years because of the development of lightweight orthopedic metal implants. The success of these orthopedic implants may be compromised by impaired cytocompatibility and osteointegration. Biomimetic surface engineering of metal implants using biomacromolecules including hyaluronic acid (HA) has been used an effective approach to provide conditions favorable for the growth of bone forming cells. To date, there have been limited studies on osteoblasts functions in response to metal substrates modified with the hyaluronic acid of different molecular weight for orthopedic applications. In this study, we evaluated the osteoblasts functions such as adhesion, proliferation, and differentiation in response to high- and low-molecular-weight HA (denoted as h-HA and l-HA, respectively) functionalized on Ti (h-HA-Ti and l-HA-Ti substrates, respectively) and corrosion-resistant silane coated-AZ31 Mg alloys (h-HA-AZ31 and l-HA-AZ31). The DNA quantification study showed that adhesion and proliferation of osteoblasts were significantly decreased by h-HA immobilized on Ti or AZ31 substrates when compared to low-molecular-weight counterpart over a period of 14 days. On the contrary, h-HA significantly increased the osteogenic differentiation of osteoblast over l-HA, as confirmed by the enhanced expression of ALP, total collagen, and mineralization of extracellular matrix. In particular, the h-HA-AZ31 substrates greatly enhanced the osteoblast differentiation among tested samples (l-HA-AZ31, l-HA-Ti, h-HA-Ti, and Ti alone), which is ascribed to the osteoinductive activity of h-HA, relatively up-regulated intracellular Ca²⁺ ([Ca²⁺]_i) and Mg²⁺ ([Mg²⁺]_i) concentrations as well as the alkalization of the cell culture medium. This study suggesting that HA of appropriate molecular weight can be successfully used to modify the surface of metal implants for orthopedic applications.

Enhanced corrosion resistance and cytocompatibility of biomimetic hyaluronic acid functionalised silane coating on AZ31 Mg alloy for orthopaedic applications

This paper reports the corrosion resistant and cytocompatible properties of the hyaluronic acid-silane coating on AZ31 Mg alloy. In this study, the osteoinductive properties of high molecular weight hyaluronic acid (HA, 1-4 MDa) and the corrosion protection of silane coatings were incorporated as a composite coating on biodegradable AZ31 Mg alloy for orthopaedic applications. The multi-step fabrication of coatings first involved dip coating of a passivated AZ31 Mg alloy with a methyltriethoxysilane-tetraethoxysilane sol-gel to deposit a dense, cross-linked and corrosion resistant silane coating (AZ31-MT). The second step was to create an amine-functionalised surface by treating coated alloy with 3-aminopropyl-triethoxy silane (AZ31-MT-A) which facilitated the immobilisation of HA via EDC-NHS coupling reactions at two different concentrations i.e 1 mg.ml^-1 (AZ31-MT-A-HA1) and 2 mg.ml^-1 (AZ31-MT-A-HA2). These coatings were characterised by Fourier transform infrared spectroscopy, atomic force microscopy and static contact angle measurements which confirmed the successful assembly of the full coatings onto AZ31 Mg alloy. The influence of HA-silane coating on the corrosion of Mg alloy was investigated by electrical impedance spectroscopy and long-term immersion studies measurements in HEPES buffered DMEM. The results showed an enhanced corrosion resistance of HA functionalised silane coated AZ31 substrate over the uncoated equivalent alloy. Furthermore, the cytocompatibility of MC3T3-E1 osteoblasts was evaluated on HA-coated AZ31-MT-A substrates by live-dead staining, quantification of total cellular DNA content, scanning electron microscope and alkaline phosphatase activity. The results showed HA concentration-dependent improvement of osteoblast cellular response in terms of enhanced cell adhesion, proliferation and differentiation. These findings hold great promise in employing such biomimetic multifunctional coatings to improve the corrosion resistance and cytocompatibility of biodegradable Mg-based alloy for orthopaedic applications.

Surface modification of stainless steel for biomedical applications: Revisiting a century-old material

Stainless steel (SS) has been widely used as a material for fabricating cardiovascular stents/valves, orthopedic prosthesis, and other devices and implants used in biomedicine due to its malleability and resistance to corrosion and fatigue. Despite its good mechanical properties, SS (as other metals) lacks biofunctionality. To be successfully used as a biomaterial, SS must be made resistant to the biological environment by increasing its anti-fouling properties, preventing biofilm formation (passive surface modification), and imparting functionality for eluting a specific drug or capturing selected cells (active surface modification); these features depend on the final application. Various physico-chemical techniques, including plasma vapor deposition, electrochemical treatment, and attachment of different linkers that add functional groups, are used to obtain SS with increased corrosion resistance, improved osseointegration capabilities, added hemocompatibility, and enhanced antibacterial properties. Existing literature on this topic is extensive and has not been covered in an integrated way in previous reviews. This review aims to fill this gap, by surveying the literature on SS surface modification methods, as well as modification routes tailored for specific biomedical applications.

STATEMENT OF SIGNIFICANCE

Stainless steel (SS) is widely used in many biomedical applications including bone implants and cardiovascular stents due to its good mechanical properties, biocompatibility and low price. Surface modification allows improving its characteristics without compromising its important bulk properties. SS with improved blood compatibility (blood contacting implants), enhanced ability to resist bacterial infection (long-term devices), better integration with a tissue (bone implants) are examples of successful SS surface modifications. Existing literature on this topic is extensive and has not been covered in an integrated way in previous reviews. This review paper aims to fill this gap, by surveying the literature on SS surface modification methods, as well as to provide guidance for selecting appropriate modification routes tailored for specific biomedical applications.

Silane coatings of metallic biomaterials for biomedical implants: A preliminary review

In response to increased attention in literature, this work provides a qualitative review surrounding the application of silane-based coatings of metallic biomaterials for biomedical implants. Included herein is both a brief summary of existing knowledge and concepts regarding silane-based thin films, along with an analysis of recent peer-reviewed publications and advances towards their practical application for biomedical coatings. Specifically, the review identifies innovative silane-based coatings according to their molecular identity and film structure and analyses their impact on the biocorrosion resistance, protein adsorption, cell viability, and antimicrobial properties of the overall coated implant. It is shown that a range of common silanes clearly exhibit promising properties for biomedical implant coatings, but further work is needed, particularly on mechanisms of physiological interaction and characteristic effects of silane functional groups, before seeing clinical use. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2901-2918, 2018.

Biomimetic Hyaluronic Acid-Lysozyme Composite Coating on AZ31 Mg Alloy with Combined Antibacterial and Osteoinductive Activities

This study presents the covalent grafting of a hyaluronic acid-lysozyme (HA-LZ) composite onto corrosion-resistant silane-coated AZ31 Mg alloy via EDC-NHS coupling reactions. The HA-LZ composite coatings created a smooth and hydrophilic surface with the increased concentration of functional lysozyme complexed to the hyaluronic acid. This was confirmed by the measurement of AFM, water contact angle, and quantification of hyaluronic acid and lysozyme. The colonization of S.aureus on HA-LZ composite-coated substrates was significantly reduced as compared to the hyaluronic acid, lysozyme coated and uncoated AZ31 controls. Such activity is due to the enhanced antibacterial activity of lysozyme component as observed from the spread plate assay, propidium iodide staining, and scanning electron microscopy. Furthermore, morphology of the osteoblast cells, alkaline phosphatase activity and DNA quantification studies demonstrated the improved biocompatibility and osteoinductive properties of HA-LZ-coated substrates. This was verified by comparing with the lysozyme coated and uncoated AZ31 substrates in terms of cell adhesion, proliferation, and differentiation of osteoblastic cells. Therefore, such multifunctional composite coatings with antibacterial and osteoinductive properties are promising can be potentially used for the surface modifications of orthopedic implants.

Hemocompatible ɛ-polylysine-heparin microparticles: A platform for detecting triglycerides in whole blood

Triglycerides are clinically important marker for atherosclerosis, heart disease and hypertension. Here, a platform for detecting triglycerides in whole blood directly was developed based on hemocompatible ɛ-polylysine-heparin microparticles. The obtained products of ɛ-polylysine-heparin microparticles were characterized by fourier transform infrared (FT-IR) spectra, transmission electron microscopy (TEM) and ζ-potential. Moreover, the blood compatibility of ɛ-polylysine-heparin microparticles was characterized by in vitro coagulation tests, hemolysis assay and whole blood adhesion tests. Considering of uniform particle size, good dispersibility and moderate long-term anticoagulation capability of the microparticles, a Lipase-(ɛ-polylysine-heparin)-glassy carbon electrode (GCE) was constructed to detect triglycerides. The proposed biosensor had good electrocatalytic activity towards triglycerides, in which case the sensitivity was 0.40μAmg^-1dLcm^-2 and the detection limit was 4.67mgdL^-1 (S/N = 3). Meanwhile, the Lipase-(ɛ-polylysine-heparin)-GCE electrode had strong anti-interference ability as well as a long shelf-life. Moreover, for the detection of triglycerides in whole blood directly, the detection limit was as low as 5.18mgdL^-1. The new constructed platform is suitable for detecting triglycerides in whole blood directly, which provides new analytical systems for clinical illness diagnosis.

In situ incorporation of heparin/bivalirudin into a phytic acid coating on biodegradable magnesium with improved anticorrosion and biocompatible properties

Drugs were incorporated into a phytic acid coating on Mg by an in situ chemical route for corrosion control and biocompatibility.

A novel biodegradable and biologically functional arginine-based poly(ester urea urethane) coating for Mg–Zn–Y–Nd alloy: enhancement in corrosion resistance and biocompatibility

Novel biodegradable and functional Arg-PEUU coating materials for MgZnYNd alloy stents may make drugs like sirolimus or paclitaxel unnecessary.

Enhanced in Vitro and in Vivo Performance of Mg-Zn-Y-Nd Alloy Achieved with APTES Pretreatment for Drug-Eluting Vascular Stent Application

Bioabsorbable magnesium alloys are becoming prominent as temporary functional implants, as they avoid the risks generated by permanent metallic implants such as persistent inflammation and late restenosis. Nevertheless, the overfast corrosion of Mg alloys under physiological conditions hinders their wider application as medical implant materials. Here we investigate a simple one-step process to introduce a cross-linked 3-amino-propyltrimethoxysilane (APTES) silane physical barrier layer on the surface of Mg-Zn-Y-Nd alloys prior to electrostatic spraying with rapamycin-eluting poly(lactic-co-glycolic acid) (PLGA) layer. Surface microstructure was characterized by scanning electron microscope and Fourier transform infrared spectroscopy. Nanoscratch test verified the superior adhesion strength of PLGA coating in the group pretreated with APTES. Electrochemical tests combined with long-term immersion results suggested that the preferable in vitro anticorrosion behavior could be achieved by dense APTES barrier. Cell morphology and proliferation data demonstrated that APTES pretreated group resulted in remarkably preferable compatibility for both human umbilical vein endothelial cells and vascular smooth muscle cells. On the basis of excellent in vitro mechenical property, the animal study on the APTES pretreated Mg-Zn-Y-Nd stent implanted into porcine coronary arteries confirmed benign tissue compatibility as well as re-endothelialization without thrombogenesis or in-stent restenosis at six-month followup.

In Vitro Corrosion and Cytocompatibility of a Microarc Oxidation Coating and Poly(L-lactic acid) Composite Coating on Mg-1Li-1Ca Alloy for Orthopedic Implants

Manipulating the degradation rate of biomedical magnesium alloys poses a challenge. The characteristics of a microarc oxidation (MAO), prepared in phytic acid, and poly(L-lactic acid) (PLLA) composite coating, fabricated on a novel Mg-1Li-1Ca alloy, were studied through field emission scanning electron microscopy (FE-SEM), electron probe X-ray microanalysis (EPMA), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The corrosion behaviors of the samples were evaluated via hydrogen evolution, potentiodynamic polarization and electrochemical impedance spectroscopy in Hanks' solution. The results indicated that the MAO/PLLA composite coatings significantly enhanced the corrosion resistance of the Mg-1Li-1Ca alloy. MTT and ALP assays using MC3T3 osteoblasts indicated that the MAO/PLLA coatings greatly improved the cytocompatibility, and the morphology of the cells cultured on different samples exhibited good adhesion. Hemolysis tests showed that the composite coatings endowed the Mg-1Li-1Ca alloys with a low hemolysis ratio. The increased solution pH resulting from the corrosion of magnesium could be tailored by the degradation of PLLA. The degradation mechanism of the composite coatings was discussed. The MAO/PLLA composite coating may be appropriate for applications on degradable Mg-based orthopedic implants.

Fabrication and corrosion resistance properties of super-hydrophobic coatings on iron and steel substrates by creating micro-/nano-structures and modifying rough surfaces

Super-hydrophobic surfaces are usually prepared by manipulating the surface roughness and surface chemistry of various materials.

Corrosion resistance of layer-by-layer assembled polyvinylpyrrolidone/polyacrylic acid and amorphous silica films on AZ31 magnesium alloys

A layer-by-layer (LbL)-assembled composite coating containing SiO₂ and a biocompatible polyvinylpyrrolidone (PVP) and polyacrylic acid (PAA) multi-layer, designated as SiO₂/(PVP/PAA)₅, was prepared on AZ31 Mg alloy via dip-coating.

Enhanced corrosion protection and biocompatibility of a PLGA–silane coating on AZ31 Mg alloy for orthopaedic applications

This paper reports a multi-step procedure to fabricate a novel corrosion resistant and biocompatible PLGA–silane coating on the magnesium (Mg) alloy AZ31.