pH Stimuli-Responsive, Rapidly Self-healable Coatings Enhanced the Corrosion Resistance and Osteogenic Differentiation of Mg-1Ca Osteoimplant.

Mg-Ca alloys have emerged as a promising research direction for biomedical implants in the orthopedic field. However, their clinical use is deterred by their fast corrosion rate. In this work, a pH stimuli-responsive silk-halloysite (HNT)/phytic acid (PA) self-healing coating (Silk-HNT/PA) is constructed to slow down the corrosion rate of Mg-1Ca alloy and its cell viability and osteogenic differentiation ability are enhanced. The Silk-HNT/PA coating exhibits appealing active corrosion protection, by eliciting pH-triggerable self-healing effects, while simultaneously affording superior biocompatibility and osteogenic differentiation ability. Moreover, in vivo studies by histological analysis also demonstrate better osseointegration for the Silk-HNT/PA coated Mg-1Ca alloy. In summary, the Silk-HNT/PA coating in the present study has great potential in enhancing the biomedical utility of Mg alloys.

Tailoring ZE21B Alloy with Nature-Inspired Extracellular Matrix Secreted by Micro-Patterned Smooth Muscle Cells and Endothelial Cells to Promote Surface Biocompatibility.

Delayed surface endothelialization is a bottleneck that restricts the further application of cardiovascular stents. It has been reported that the nature-inspired extracellular matrix (ECM) secreted by the hyaluronic acid (HA) micro-patterned smooth muscle cells (SMC) and endothelial cells (EC) can significantly promote surface endothelialization. However, this ECM coating obtained by decellularized method (dECM) is difficult to obtain directly on the surface of degradable magnesium (Mg) alloy. In this study, the method of obtaining bionic dECM by micro-patterning SMC/EC was further improved, and the nature-inspired ECM was prepared onto the Mg-Zn-Y-Nd (ZE21B) alloy surface by self-assembly. The results showed that the ECM coating not only improved surface endothelialization of ZE21B alloy, but also presented better blood compatibility, anti-hyperplasia, and anti-inflammation functions. The innovation and significance of the study is to overcome the disadvantage of traditional dECM coating and further expand the application of dECM coating to the surface of degradable materials and materials with different shapes.

Investigation of Mg-xLi-Zn alloys for potential application of biodegradable bone implant materials.

Implant therapy after osteosarcoma surgery is a major clinical challenge currently, especially the requirements for mechanical properties, degradability of the implants, and their inhibition of residual tumor cells. Biodegradable magnesium (Mg) alloy as medical bone implant material has full advantages and huge potential development space. Wherein, Mg-lithium (Li) based alloy, as an ultra-light alloy, has good properties for implants under certain conditions, and both Mg and Li have inhibitory effects on tumor cells. Therefore, Mg-Li alloy is expected to be applied in bone implant materials for mechanical supporting and inhibiting tumor cells simultaneously. In this contribution, the Mg-xLi-Zinc (Zn) series alloys (x = 3 wt%, 6 wt%, 9 wt%) were prepared to study the influence of different elements and contents on the structure and properties of the alloy, and the biosafety of the alloy was also evaluated. Our data showed that the yield strength, tensile strength, and elongation of as-cast Mg-xLi-Zn alloy were higher than those of as-cast Mg-Zn alloy; Mg-xLi-Zn alloy can kill osteosarcoma cells (MG-63) in a concentration-dependent manner, wherein Mg-3Li-Zn alloy (x = 3 wt%) and Mg-6Li-Zn alloy (x = 6 wt%) promoted the proliferation of osteoblasts (MC3T3) at a certain concentration of Li. In summary, our study demonstrated that the Mg-6Li-Zn alloy could be potentially applied as a material of orthopedic implant for its excellent multi-functions.

A DFT study of the adsorption of short peptides on Mg and Mg-based alloy surfaces.

Adsorption of short peptides, including three dipeptides: arginine-glycine (Arg-Gly), glycine-aspartic acid (Gly-Asp), arginine-aspartic acid (Arg-Asp), and one tripeptide arginine-glycine-aspartic acid (RGD), on the surfaces of Mg and Mg alloys (Mg-Zn, Mg-Y, and Mg-Nd), was studied using the first-principles calculations based on density functional theory (DFT), considering van der Waals (vdW) correction. The calculated adsorption energies (Eads) of short peptides on the clean Mg(0001) surface are in the range of -1.73 to -2.80 eV per dipeptide, and -3.24 eV for RGD. The short peptides prefer to bond to Mg atoms at the surface by the O and N anions in their functional groups. For the clean Mg(0001) surface, the Eads of the short peptides are exclusively dominated by the number of functional groups binding to the surface. However, for the surface of the Mg-Zn alloy (1% Zn), the adsorption of the peptides is clearly enhanced (by about 0.3 eV per peptide) due to the enhanced N-Mg bond and the electrostatic interactions between the doped Zn at the surface and the backbone chains of the peptides. Furthermore, the attractive interactions are increased with the increase of doped Zn contents (up to 3%). In contrast, for the surfaces of Mg-Y (1% Y) and Mg-Nd (1% Nd) alloys, the adsorption of the peptides is slightly weakened compared to that on the clean Mg(0001) surfaces. Our results provide useful guidance in understanding the interactions between peptides and the Mg-based biomedical alloy surfaces at the atomic scale in the biomimetic coating fields.

Investigation on the in vitro cytocompatibility of Mg-Zn-Y-Nd-Zr alloys as degradable orthopaedic implant materials.

Mg-Zn-Y-Nd-Zr alloy has been developed as a new type of biodegradable orthopaedic implant material by the authors' research group with its excellent mechanical properties and controllable degradation rate. In this study, the cytocompatibility of Mg-Zn-Y-Nd-Zr alloy was systematically evaluated through in vitro cell culture method. MTT assay was applied to evaluate the cytotoxicity of Mg-Zn-Y-Nd-Zr alloy and no toxic effect was observed on L929 and MC3T3-E1 cells followed the protocol of ISO 10993 standard. Considering the potential ion accumulation in the bony environment, this study further investigated the cytotoxic effect of accumulated metallic ions during the alloy degradation by extending the extract preparation time. When the extract preparation time was prolonged to 1440 h, the accumulated metallic ions leaded to severe cell apoptosis, of which the combined ion concentration was determined as 39.5-65.8 µM of Mg2+, 3.5-5.9 µM of Zn2+, 0.44-0.74 µM of Y3+, 0.3-0.52 µM of Nd3+ and 0.11-0.18 µM of Zr4+ for L929, and 65.8-92.2 µM of Mg2+, 5.9-8.3 µM of Zn2+, 0.74-1.04 µM of Y3+, 0.52-0.73 µM of Nd3+ and 0.18-0.25 µM of Zr4+ for MC3T3-E1 cells. Besides the cell viability assessment, high expression of ALP activity and calcified nodules implied that metal elements in Mg-Zn-Y-Nd-Zr alloys can promote the osteogenic differentiation. Hence, excellent cytocompatibility has equipped Mg-Zn-Y-Nd-Zr alloy as a promising candidate for orthopaedic implant application, which can remarkably guide the magnesium-based alloy design and provide scientific evidence for clinical practice in future.

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.

A Cu(â ¡)-eluting coating through silk fibroin film on ZE21B alloy designed for in situ endotheliazation biofunction.

In the cardiovascular field, coating containing copper used to catalyze NO (nitric oxide) production on non-degradable metal surfaces have shown unparalleled expected performance, but there are few studies on biodegradable metal surfaces. Magnesium-based biodegradable metals have been applied in cardiovascular field in large-scale because of their excellent properties. In this study, the coating of copper loaded in silk fibroin is fabricated on biodegradable ZE21B alloy. Importantly, the different content of copper is set to investigate the effects of on the degradation performance and cell behavior of magnesium alloy. Through electrochemical and immersion experiments, it is found that high content of copper will accelerate the corrosion of magnesium alloy. The reason is the spontaneous micro-batteries between copper and magnesium with the different standard electrode potentials, that is, the galvanic corrosion accelerates the corrosion of magnesium alloy. Moreover, the coating formed through silk fibroin by the right amount copper not only have a protective effect on the ZE21B alloy substrate, but also promotes the adhesion and proliferation of endothelial cells in blood vessel micro-environment. The production of NO catalyzed by copper ions makes this trend more significant, and inhibits the excessive proliferation of smooth muscle cells. These findings can provide guidance for the amount of copper in the coating on the surface of biodegradable magnesium alloy used for cardiovascular stent purpose.

Co-immobilization of natural marine polysaccharides and bioactive peptides on ZE21B magnesium alloy to enhance hemocompatibility and cytocompatibility.

Degradable magnesium alloy stents are considered to be ideal candidates to replace the traditional non-degradable stents for the treatment of cardiovascular diseases. However, bare magnesium alloy stents usually degrade too fast and show poor hemocompatibility and cytocompatibility, which seriously affects their clinical use. In this study, surface modification based on the MgF2 layer, polydopamine (PDA) coating, fucoidan and CAG peptides was performed on the Mg-Zn-Y-Nd (ZE21B) magnesium alloy with the purpose of improving its corrosion resistance, hemocompatibility and cytocompatibility for vascular stent application. After modification, the ZE21B alloy showed better corrosion resistance. Moreover, the lower hemolysis rate, platelet adhesion and activation, and fibrinogen adsorption and denaturation proved the improved hemocompatibility of modified ZE21B alloy in in vitro blood experiments. Furthermore, the co-immobilization of fucoidan and CAG peptides significantly promoted the adhesion, proliferation, migration and NO release of endothelial cells (ECs) on the modified ZE21B alloy, and meanwhile the modification with fucoidan and CAG peptides inhibited the adhesion and proliferation of smooth muscle cells (SMCs) and suppressed the expression of proinflammatory factors in the macrophages (MAs). The surface modification obviously enhanced the corrosion resistance, hemocompatibility and cytocompatibility of ZE21B alloy, and provided an effective strategy for the development of degradable vascular stents.

The enhanced antibacterial effect of BNNS_Van@CS/MAO coating on Mg alloy for orthopedic applications.

The development of multifunctional Mg-based active implants with controllable degradation and antibacterial capabilities has become a hotspot in the research field of biodegradable metallic materials. To this end, a BN nanosheets (BNNS) _vancomycin (Van) @chitosan (CS) nanocomposite coating containing two antibacterial components (BNNS and Van) was prepared on Mg alloys via a micro-arc oxidation (MAO) pre-treatment combined with following electrodeposition. The related characterizations of the coating show that the composite coating has a high roughness, hydrophobicity and fair corrosion resistance. In vitro antibacterial experiments show that the BNNS_Van@CS/MAO composite coating have obvious inhibitory effect on the growth of both E. coli and S. aureus. The antibacterial effect of the BNNS_Van@CS/MAO composite coating was attributed to the synergistic effect of CS, BNNS and Van. This study provides a valuable surface modification strategy for developing multifunctional Mg-based implants with good corrosion resistance and antibacterial properties.

Surface modification of biodegradable magnesium alloy with poly (L-lactic acid) and sulfonated hyaluronic acid nanoparticles for cardiovascular application.

Magnesium (Mg) and its alloys have attracted extensive attention of researchers in the field of cardiovascular implants due to their good mechanical properties and biosafety. Constructing a multifunctional hybrid coating seems to be an effective strategy to address the insufficient endothelialization and poor corrosion resistance of Mg alloy vascular stents. In this study, a dense layer of magnesium fluoride (MgF2) was prepared on the surface of Mg alloy aiming at better corrosion resistance; Thereafter, sulfonated hyaluronic acid (S-HA) was made into small sized nanoparticles (NP) which were deposited on the MgF2 surface by self-assembly method, followed with poly-L-lactic acid (PLLA) coating preparation by one-step pulling method. The blood and cell tests showed that the composite coating had good blood compatibility, pro-endothelial, anti-hyperplasia and anti-inflammatory functions. Compared to current clinical PLLA@ Rapamycin coating, our PLLA/NP@S-HA coating showed better functions of promoting endothelial cells growth. These results strongly furnished a promising and feasible strategy for the surface modification of Mg-based degradable cardiovascular stents.

A biodegradable magnesium alloy vascular stent structure: Design, optimisation and evaluation.

The existing biodegradable magnesium alloy stent (BMgS) structure is prone to problems, such as insufficient support capacity and early fracture at areas of concentrated stress. Herein, a stent structural design, which reduced the cross section of the traditional sin-wave stent by nearly 30% and introduces a regular arc structure in the middle of the support ring. The influence of the dual-parameter design of bending radius (r) and ring length (L) on plastic deformation, expansion and compression resistance performances are discussed. The non-dominated sorting genetic algorithm II (NSGA-II) was used to search for the optimal solution. It was found that the introduction of parameter r effectively improved the plastic deformation and expansion performance, and the reduction of L improved stent compression resistance. Finally, an optimized stent configuration was obtained. In vitro mechanical tests, including balloon inflation, radial strength and flexibility, verified the simulation results. The radial strength for the optimised stent increases by approximately 40% compared with that for the sinusoidal stent. Microarea X-ray diffraction result shows that the circumferential residual stress for the optimised stent decreases by half compared with that for the sinusoidal stent, thus effectively reducing the stress concentration phenomenon. STATEMENT OF SIGNIFICANCE: Despite current progress in BMgS research, the optimal design of the structure is limited. We present a new type of structurally designed stent. The performance of this stent was analysed by a finite element method and experimentally verified. The structural design positively influenced stent performance.

Recent advances on the mechanical behavior of zinc based biodegradable metals focusing on the strain softening phenomenon.

Zinc based biodegradable metals (BMs) show great potential to be used in various biomedical applications, owing to their superior biodegradability and biocompatibility. Some high-strength (ultimate tensile strength > 600 MPa) Zn based BMs have already been developed through alloying and plastic working, making their use in load-bearing environments becomes a reality. However, different from Mg and Fe based BMs, Zn based BMs exhibit significant "strain-softening" effect that leads to limited uniform deformation. Non-uniform deformation is detrimental to Zn based devices or implants, which will possibly lead to unexpected failure. People might be misled by the considerable fracture elongation of Zn based BMs. Thus, it is important to specify uniform elongation as a term of mechanical requirements for Zn based BMs. In this review, recent advances on the mechanical properties of Zn based BMs have been comprehensively summarized, especially focusing on the strain softening phenomenon. At first, the origin and evaluation criteria of strain softening were introduced. Secondly, the effects of alloying elements (including element type, single or multiple addition, and alloying content) and microstructural characteristics (grain size, constituent phase, phase distribution, etc.) on mechanical properties (especially for uniform elongation) of Zn based BMs were summarized. Finally, how to get a good balance between strength and uniform elongation was generally discussed based on the service environment. In addition, possible ways to minimize or eliminate the strain softening effect were also proposed, such as controlling of twins, solute clusters, and grain boundary characteristics. All these items above would be helpful to understand the mechanical instability of Zn based BMs, and to make the full usage of them in the future medical device design. STATEMENT OF SIGNIFICANCE: Biodegradable metals (BMs) is a hotspot in the field of metallic biomaterials. Fracture elongation is normally adopted to quantify the deformability of Mg and Fe based BMs owing to their negligible necking strain, yet the strain softening would occur in Zn based BMs, which is extremely detrimental to performance of their medical device. In this review paper, a better understanding the mechanical performance of Zn-based BMs with the term "uniform elongation" instead of "fracture elongation" was depicted, and possible ways to minimize or eliminate the strain softening effect were also proposed, such as twins, solute clusters, self-stable dislocation network, and grain boundary characteristics. It would be helpful to understand the mechanical instability of Zn based BMs and making full usage of it in the future medical device design.

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.

Application of 3D Printing Technology in Bone Tissue Engineering: A Review.

Clinically, the treatment of bone defects remains a significant challenge, as it requires autogenous bone grafts or bone graft substitutes. However, the existing biomaterials often fail to meet the clinical requirements in terms of structural support, bone induction, and controllable biodegradability. In the treatment of bone defects, 3D porous scaffolds have attracted much attention in the orthopedic field. In terms of appearance and microstructure, complex bone scaffolds created by 3D printing technology are similar to human bone. On this basis, the combination of active substances, including cells and growth factors, is more conducive to bone tissue reconstruction, which is of great significance for the personalized treatment of bone defects. With the continuous development of 3D printing technology, it has been widely used in bone defect repair as well as diagnosis and rehabilitation, creating an emerging industry with excellent market potential. Meanwhile, the diverse combination of 3D printing technology with multi-disciplinary fields, such as tissue engineering, digital medicine, and materials science, has made 3D printing products with good biocompatibility, excellent osteoinductive capacity, and stable mechanical properties. In the clinical application of the repair of bone defects, various biological materials and 3D printing methods have emerged to make patient-specific bioactive scaffolds. The microstructure of 3D printed scaffolds can meet the complex needs of bone defect repair and support the personalized treatment of patients. Some of the new materials and technologies that emerged from the 3D printing industry's advent in the past decade successfully translated into clinical practice. In this article, we first introduced the development and application of different types of materials that were used in 3D bioprinting, including metal, ceramic materials, polymer materials, composite materials, and cell tissue. The combined application of 3D bioprinting and other manufacturing methods used for bone tissue engineering are also discussed in this article. Finally, we discussed the bottleneck of 3D bioprinting technique and forecasted its research orientation and prospect.

Influence of the second phase on protein adsorption on biodegradable Mg alloys' surfaces: Comparative experimental and molecular dynamics simulation studies.

The effect of the second phase on the mechanical properties and corrosion resistance of Mg alloys has been systematically studied. However, there is limited information on the effect of the second phase on protein adsorption behavior. In the present study, the effect of the second phase on protein adsorption on the surfaces of biodegradable Mg alloys was investigated using experimental methods and molecular dynamics (MD) simulations. The experimental results showed that the effect of the second phase on fibrinogen adsorption was type-dependent. Fibrinogen preferentially adsorbed on Y-, Ce-, or Nd-involved second phases, while the second phase containing Zn inhibited its adsorption. MD simulations revealed the mechanism of the second phase that influenced protein adsorption in terms of charge distribution, surface-protein interaction energy, and water molecule distribution. Our studies proposed a deep understanding of the design of Mg-based biomaterials with superior biocompatibility. STATEMENT OF SIGNIFICANCE: Mechanical properties, uniform degradation, and biocompatibility must be considered while designing biomedical Mg alloys. To improve the mechanical properties and corrosion resistance of Mg alloys, the second phase is usually required. However, the effects of the second phase on biocompatibility of Mg alloys have been rarely reported. Here, the influence of the second phase on protein adsorption was experimentally studied by designing Mg alloys with different types of second phase. The first principle calculation and MD simulation were used to reveal the mechanism by which the second phase influences protein adsorption. This work could be used to better elucidate the protein adsorption mechanisms and design principles to improve the biocompatibility of Mg alloys.

Microstructure and corrosion properties of as sub-rapid solidification Mg-Zn-Y-Nd alloy in dynamic simulated body fluid for vascular stent application.

Magnesium alloy stent has been employed in animal and clinical experiment in recent years. It has been verified to be biocompatible and degradable due to corrosion after being implanted into blood vessel. Mg-Y-Gd-Nd alloy is usually used to construct an absorbable magnesium alloy stent. However, the corrosion resistant of as cast Mg-Y-Gd-Nd alloy is poor relatively and the control of corrosion rate is difficult. Aiming at the requirement of endovascular stent in clinic, a new biomedical Mg-Zn-Y-Nd alloy with low Zn and Y content (Zn/Y atom ratio 6) was designed, which exists quasicrystals to improve its corrosion resistance. Additionally, sub-rapid solidification processing was applied for preparation of corrosion-resisting Mg-Zn-Y-Nd and Mg-Y-Gd-Nd alloys. Compared with the as cast sample, the corrosion behavior of alloys in dynamic simulated body fluid (SBF) (the speed of body fluid: 16 ml/800 ml min(-1)) was investigated. The results show that as sub-rapid solidification Mg-Zn-Y-Nd alloy has the better corrosion resistance in dynamic SBF due to grain refinement and fine dispersion distribution of the quasicrystals and intermetallic compounds in alpha-Mg matrix. In the as cast sample, both Mg-Zn-Y-Nd and Mg-Y-Gd-Nd alloys exhibit poor corrosion resistance. Mg-Zn-Y-Nd alloy by sub-rapid solidification processing provides excellent corrosion resistance in dynamic SBF, which open a new window for biomedical materials design, especially for vascular stent application.

Conjugating heparin, Arg-Glu-Asp-Val peptide, and anti-CD34 to the silanic Mg-Zn-Y-Nd alloy for better endothelialization.

Magnesium alloy is generally accepted as a potential cardiovascular stent material due to its good mechanical properties, biocompatibility, and biodegradability, and has become one of the research hotspots in this field. However, too fast degradation rate and delayed surface endothelialization have been the bottleneck of further application of magnesium alloy stent. In this study, we selected Mg-Zn-Y-Nd, a kind of biodegradable magnesium alloy for cardiovascular stent, and passivated its surface by alkali heat treatment and silane treatment to improve the corrosion resistance, subsequently conjugated Arg-Glu-Asp-Val (REDV) peptide and anti-CD34 to promote endothelial cells adhesion and capture endothelial progenitor cells respectively, further improving surface endothelialization. In addition, the heparin was also immobilized to the Mg-Zn-Y-Nd surface for the consideration of anti-coagulation and anti-inflammation. Systematic material characterization and biological evaluation show that we have successfully developed this composite surface on Mg-Zn-Y-Nd alloy, and achieved multiple functions such as corrosion resistance, promoting endothelialization, and inhibiting platelet/macrophage adhesion.

Preparing a novel magnesium-doped hyaluronan/polyethyleneimine nanoparticle to improve endothelial functionalisation.

Nowadays, tissue engineering vascularisation has become an important means of organ repair and treatment of major traumatic diseases. Vascular endothelial layer regeneration and endothelial functionalisation are prerequisites and important components of tissue engineering vascularisation. The present researches of endothelial functionalisation mainly focus on tissue engineering scaffold preparation and implant surface modification. Few studies have reported the interaction of endothelial functionalisation and scaled materials, especially the nanomaterials. Magnesium (Mg), as an essential cytotropic active element in the human body, should promote the growth of endothelial cells. However, the authors' previous work found that the Mg in the alloys had a defect of delayed endothelialisation, which may be attributed to the non-uniform scales of the degradation products from Mg alloys. To validate this hypothesis and fabricate a novel nanomaterial for tissue engineering vascularisation, the authors prepared Mg-doped hyaluronan (HA)/polyethyleneimine (PEI) nanoparticles for endothelial cells testing. Their data showed that the Mg-doped HA/PEI nanoparticle with small scales (diameter <150 nm) presented better ability on improving endothelial cells growth, functionalisation and nitric oxide release.

Enhancing biocompatibility and corrosion resistance of biodegradable Mg-Zn-Y-Nd alloy by preparing PDA/HA coating for potential application of cardiovascular biomaterials.

In this paper the poly-dopamine (PDA)/hyaluronic acid (HA) coatings with different HA molecular weight (MW, 4 × 103, 1 × 105, 5 × 105 and 1 × 106 Da) were prepared onto the NaOH passivated Mg-Zn-Y-Nd alloy aiming at potential application of cardiovascular implants. The characterization of weight loss, polarization curves and surface morphology indicated that the coatings with HA MW of 1 × 105 (PDA/HA-2) and 1 × 106 Da (PDA/HA-4) significantly enhanced the corrosion resistance of Mg-Zn-Y-Nd. In vitro biological test also suggested better hemocompatibility, pro-endothelialization, anti-hyperplasia and anti-inflammation functions of the PDA/HA-2- and PDA/HA-4-coated Mg-Zn-Y-Nd alloy. Nevertheless, the in vivo implantation of SD rats' celiac artery demonstrated that the PDA/HA-2 had preferable corrosion resistance and biocompatibility.

Tailoring of cardiovascular stent material surface by immobilizing exosomes for better pro-endothelialization function.

Stent intervention as available method in clinic has been widely applied for cardiovascular disease treatment for decades. However, the restenosis caused by late thrombosis and hyperplasia still limits the stents long-term application, and the essential cause is usually recognized as endothelial functionalization insufficiency of the stent material surface. Here, we address this limitation by developing a pro-endothelial-functionalization surface that immobilized a natural factors-loaded nanoparticle, exosome, onto the poly-dopamine (PDA) coated materials via electrostatic binding. This PDA/Exosome surface not only increased the endothelial cells number on the materials, but also improved their endothelial function, including platelet endothelial cell adhesion molecule-1 (CD31) expression, cell migration and nitric oxide release. The pro-inflammation macrophage (M1 phenotype) attachment and synthetic smooth muscle cell proliferation as the interference factors for the endothelialization were not only inhibited by the PDA/Exosome coating, while the cells were also regulated to anti-inflammation macrophage (M2 phenotype) and contractile smooth muscle cell, which may contribute to endothelialization. Thus, it can be summarized this method has potential application on surface modification of cardiovascular biomaterials.