Article

Improved biocompatibility and degradation behavior of biodegradable Zn-1Mg by grafting zwitterionic phosphorylcholine chitosan (PCCs) coating on silane pre-modified surface

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Abstract

With the purpose of regulating corrosion behavior and improving the biocompatibility of Zn-1Mg alloy, we developed a phosphorylcholine chitosan (PCCs) coating forming a bionic cell membrane surface, using a silane conversion layer (APTEs) as the connection layer. Atomic force microscopy (AFM), contact angle (CA), and nano-scratch tests were conducted to study the surface roughness, the hydrophilicity and the adhesion strength of the PCCs layer. Bonding details were investigated by X-ray photoelectron spectroscopy (XPS) and Fourier Transform infrared spectroscopy (FTIR). Electrochemical impedance spectroscopy (EIS) tests were performed in simulated body fluid (SBF) at 37°C to understand the degradation behavior in vitro. The experimental results demonstrated that the PCCs coating remarkably increased resistance against corrosion attack, with approximately 2 order higher value of the film resistance (Rf) than that of the substrate. Simultaneously, the PCCs-modified surface exhibited improved blood compatibility, anti-platelet adhesion, and significantly enhanced cyto-compatibility for human vascular endothelium cells (HUVECs). These results relates to the decreased release of Zn²⁺ and the considerably enhanced surface hydrophilicity. PCCs coated Zn alloys presented in this work are indeed showing the promise for future application in biodegradable vascular stent.

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... However, Mg corrodes too rapidly in vivo and produces a large amount of hydrogen gas beneath the skin, limiting their wide applications [13]. To deal with this problem, surface modification with PCL is implemented to decrease the initial degradation rate of biodegradable Mg, along with other biocompatible and antibacterial elements such as CS and zinc oxide, so that it will not corrode away before the bone tissue is entirely healed [14,15]. PCL is a non-toxic and biodegradable polyester prepared via ring-opening polymerization of the cyclic monomer ε-caprolactone and could be an effective barrier to inhibit the infiltration of the corrosive solution to Mg substrate and further protect the substrate [16]. ...
... CS is a polysaccharide deacetylated from chitin and can be obtained from the exoskeletons of marine crustaceans, shellfish, and some fungi [18,19]. The CS properties, including biocompatibility in the human body, antioxidant activity, antimicrobial activity, hypoallergenic property, and anti-inflammatory activity, have attracted considerable attention in commercial applications [14,18]. In recent years, ZnO, particularly in the form of nanoparticles, has received attention as an antibacterial agent against bacterial infections. ...
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Magnesium has been recognized as a groundbreaking biodegradable biomaterial for implant applications, but its use is limited because it degrades too quickly in physiological solutions. This paper describes the research on the influence of polycaprolactone (PCL)/chitosan (CS)/zinc oxide (ZnO) composite coating (PCL/CS/ZnO) on the corrosion resistance and antibacterial activity of magnesium. The PCL/CS film presented a porous structure with thickness of about 40–50 μm, while after incorporation of ZnO into the PCL/CS, a homogenous film without pores and defects was attained. The ZnO embedded in PCL/CS enhanced corrosion resistance by preventing corrosive ions diffusion in the magnesium substrate. The corrosion, antibacterial, and cell interaction mechanism of the PCL/CS/ZnO composite coating is discussed in this study. In vitro cell culture revealed that the PCL/CS coating with low loaded ZnO significantly improved cytocompatibility, but coatings with high loaded ZnO were able to induce some cytotoxicity osteoblastic cells. It was also found that enhanced antibacterial activity of the PCL/CS/ZnO coating against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria, while less significant antibacterial activity was detected for uncoated Mg and PCL/CS coating. Based on the results, the PCL/CS coatings loaded with low ZnO content may be recommended as a candidate material for biodegradable Mg-based orthopedic implant applications.
... In recent years, a myriad of coatings, ranged from inorganic to organic and composite/hybrid types, have been explored to surface-modify Zn biometals [12,13]. For instance, the inorganic ones include metal oxides/hydroxides (like zirconia oxide (ZrO 2 ), zinc oxide (ZnO), and zinc hydroxide (Zn(OH) 2 )) [12,14,15], phosphates (zinc phosphate (ZnP), strontium phosphate (SrP), and calcium phosphate coatings (CaP)) [15][16][17][18][19]. Organic ones include collagen (Col) [16], polydopamine (PDA) [20], and phosphorylcholine chitosan [21], among others. For composite/hybrid ones, examples are collagen-intermixed CaP or Zn 2 SiO 4 nanorods and bisphosphonate/amino acid/protein-incorporated ZnP [20,[22][23][24], and others. ...
Article
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Osteoporotic (OP) fractures remain a tough clinical challenge owing to their impaired healing outcome, which requires novel biomaterials with osteogenicity for effective healing. Metallic zinc (Zn) is attracting increasing attention for biodegradable intramedullary nails (IMNs) for OP fracture healing thanks to their comprehensive mechanical properties, biosafety, and bioactivity. However, the multiple biofunctions required for OP fracture healing have not been fully met by Zn. Herein, a zoledronate (ZA)-mediated calcium-zinc silicate (Ca(Zn)Si) metal-organic/inorganic hybrid coating was fabricated on Zn-based IMN by coordination chemistry driven via interactions between ZA and Ca2+/Zn2+ as well as in-situ directional growth of Ca(Zn)Si phase. The ZA&Ca(Zn)Si hybrid coating exhibited a homogeneous micro/nanostructure with a granular morphology, which prevented premature fracture failure of IMN in rat femur by ameliorating corrosion mode and decreasing degradation rate of the Zn matrix. More importantly, this hybrid coating enabled sustained release of Zn2+/Ca2+/Si4+ and ZA in the long term, achieving a remarkable effect on vascularized bone regeneration. The coated IMN enhanced angiogenesis–osteogenesis coupling through autocrine and paracrine effects between endothelial cells and bone marrow mesenchymal stem cells. Osteoclastogenesis was repressed by Zn2+ and ZA. This approach offers a new strategy for surface-engineering of biodegradable metals for bone fracture healing.
... The role of polymer coatings is similar to that of inorganic coatings, primarily controlling the release rate of zinc ions and enhancing the biocompatibility of the alloy. For example, researchers have used amphiphilic polymers as coatings on zinc-magnesium alloys, significantly improving the corrosion resistance of the alloy [121]. Other researchers have utilized poly(p-xylene) as a coating to enhance the corrosion resistance of stents. ...
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Objectives To examine the 16-year developmental history, research hotspots, and emerging trends of zinc-based biodegradable metallic materials from the perspective of structural and temporal dynamics. Methods The literature on zinc-based biodegradable metallic materials in WoSCC was searched. Historical characteristics, the evolution of active topics and development trends in the field of zinc-based biodegradable metallic materials were analyzed using the bibliometric tools CiteSpace and HistCite. Results Over the past 16 years, the field of zinc-based biodegradable metal materials has remained in a hotspot stage, with extensive scientific collaboration. In addition, there are 45 subject categories and 51 keywords in different research periods, and 80 papers experience citation bursts. Keyword clustering anchored 3 emerging research subfields, namely, #1 plastic deformation #4 additive manufacturing #5 surface modification. The keyword alluvial map shows that the longest-lasting research concepts in the field are mechanical property, microstructure, corrosion behavior, etc., and emerging keywords are additive manufacturing, surface modification, dynamic recrystallization, etc. The most recent research on reference clustering has six subfields. Namely, #0 microstructure, #2 sem, #3 additive manufacturing, #4 laser powder bed fusion, #5 implant, and #7 Zn–1Mg. Conclusion The results of the bibliometric study provide the current status and trends of research on zinc-based biodegradable metallic materials, which can help researchers identify hot spots and explore new research directions in the field.
... Phosphates such as zinc- [13,17], magnesium- [18], and calcium- [11,19] phosphate conversion layer, and metal oxides such as zinc- [13] and zirconium- [20] oxide are typical examples of the inorganic coating. Organic coatings, such as poly (γ-glutamic acid)-g-dopamine/copper (γ-PGA-g-DA/Cu) [21], Poly (lactic-co-glycolic acid) (PLGA) [22], phosphorylcholine chitosan (PCCs) [23], have been explored on Zn-based metals for biodegradable implants applications. Additionally, some hybrid coatings, such as collagen-zinc/calcium phosphate [12], bioactive molecules (cysteine, phenylalanine, bovine serum albumin, or bisphosphonate) incorporated zinc phosphate (ZnP) of metal-organic/inorganic hybrid coatings [24,25], endothelium-mimicking hybrid coating out of polycarbonate, tannic acid, and copper ions [26], and extracellular matrix-like Zn 2 SiO 4 nanorods layered with collagen I (Col-I) hybrid have been investigated for Zn-based BMs [27], to name just a few. ...
Article
Zn and its alloys are receiving increasing interest for biodegradable orthopedic implant applications owing to their moderate corrosion rate and the potential functionality of Zn2+. However, their non-uniform corrosion behavior and insufficient osteogenic, anti-inflammatory, and antibacterial properties do not meet the comprehensive requirements of orthopedic implants in clinical use. Herein, an aspirin (an acetylsalicylic acid, ASA, 10, 50, 100, and 500 mg/L)-loaded carboxymethyl chitosan (CMC)/gelatin (Gel)-Zn2+ organometallic hydrogel composite coating (CMC/Gel&Zn2+/ASA) was fabricated on a Zn surface via an alternating dip-coating method, aiming to obtain a material with these comprehensive properties improved. The organometallic hydrogel composite coatings, ca. 12-16 μm in thickness, showed compact, homogeneous, and micro-bulge structured surface morphology. The coatings protected well the Zn substrate from pitting/localized corrosion and contained the release of the bioactive components, Zn2+ and ASA, in a sustained and stable manner in long-term in vitro immersions in Hank's solution. The coated Zn showed greater ability to promote proliferation and osteogenic differentiation for MC3T3-E1 osteoblasts, and better anti-inflammatory capacity when compared with uncoated Zn. Additionally, this coating displayed excellent antibacterial activity against both Escherichia coli (>99 % antibacterial rate) and Staphylococcus aureus (>98 % antibacterial rate). Such appealing properties can be attributed to the compositional nature of the coating, namely the sustained release of Zn2+ and ASA, as well as the surface physiochemical properties because of its unique microstructure. This organometallic hydrogel composite coating can be considered a promising option for the surface modification of biodegradable Zn-based orthopedic implants among others.
... However, how to improve the biocompatibility of Zn-Mg alloy stents is an urgent problem. Xie et al. 25 developed a biomimetic phosphorylcholine-chitosan (PCCs) coating (Fig. 4). They modified a layer of 3-aminopropyltriethoxysilane on the metal substrate, then performed a Schiff base reaction on the surface to introduce aldehyde groups, and finally reacted it with phosphorylcholinechitosan to get biomimetic PCCs coating. ...
Article
Medical devices are becoming more and more significant in our daily life. For implantable medical devices, good biocompatibility is required for further use in vivo. Thus, surface modification of medical devices is really important, which gives a wide application scene for a silane coupling agent. The silane coupling agent is able to form a durable bond between organic and inorganic materials. The dehydration process provides linking sites to achieve condensation of two hydroxyl groups. The forming covalent bond brings excellent mechanical properties among different surfaces. Indeed, the silane coupling agent is a popular component in surface modification. Metals, proteins, and hydrogels are using silane coupling agent to link parts commonly. The mild reaction environment also brings advantages for the spread of the silane coupling agent. In this review, we summarize two main methods of using the silane coupling agent. One is acting as a crosslinker mixed in the whole system, and the other is to provide a bridge between different surfaces. Moreover, we introduce their applications in biomedical devices.
... The cells were able to attach and proliferate on this protein layer mimic coating. Sheng et al. [72] anchored a biomimetic phosphorylcholine chitosan coating on the Zne1Mg surface by using a silane conversion layer. They reported the promising effects of the zwitterionic polymer coatings in the aspects of biodegradation and biocompatibility of Zn alloy. ...
Article
Zinc (Zn) has emerged as a promising biodegradable metal with moderate degradation profile and good biocompatibility. The wider application of biodegradable Zn in clinics relies on further optimization of its biodegradation behavior, biological activity, and other functions. In recent years, various surface modification strategies have been applied to biodegradable Zn in the orthopedics and cardiovascular fields, with significant progress made in cytocompatibility, osteogenesis, antibacterial performance, and degradation control. In this review, we summarized various surface modification techniques as well as their formation features for biodegradable Zn. Meanwhile, we proposed combining the surface modification strategy with porous and complex structured Zn alloy. We also discussed the effects of different coatings on the degrading behavior and biocompatibility of the Zn alloys. While most surface modifications attempt to improve the degradation resistance of Zn, plasma electrolytic oxidation and mechanical methods, in particular, can increase the degradation rate of Zn alloys, shortening the implantation period under specific degradation requirements. An ideal surface modification should slow down Zn degradation at the beginning, while speeding it up after the healing process. Regarding biological properties, the biocompatibility, osteointegration, and antibacterial properties of biodegradable Zn have been enhanced through surface modifications. It can be envisioned that, with proper surface design, biodegradation adaptive and biocompatibility adaptive Zn alloys hold great potential for many biomedical applications.
... The currently reported sustained-release strategy for loading drugs or active biomolecules is mainly covalent grafting [4][5][6][7][8][9], which has high grafting efficiency and can achieve a long-term, controllable, and targeted release of loading. However, chemical grafting greatly affects the biological activity of functional compounds, making it difficult to achieve its expected functions [10,11]. ...
Article
Through electrostatic and H-bonding interaction, polyelectrolyte could be self-assembled onto the medical devices via layer-by-layer (LBL) method. However, the built-in instability of LBL coating has seriously limited its further application. The polyphenols were incorporated into the polyelectrolyte coating, which provided various synergistic forces, including electrostatic, H-bonding, π-π stacking, and weak chemical cross-linking. The surface engineering of polyphenol-based sandwich-like films with polyethyleneimine and heparin via LBL self-assembly. This design improved the loading capacity and long-term release of drugs, such as heparin, rapamycin, and gentamicin sulfate. These experiments suggested enhanced durability of antithrombotic potential (over 90 days), good anti-inflammatory and anti-bacteria performances, and promotion of vascular healing. Therefore, all-in-one sandwich-like coatings might be a straightforward, versatile, and durable surface modification method for implantable medical devices.
... The aggregated and activated platelets can promote blood coagulation and even induce thrombus formation. Therefore, the materials with good blood compatibility should have the ability to maintain the normal physiological state of the platelets (Sheng et al., 2020). In this study, platelet adhesion and activation were first applied to investigate the blood compatibility of the modified titanium samples. ...
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Zinc ions (Zn²⁺) are a highly potent bioactive factor with a broad spectrum of physiological functions. In situ continuous and controllable release of Zn²⁺ from the biomaterials can effectively improve the biocompatibility and antibacterial activity. In the present study, inspired by the adhesion and protein cross-linking in the mussel byssus, with the aim of improving the biocompatibility of titanium, a cost-effective one-step metal–catecholamine assembly strategy was developed to prepare a biomimetic dopamine–Zn²⁺ (DA-Zn²⁺) coating by immersing the titanium oxide nanotube (TNT) arrays on the titanium surface prepared by anodic oxidation into an aqueous solution containing dopamine (DA) and zinc ions (Zn²⁺). The DA-Zn²⁺ coatings with the different zinc contents exhibited excellent hydrophilicity. Due to the continuous release of zinc ions from the DA-Zn²⁺ coating, the coated titanium oxide nanotubes displayed excellent hemocompatibility characterized by platelet adhesion and activation and hemolysis assay. Moreover, the DA-Zn²⁺-coated samples exhibited an excellent ability to enhance endothelial cell (EC) adhesion and proliferation. In addition, the DA-Zn²⁺ coating can also enhance the antibacterial activity of the nanotubes. Therefore, long-term in situ Zn²⁺-releasing coating of the present study could serve as the bio-surfaces for long-term prevention of thrombosis, improvement of cytocompatibility to endothelial cells, and antibacterial activity. Due to the easy operation and strong binding ability of the polydopamine on various complicated shapes, the method of the present study can be further applied to other blood contact biomaterials or implantable medical devices to improve the biocompatibility.
... Therefore, PDA can be selected to load FA [23]. The preparation of functional coatings by surface treatment is a common method by which to enhance the comprehensive properties of Mg alloys, such as anodic oxidation [8,24], fluorination [25], phosphate treatment [26], electro-grafting [27,28], silylation [29][30][31], and alkali heat treatment [19,20,32]. Among them, alkali heat treatment has the characteristics of having a simple method, being easy to prepare, having a low cost, and a degradable coating, which is convenient for the next coating preparation and conducive to cell adhesion [19]. ...
Article
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Magnesium (Mg) alloy has been used for medical vascular stents because of its good biocompatibility and degradability, but its rapid degradation and poor blood compatibility limits its further application. In this study, ferulic acid (FA) was conjugated onto the polydopamine (PDA) deposited Mg-Zn-Y-Nd alloy to prepare a PDA/FA multi-functional coating with better corrosion resistance and blood compatibility. The results suggest that the PDA/FA coating possessed potential application for surface modification of a medical Mg alloy.
... The peaks at 101.8, 102.3, and 102.8 eV in Fig. 5e were assigned to Si-C, Si-O-Si, and Si-O-C groups, respectively. It suggested that the dehydration condensation between APTES (Si-OH) and -OH (TBC and chitosan) of the PCBH bead were chemical cross-linked during the heating and polymerization process (Sheng et al., 2020). Moreover, it demonstrated that double cross-linked DCBA bead was successfully prepared. ...
Article
This work prepared a double-cross-linked biohybrid aerogel (DCBA) bead biosorbent from waste bamboo paper and chitosan by sequential physical (hydrogen bonding and electrostatic interaction between -COO⁻ and -NH3⁺ groups) and chemical (polymerization reaction between -COOH and -NH2, dehydration condensation between Si-OH and -OH) cross-linkings. The resulting DCBA bead was applied to remove cationic (Methylene blue, MB) and anionic (Congo red, CR) dyes in single and binary systems. The MB and CR adsorption capacities of DCBA bead increased with increasing adsorbent dosage, contact time, temperature and initial dye concentration. With increasing solution pH, the MB adsorption capacity increased, while that for CR increased first and then decreased. The maximal adsorption capacities for MB and CR were 653.3 and 559.6 mg/g, respectively, in single system. The thermodynamic analysis results showed a spontaneous and endothermic adsorption process. DCBA bead had a good stability and reusability with the removal efficiencies of 49.4 and 60.6% for MB and CR, respectively, after five cycles of adsorption-desorption. In binary system, the adsorption of MB was inhibited by CR, while the removal of CR was enhanced by MB.
... Then, we improved the biocompatibility of implanted medical magnesium alloy materials through the introduction of peptides without damaging the corrosion resistance ( Figure 1). For further reactions, we performed an alkali treatment [14] with enrichment of Mg(OH) 2 in the surface of magnesium and 3-aminopropyl triethoxysilane (APTES) amino pretreatment [15] to graft the silane coupling agent. APTES hydrolysis led to silanol (-Si(OH) 3 ) generation, and the -Si(OH) 3 group in hydrolysed APTES reacted with the -OH group on the Mg surface. ...
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Abstract Magnesium (Mg) and its alloys can be used as biomedical materials because of their excellent mechanical properties and biocompatibility. However, the rapid degradation rate of Mg‐based materials limits their application in biodegradable intravascular stents. To overcome this issue, we constructed a hydrophobic coating on magnesium. After pre‐treatments with alkali and a silane coupling agent of pure magnesium, 4,4’‐diphenylmethane‐diisocyanate (MDI) and amino‐terminated polydimethylsiloxane (H2N–PDMS–NH2) were stepwise deposited on the surface, forming an amino‐containing hydrophobic coating (–(M/P)3) to enhance the corrosion resistance. Furthermore, polypeptide TK14 was immobilised on the hydrophobic coating to promote vascular endothelial cell adhesion and proliferation. The electrochemical results revealed that the self‐corrosion current density (icorr) of –(M/P)3 decreased by approximately 4.5 orders of magnitude compared with that of pure Mg. After TK14 immobilisation, the number of endothelial cells adhering to the surface of –(M/P)3–T increased significantly. Although the corrosion resistance of –(M/P)3–T was slightly reduced, the subcutaneous implantation inflammatory response of the surrounding tissues was lower, showing suitable biocompatibility. Therefore, the polypeptide TK14 functionalised hydrophobic coating may be a promising candidate material for the interface of magnesium‐based cardiovascular implants.
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Till now, the novel Zn-based alloys have attracted extensive attention, due to the excessive dissolution rate in the Mg-based alloys and the detrimental products in the Fe-based biomaterials. In this study, the novel degradable Zn-1 Mg-0.25Nd-xSn alloys were fabricated, and the microstructure, degradation and film formation mechanism were investigated through scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron probe micro-analyzer (EPMA), atomic force microscopy (AFM), confocal laser scanning microscopy (3D/CLSM) and X-ray photoelectron spectroscopy (XPS). The results indicated that the morphology of interdendritic β-lamellar and primary η-Zn obviously changed as the Sn contents increased, whilst the corrosion initiates as a consequence of relative Volta potential differences between the Zn-rich and micro-eutectic phases. Therein, the optimalizing corrosion rate was obtained in the Zn-1 Mg-0.25Nd-0.3Sn, which was associated with the formation of insoluble Zn5(OH)8Cl2, Zn3(PO4)2, Sn(OH)2/Sn(OH)4, reducing the reaction activities of the Zn matrix. Besides, the REs-rich products incorporated into the passive layer and absorbed OH⁻, forming a uniform and dense degradation layer. However, as the Sn contents further increased, the formation of abundant micro-galvanic nucleation sites facilitates the metastable pits dissolution and the probability of transition from metastable to stable.
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Recently emerged metallic zinc (Zn) is a new generation of promising candidates for bioresorbable medical implants thanks to its essential physiological relevance, mechanical strength, and more matched degradation pace to that of tissue healing. Zn‐based metals exhibit excellent biocompatibility in various animal models. However, direct culture of cells on Zn metals yields surprisingly low viability, indicating high cytotoxicity of Zn. This contradicting phenomenon should result from the different degradation mechanisms between in vitro and in vivo. To solve this puzzle, the roles of all major players, i.e., zinc phosphate (ZnP), zinc oxide (ZnO), zinc hydroxide (Zn(OH)2), pH, and Zn2+, which are involved in the degradation process are examined. Data shows that ZnP, not ZnO or Zn(OH)2, significantly enhances its biocompatibility. The mild pH change during degradation also has no significant impact on cell viability. Collectively, ZnP appears to be the key to controlling the biocompatibility of Zn implants and could be applied as a novel surface coating to improve biocompatibility of different implants. Spontaneously formed interfacial zinc phosphate (ZnP), instead of zinc oxide (ZnO) or zinc hydroxide (Zn(OH)2), is the key to controlling the biocompatibility of Zn‐based metals. The ZnO–Zn(OH)2 layer shows a high cytotoxicity while the dense and uniform ZnP interfacial layer enhances biocompatibility and promotes tissue integration.
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The combination of biodegradable metals and additive manufacturing (AM) leads to a revolutionary change of metal implants in many aspects including materials, design, manufacturing, and clinical applications. The AM of nondegradable metals such as titanium and CoCr alloys has proven to be a tremendous success in clinical applications. The AM of biodegradable metals including magnesium (Mg), iron (Fe), and zinc (Zn) is still in its infancy, although much progress has been made in the research field. Element loss and porosity are common processing problems for AM of biodegradable metals like Zn and Mg, which are mainly caused by evaporation during melting under a high-energy beam. The resulting formation quality and properties are closely related to material, design, and processing, making AM of biodegradable metals a typical interdisciplinary subject involving biomaterials, mechanical engineering, and medicine. This work reviews the state of research and future perspective on AM of biodegradable metals from extensive viewpoints such as material, processing, formation quality, design, microstructure, and properties. Effects of powder properties and processing parameters on formation quality are characterized in detail. The microstructure and metallurgical defects encountered in the AM parts are described. Mechanical and biodegradable properties of AM samples are introduced. Design principles and potential applications of biodegradable metal implants produced by AM are discussed. Finally, current research status is summarized together with some proposed future perspectives for advancing knowledge about AM of biodegradable metals. STATEMENT OF SIGNIFICANCE: Rapid development of research and applications on biodegradable metals and additive manufacturing (AM) has been made in recent years. Customized geometric shapes of medical metals with porous structure can be realized accurately and efficiently by laser powder bed fusion (L-PBF), which is beneficial to achieve reliable stress conduction and balanced properties. This review introduces the development history and current status of AM of biodegradable metals and then critically surveys L-PBF of Mg-, Fe-, and Zn-based metals from multiple viewpoints including materials, processing, formation quality, structural design, microstructure, and mechanical and biological properties. The present findings are summarized together with some proposed future challenges for advancing AM of biodegradable metals into real clinical applications.
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Hemocompatibility of blood-contacting biomaterials is one of the most important criteria for their successful in vivo applicability. Thus, extensive in vitro analyses according to ISO 10993-4 are required prior to clinical applications. In this review, we summarize essential aspects regarding the evaluation of the hemocompatibility of biomaterials and the required in vitro analyses for determining the blood compatibility. Static, agitated, or shear flow models are used to perform hemocompatibility studies. Before and after the incubation of the test material with fresh human blood, hemolysis, cell counts, and the activation of platelets, leukocytes, coagulation and complement system are analyzed. Furthermore, the surface of biomaterials are evaluated concerning attachment of blood cells, adsorption of proteins, and generation of thrombus and fibrin networks.
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The primary reactions occurring upon the insertion of Zn-derived materials inside an organism are of the utmost importance as the chemical species resulting from degradation of these new resorbable biomaterials will be crucial for the interaction with the surrounding tissues. In this sense, the degradation of Zn–Mg alloys under physiologically simulated conditions was investigated. The presence of magnesium (1–2%) as an alloying element in Zn alloys affected the composition of the corrosion layer and the associated in vitro degradation behaviour. A detailed physico-chemical characterization of the in vitro built-up of the corrosion layers of pure Zn and two Zn–Mg alloys (Zn–1Mg and Zn–2Mg) was achieved by confocal Raman spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. This study revealed that the presence of Mg in Zn–Mg alloys modulated simonkolleite turnover, promoted brucite formation and yielded a calcium phosphate layer containing skorpionite and hydroxyapatite. These last compounds, by being bone analogues may favour the osseointegration of Zn–Mg-based materials over that of pure Zn. When comparing both Zn–Mg alloys, the distinct evolutions observed in these compounds' (skorpionite and hydroxyapatite) formation may present specific advantageous according to the bone-healing process required. A detailed analysis of the corrosion behaviour, achieved by electrochemical techniques, showed that Zn–Mg alloys had a corrosion resistance inferior to that of pure Zn; however, the built-up of potential biocompatible corrosion layers together with superior strength and castability of these Zn–Mg alloys make them special attractive biomaterials for clinical bone implants, particularly adequate in load-bearing applications.
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Bioabsorbable metal zinc (Zn) is a promising new generation of implantable scaffold for cardiovascular and orthopedic applications. In cardiovascular stent applications, zinc ion (Zn2+) will be gradually released into the surrounding vascular tissues from such Zn-containing scaffolds after implantation. However, the interactions between vascular cells and Zn2+ are still largely unknown. We explored the short-term effects of extracellular Zn2+ on human smooth muscle cells (SMCs) up to 24 h, and an interesting biphasic effect of Zn2+ was observed. Lower concentrations (<80 μM) of Zn2+ had no adverse effects on cell viability but promoted cell adhesion, cell spreading, cell proliferation, cell migration, and enhanced the expression of F-actin and vinculin. Cells treated with such lower concentrations of Zn2+ displayed an elongated shape compared to controls without any treatment. In contrast, cells treated with higher Zn2+ concentrations (80–120 μM) had opposite cellular responses and behaviors. Gene expression profiles revealed that the most affected functional genes were related to angiogenesis, inflammation, cell adhesion, vessel tone, and platelet aggregation. Results indicated that Zn has interesting concentration-dependent biphasic effects on SMCs with low concentrations being beneficial to cellular functions.
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Biodegradable metals have attracted considerable attentions in recent years. Besides the early launched biodegradable Mg and Fe metals, Zn, an essential element with osteogenic potential of human body, is regarded and studied as a new kind of potential biodegradable metal quite recently. Unfortunately, pure Zn is soft, brittle and has low mechanical strength in the practice, which needs further improvement in order to meet the clinical requirements. On the other hand, the widely used industrial Zn-based alloys usually contain biotoxic elements (for instance, ZA series contain toxic Al elements up to 40â €‰wt.%), which subsequently bring up biosafety concerns. In the present work, novel Zn-1X binary alloys, with the addition of nutrition elements Mg, Ca and Sr were designed (cast, rolled and extruded Zn-1Mg, Zn-1Ca and Zn-1Sr). Their microstructure and mechanical property, degradation and in vitro and in vivo biocompatibility were studied systematically. The results demonstrated that the Zn-1X (Mg, Ca and Sr) alloys have profoundly modified the mechanical properties and biocompatibility of pure Zn. Zn-1X (Mg, Ca and Sr) alloys showed great potential for use in a new generation of biodegradable implants, opening up a new avenue in the area of biodegradable metals.
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Sulfanilic acid azocromotrop (SAC) modified reduced graphene oxide (SAC-RGO) was prepared through a simple non-covalent functionalization of graphene oxide (GO) followed by post reduction using hydrazine monohydrate. Spectral analysis (Fourier transform infrared, Raman and X-ray photoelectron spectroscopy) revealed the successful modification of graphene oxide with SAC through π-π interaction. The electrical conductivity of SAC-RGO was found to be ~ 551 S m-1. The capacitive performance of SAC-RGO was recorded in a three electrode set up using 1 (M) aqueous H2SO4 as electrolyte. The -SO3H functionalities of SAC contributed pseducapacitance as evidenced from the redox peaks (at ~ 0.43 and 0.27 V) appeared in the cyclic voltammetric (CV) curves of SAC-RGO. The contribution of electrical double layer capacitance was evidenced from the near rectangular shape CV curves and resulted a high specific capacitance of 366 F g-1 at a current density of 1.2 A g-1 for SAC-RGO electrode. An asymmetric device (SAC-RGO//RGO) was designed with SAC-RGO as positive electrode and RGO as negative electrode. The device showed an energy density of ~25.8 W h Kg-1 at a power density of ~980 W Kg-1. The asymmetric device showed retention in specific capacitance of ~72% after 5000 charge-discharge cycles. The Nyquist data of the device was fitted with Z-View and different components (solution resistance, charge-transfer resistance and Warburg elements) were calculated from the fitted curves.
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The electrochemical behavior of Zn in 0.5 M NaOH solutions containing various concentrations (0.01–0.1 M) of ClO3− or ClO4− anions was studied with potentiodynamic anodic polarization and chronoamperometry techniques. Microstructural and topographical characterization of the pitted surfaces was carried out by ex situ scanning electron microscopy and atomic force microscopy examinations. Addition of either ClO3− or ClO4− stimulated general corrosion and ruptured the passive layer (stable pitting), with ClO3− being more aggressive than ClO4−. Metastable pitting events appear as current oscillations (spikes) at potentials close to the pitting potential when Cl− ions are produced by cathodic reduction of ClO3− and ClO4− before passive layer growth. Current–time measurements are performed at fixed potential after production of Cl− ions and show that the rate of metastable pitting and the intensity of current spikes increase with the potential and the concentration of aggressive anions. Concepts of thin film growth are applied to the passive layer formation in order to explain those results. Metastable events are related to the presence of defects in the passive layer because their frequency and intensity are enhanced in conditions that favor defect formation and roughening in growing films, while stable pitting typically occurs at regions of high metal disorder.
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Heparin (HEP) and phosphorylcholine groups (PC) were grafted onto the polyurethane (PU) surface in order to improve biocompatibility and anticoagulant activity. After the surface grafting sites of PU were amplified with the primary amine groups of polyethylenimine (PEI), heparin was covalently linked onto the surface by the reaction between the amino group and the carboxyl group. PC groups were covalently immobilized on the PU-PEI surface through the reaction between the amino group and the aldehyde group of phosphorylcholine glyceraldehyde (PCGA). The surface density of primary amine groups was determined by a ninhydrin assay. The amino group density reached a maximum of 0.88 μmol/cm2 upon incorporation of 10 wt% PEI. The amount of heparin covalently immobilized on the PU-PEI surface was determined by the toluidine blue method. The grafting chemistry resulted in the comparatively dense immobilization of HEP (2.6 μg/cm2) and PC to the PU-PEI surfaces. The HEP and PC modified surfaces were characterized by water uptake (PU 0.15 mg/cm2, PU-PEI 3.54 mg/cm2, PU-HEP 2.04 mg/cm2, PU-PC 2.38 mg/cm2), water contact angle (PU 95.3°, PU-PEI 34.0°, PU-HEP 39.5°, PU-PC 37.2°), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and scanning electron microscope (SEM). The results demonstrated that the PUPEI surface was successfully grafted with HEP and PC. The hydrophilicity and hemocompatibility of these grafted surfaces were significantly improved. These results suggested that the PU-HEP and PU-PC composite films are promising candidates for blood contacting tissue engineering.
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A novel layer by layer (LbL) assembled structure with phosphorylcholine groups was fabricated to improve the hemocompatibility of paclitaxel/chitosan (PTX/CS) nanofibers (NF) coatings The random copolymers with phosphorylcholine groups poly (2‑methacryloyloxy-ethylphosphorylcholine‑co‑methacrylicacid) (PMAs) were synthesized through free radical polymerization and then first PMA layer formed on PTX/CS NF coatings via electrostatic interactions. After that CS polycation and PMA polyanion thin films LbL formed on PTX/CS NF coatings. The LbL structure was confirmed by X-ray photoelectron spectroscopy (XPS) and water contact angle. The drug release in vitro indicated that the PMA modified PTX/CS NF coatings (PTX/CS-PMA NF coatings) showed a sustained slower release of PTX drug. The LbL coatings containing phosphorylcholine groups could significantly reduce proteins adsorption, platelets adhesion and cell adhesion. They showed a lower platelet (about 6%) and protein (30–40%) (bovine serum albumin, BSA; bovine plasma fibrinogen, Fg) adhesion. Meanwhile, the adhesion of human umbilical vein endothelial cells (HUVECs) was also found reduced. These results demonstrate that the preparation of PMA modified coatings is a simple strategy to improve the hemocompatibility of PTX/CS NF coatings, has good potential for application in blood-contacting materials and devices. Statement of significance We develop a simple method to improve the hemocompatibility of paclitaxel/chitosan (PTX/CS) nanofibers (NF) coatings, which can significantly reduce the protein adsorption, and the adhesion of cells and platelets. Using layer by layer (LbL) assembly with PMA polyanion and CS polycation, multilayered PMA/CS films formed on the PTX/CS NF coatings. The X-ray photoelectron spectroscopy (XPS) and water contact angle characterization demonstrated that a cell outer membrane mimetic structure was formed on the PTX/CS NF coatings. The hemocompatibility of modified surface was significantly improved as shown by 94% adhesion suppression for platelets and 60–70% adsorption suppression for bovine plasma fibrinogen (Fg) and bovine serum albumin (BSA). The drug release in vitro indicated that the PMA modified PTX/CS NF (PTX/CS-PMA) coatings had a sustained drug release. Thus this paper provides a facile method for fabricating cell outer membrane mimetic structure which can improve hemocompatibility of blood-contacting material surfaces.
Article
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.
Article
Compared to magnesium (Mg) or iron (Fe) based biodegradable alloys, Zinc (Zn) alloys exhibit moderate degradation rates, thus regarded as promising implant materials for orthopedic and cardiovascular applications. However, Zn ²⁺ released from degradation process may result certain degrees of cytotoxicity. Thus it is necessary to modify the surface of biodegradable Zn alloys for better biocompatibility. In this paper, a porous ceramic coating was successfully prepared on a Zn-1Mg alloy using plasma electrolytic oxidation (PEO). The effect of the PEO coating on the corrosion resistance and in vitro cyto-compatibility of the Zn-1Mg alloy were evaluated. It was noted that the thickness of the PEO coatings could be adjusted from 6.7 ± 0.5 µm to 28.6 ± 2 µm by increasing the oxidation time from 30 s to 120 s. Longer oxidation time led to a more rough and hydrophobic surface, which was consisted of ZnO and Zn 2 SiO 4 . The stable and protective oxide layer enhanced the corrosion resistance of the Zn-1Mg alloy. The PEO coated Zn-1Mg exhibited better blood compatibility and cyto-compatibility. Decreased hemolytic ratio and lower platelet adhesion was observed on the PEO coated Zn-1Mg sample. The enhanced cyto-biocompatibility is mainly attributed to small amount of Si ²⁺ and Mg ²⁺ released during the early degradation of the PEO coating.
Article
Zn-based biomaterials have emerged as promising new types of bioresorbable metallics applicable to orthopedic devices, cardiovascular stents, and other medical applications recently. Compared to other degradable metallic biomaterials (i.e. Mg- or Fe-based), Zn biomaterials have a more appropriate corrosion rate without hydrogen gas evolution. Here, we evaluated the potential of Zn-based metallics as medical implants, both in vitro and in vivo, alongside a standard benchmark Mg alloy, AZ31. The mechanical properties of the pure Zn were not strong enough, but were significantly enhanced (microhardness >70 kg/mm2, strength >220 MPa, elongation >15%) after alloying with Sr or Mg (1.5 at. %), surpassing the minimal design criteria for load-bearing device applications. The corrosion rate of Zn-based biomaterials was about 0.4 mm/year, significantly slower than that of AZ31. The measured cell viability and proliferation of three different human primary cells fared better for Zn-based biomaterials than AZ31 using both direct and indirect culture methods. Platelet adhesion and activation on Zn-based materials were minimal, significantly less than on AZ31. Hemolysis ratio of red cells (<0.5%) after incubation with Zn-based materials was also well below the ISO standard of 5%. Moreover, Zn-based biomaterials promoted stem cell differentiation to induce the extracellular matrix (ECM) mineralization process. In addition, in vivo animal testing using subcutaneous, bone, and vascular implantations revealed that the acute toxicity and immune response of Zn-based biomaterials were minimal/moderate, comparable to that of AZ31. No extensive cell death and foreign body reactions were observed. Taken together, Zn-based biomaterials may have a great potential as promising candidates for medical implants.
Article
Implanted biomaterials play a key role in the current success of orthopedic and dental procedures. Pure titanium and its alloys are the most commonly used materials for permanent implants in contact with bone. However, implant-related infections remain among the leading reasons for failure. The most critical pathogenic event in the development of infection on biomaterials is biofilm formation, which starts immediately after bacterial adhesion. In the last decade, numerous studies reported the ability of titanium surface modifications and coatings to minimize bacterial adhesion, inhibit biofilm formation and provide effective bacterial killing to protect implanted biomaterials. In the present review, the different strategies to prevent infection onto titanium surfaces are reported: surface modification and coatings by antibiotics, antimicrobial peptides, inorganic antibacterial metal elements and antibacterial polymers. Statement of Significance: Implanted biomaterials play a key role in the current success of orthopedic and dental procedures. Pure titanium and its alloys are the most commonly used materials for permanent implants in contact with bone. Microbial infection is one of the main causes of implant failure. Currently, the global infection risk is 2–5% in orthopedic surgery. Numerous solutions exist to render titanium surfaces antibacterial. The LBPS team is an expert on the functionalization of titanium surfaces by using bioactive polymers to improve the biologiocal response. In this review, the different strategies to prevent infection are reported onto titanium and titanium alloy surfaces such as surface modification by antibiotics, antimicrobial peptides, inorganic antibacterial metal elements and antibacterial polymers.
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Degradable metallic stents, most commonly comprised of Mg-based alloys, are of interest as an alternative to traditional metallic stents for application in the cardiac and peripheral vasculature. Two major design challenges with such stents are control of the corrosion rate and the acute presentation of a non-thrombogenic surface to passing blood. In this study, several types of sulfobetaine (SB)-bearing biodegradable polyurethanes were developed and assessed as physical, chemical and combination-type coatings for a model degradable Mg alloy, AZ31. For physical coatings, poly(ester sulfobetaine)urethane ureas, PESBUUs were synthesized using variable monomers that allowed the incorporation of a varying extent of carboxyl groups. Introduction of the carboxyl groups was associated with faster polymer degradation time. Simple physical coating of PESBUUs reduced macro- and microscopic thrombogenic deposition together with good stability of the coating attachment compared to a control coating of polylactic-co-gl¬¬¬¬ycolic acid. For PESBUUs incorporating carboxyl groups (PESBUUs-COOH), these groups could be converted to siloxane groups (PESBUUs-Si), thus creating polymers that could be surface reacted with the oxidized or phytic acid treated AZ31 surface. Chemical (silanization) attachment of these polymers reduced underlying alloy corrosion rates, but following the salination reaction with physical coating most reduced corrosion rates and protected the surface better from the consequences of oxidation occurring under the coating, such as blistering. The application of a multi-layered coating approach using a sulfobetaine-based biodegradable elastomer thus offers options for degradable metallic stent design where thromboresistance is desired in combination with a means to control both polymeric coating degradation rates and underlying alloy corrosion rates.
Article
Magnesium alloy has been generally accepted as an important biodegradable material on cardiovascular stent development for a long time. However, its limited biocompatibility, especially delayed endothelialization process restricts its further application. In this contribution, we modified the Mg-Zn-Y-Nd alloy surface with citric acid and dopamine via a layer-by-layer self-assembly assay, aiming at improving the biocompatibility of the magnesium alloy. The citric acid/dopamine (CA/PDA) layer exhibited a remarkable suppression of platelet activation/aggregation and thrombosis under 15 dyn/cm2 blood flowing. Inhibition on vascular smooth muscle cells growth and macrophages attachment/activation were also observed on this layer. In particular, the CA/PDA layer presented a promoted property for the vascular endothelial cells growth and spreading compared with the bare magnesium alloy, suggesting the pro-endotelialized function. In conclusion, this research may support potential application on surface modification of magnesium alloy based cardiovascular stents for better biocompatibility.
Article
Magnesium (Mg) alloys have been intensively investigated as potential absorbable coronary stent materials as their use avoids risks such as late inflammation and restenosis generated by permanent metallic implants. Besides that, clinical trials on coronary stents fabricated from Mg alloys have made great progress recently. However, the over-rapid corrosion rate, magnesium corrosion-induced thrombosis formation and delayed endothelium regeneration continue to be problematic for coronary artery stent therapy. In this study, silk fibroin blended with heparin and GREDVY (Gly-Arg-Glu-Asp-Val-Tyr) peptide was immobilized on a HF-pretreated MgZnYNd alloy surface via a polydopamine layer to improve its corrosion resistance, blood compatibility and endothelialization. Standard electrochemical measurements along with the long-term immersion results indicated that the functionalized MgZnYNd alloy had preferable anti-corrosion abilities compared with the bare MgZnYNd alloy. The modified surface exhibited outstanding hemocompatibility with reduced platelet adhesion, hemolysis rate and prolonged blood coagulation time. Human umbilical vein endothelial cell (HUVEC) and vascular smooth muscle cell (VSMC) co-culture results revealed more attached HUVECs on the functionalized samples than on the MgZnYNd alloy surfaces. The excellent corrosion retardation, hemocompatibility and re-endothelialization of the multi-functional coating indicate a promising method in the field of biodegradable magnesium-based implantable cardiovascular stents.
Article
During the last two decades, a great amount of researches have been focused on biodegradable metals. Technologies from alloy design to melting, manufacturing and processing, from microtube to stent laser processing and drug eluting coating have been improved and optimized continuously. Biodegradable metallic stent has evolved from a concept to a real product and generated three branches of material system. A large amount of animal tests and clinical tests have been carried out to investigate biodegradable magnesium stents. Results of clinical study have indicated that the magnesium stent is feasible, with favourable safety and performance outcomes. More importantly, Biotronik won CE Mark for Magmaris bioresorbable stent in 2016. Researches of biodegradable iron stents are still in the stage of animal tests. The nitrided iron stent possesses excellent mechanical properties. Results showed a good long-term biocompatibility of nitrided iron stent in rabbit and porcine model. Biodegradable zinc stent has only been introduced in recent years. Only a few in vivo studies have been reported with zinc wires implanted in rats. Results showed a good degradation behavior and biocompatibility of zinc wires. In this paper, the current research status of biodegradable metallic stents is reviewed, and the future research and development in mechanical property optimization, drug eluting and intelligence is proposed.
Article
Type 7N01 alloy has been widely applied in rail vehicles, but corrosion behavior and mechanical properties of this alloy after heat treatment or heat straightening becomes a limitation for its application. This paper reveals the effect of different numbers of heat treatments on corrosion behavior and mechanical properties of 7N01 alloy. With increasing the number of heat treatments, the corrosion susceptibility of 7N01 alloy increased. The evolution of corrosion behavior and mechanical properties of heat-treated samples was caused by modification of matrix precipitates and diffusion of Zn atom from matrix to grain boundaries.
Article
Ultrathin Si/Nb/Si trilayer is an excellent example of a system for which dimensionality effects, together with other factors like type of a substrate material and growth method, influence strongly its superconducting properties. This study offers some important insights into experimental investigation of density of states of such a system with the aim to identify an electronic structure of the interface as a function of niobium layer thickness. For that, two Si/Nb/Si trilayers with 9.5 and 1.3. nm thick niobium layer buried in amorphous silicon were studied using high-resolution (HR) XPS depth-profile techniques. Strong influence of sputtering was observed, which resulted in severe intermixture of Si and Nb atoms. Nevertheless, a sharp top interface and metallic phase of niobium were detected for the thicker layer sample. On the contrary, a Nb-rich mixed alloy at top interface was observed for the thinner layer sample.
Article
In the present study, pure zinc stents were implanted into the abdominal aorta of rabbits for 12 months. Multiscale analysis including micro-CT, scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and histological stainings was performed to reveal the fundamental degradation mechanism of the pure zinc stent and its biocompatibility. The pure zinc stent was able to maintain mechanical integrity for 6 months and degraded 41.75 ± 29.72% of stent volume after 12 months implantation. No severe inflammation, platelet aggregation, thrombosis formation or obvious intimal hyperplasia was observed at all time points after implantation. The degradation of the zinc stent played a beneficial role in the artery remodeling and healing process. The evolution of the degradation mechanism of pure zinc stents with time was revealed as follows: Before endothelialization, dynamic blood flow dominated the degradation of pure zinc stent, creating a uniform corrosion mode; After endothelialization, the degradation of pure zinc stent depended on the diffusion of water molecules, hydrophilic solutes and ions which led to localized corrosion. Zinc phosphate generated in blood flow transformed into zinc oxide and small amounts of calcium phosphate during the conversion of degradation microenvironment. The favorable physiological degradation behavior makes zinc a promising candidate for future stent applications.
Article
Staement of significance: Previous studies have shown zinc to be a promising candidate material for bioresorbable endovascular stenting applications. An outstanding question, however, is whether a zinc implant would ultimately passivate through the production of stable corrosion products or via a cell mediated tissue encapsulation process that prevented the diffusion of critical reactants and products at the metal surface. We found that zinc wires implanted in the murine artery exhibit steady corrosion for up to at least 20 months post-implantation. The results confirm earlier predictions that zinc stents could safely degrade within a time frame of approximately 1 - 2 years.
Article
The quantitative analysis of the chemistry at the surface of functional plasma polymers is highly important for the optimization of their deposition conditions and, therefore, for their subsequent applications. The chemical derivatization of amine and carboxyl-anhydride layers is a well-known technique already applied by many researchers, notwithstanding the known drawback of the derivatization procedures like side or uncomplete reactions that could lead to “unreliable” results. In this work, X-ray photoelectron spectroscopy (XPS) combined with epth profiling with argon clusters is applied for the first time to study derivatized amine and carboxyl-anhydride plasma polymer layers. It revealed an additional important parameter affecting the derivatization reliability, namely the permeation of the derivatizing molecule through the target analysed layer, i.e. the composite effect of the probe molecule size and the layer porosity. Amine-rich films prepared by RF low pressure plasma polymerization of cyclopropylamine were derivatized with trifluoromethyl benzaldehide (TFBA) and it was observed by that the XPS-determined NH2 concentration depth profile is rapidly decreasing over top ten nanometers of the layer. The anhydride-rich films prepared by atmospheric plasma co-polymerization of maleic anhydride and C2H2 have been reacted with, parafluoroaniline and trifluoroethyl amine. The decrease of the F signal in top surface layer of the anhydride films derivatized by the “large” parafluoroaniline was observed similarly as for the amine films but the derivatization with the smaller trifluoroethylamine (TFEA) led to a more homogenous depth profile. The data analysis suggests that the size of the derivatizing molecule is the main factor, showing that the very limited permeation of the TFBA molecule can lead to underestimated densities of primary amines if the XPS analysis is solely carried out at a low take-off angle. In contrast, TFEA is found to be an efficient derivatization agent of anhydride groups with high permeability through the carboxyl-anhydride layer.
Article
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 over-fast 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 PLGA layer. Surface microstructure was characterized by scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FT-IR). Nano-scratch 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 anti-corrosion behavior could be achieved by dense APTES barrier. Cell morphology and proliferation data demonstrated that APTES pre-treated group resulted in remarkedly 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 pre-treated Mg-Zn-Y-Nd stent implanted into porcine coronary arteries confirmed benign tissue compatibility as well as the well re-endothelialization without thrombogenesis or in-stent restenosis at 6-month followup.
Article
Novel pH-responsive biodegradable biomimetic nanocarriers were prepared by the self-assembly of N-acetyl-l-histidine-phosphorylcholine-chitosan conjugate (NAcHis-PCCs), which was synthesized via Atherton-Todd reaction to couple biomembrane-like phosphorylcholine (PC) groups, and N,N′-carbonyldiimidazole (CDI) coupling reaction to link pH-responsive N-acetyl-l-histidine (NAcHis) moieties to chitosan. In vitro biological assay revealed that NAcHis-PCCs nanoparticles had excellent biocompatibility to avoid adverse biological response mainly owing to their biomimetic PC shell, and DLS results confirmed their pH-responsive behavior in acidic aqueous solution (pH ≤ 6.0). Quercetin (QUE), an anti-inflammatory, antioxidant and potential anti-tumor hydrophobic drug, was effectively loaded in NAcHis-PCCs nanocarriers and showed a pH-triggered release behavior with the enhanced QUE release at acidic pH 5.5 compared to neutral pH 7.4. The results indicated that pH-responsive biomimetic NAcHis-PCCs nanocarriers might have great potential for site-specific delivery to pathological acidic microenvironment avoiding unfavorable biological response.
Article
Bioinspired double-positively charged phosphodicholine (PdC)-chitosan conjugate was synthesized via Atherton-Todd reaction, which can hydrolyze to zwitterionic phosphorylcholine (PC)-chitosan in basic solutions, confirmed by 1H and 31P NMR spectra. Thermal analysis revealed that there existed the freezing bound water due to the introduction of PdC and PC groups for both PdC-chitosan and PC-chitosan, implying that double-positively charged PdC-chitosan may exhibit excellent biocompatibility as zwitterionic PC-chitosan. Cytotoxicity, hemolysis and antibacterial activity evidenced that PdC-chitosan displayed high antibacterial activity against Escherichia coli and Staphylococcus aureus under physiological conditions, and very low cytotoxicity and hemolytic activity, owing to its highly selective lysis of bacterial membranes over mammalian cell membranes mainly resulting from the competition of electrostatic interactions and shielding effect of the restrained water of PdC, while biocompatible PC-chitosan showed no antibacterial activity due to its non-fouling property. The results indicated that biocompatible double-positively charged PdC-containing bioinspired polymers may provide a promising approach for developing safe and effective antibacterial agents.
Article
Zinc (Zn) and its alloys have recently been introduced as a new class of biodegradable metals with potential application in biodegradable vascular stents. Although an in vivo feasibility study pointed to outstanding biocompatibility of Zn–based implants in vascular environments, a thorough understanding of how Zn and Zn2+ affect surrounding cells is lacking. In this comparative study, three vascular cell types–human endothelial cells (HAEC), human aortic smooth muscle cells (AoSMC), and human dermal fibroblasts (hDF)—were studied to advance the understanding of Zn/Zn2+-cell interactions. Aqueous cytotoxicity using a Zn2+ insult assay resulted in LD50 values of 50 μM for hDF, 70 μM for AoSMC, and 265 μM for HAEC. Direct cell contact with the metallic Zn surface resulted initially in cell attachment, but was quickly followed by cell death. After modification of the Zn surface using a layer of gelatin—intended to mimic a protein layer seen in vivo—the cells were able to attach and proliferate on the Zn surface. Further experiments demonstrated a Zn dose-dependent effect on cell spreading and migration, suggesting that both adhesion and cell mobility may be hindered by free Zn2+.
Article
OBJECTIVE To improve the biocompatibility of stents using a phosphorylcholine coated stent as a form of biomimicry. INTERVENTIONS Implantation of phosphorylcholine coated (n = 20) and non-coated (n = 21) stents was performed in the coronary arteries of 25 pigs. The animals were killed after five days (n = 6), four weeks (n = 7), and 12 weeks (n = 8), and the vessels harvested for histology, scanning electron microscopy, and morphometry. MAIN OUTCOME MEASURES Stent performance was assessed by studying early endothelialisation, neointima formation, and vessel wall reaction to the synthetic coating. RESULTS Stent thrombosis did not occur in either group. Morphometry showed no significant differences between the two study groups at any time point. At five days both the coated and non-coated stents were equally well endothelialised (91% v92%, respectively). At four and 12 weeks there was no difference in intimal thickness between the coated and non-coated stents. Up to 12 weeks postimplant the phosphorylcholine coating was still discernible in the stent strut voids, and did not appear to elicit an adverse inflammatory response. CONCLUSION In this animal model the phosphorylcholine coating showed excellent blood and tissue compatibility, unlike a number of other polymers tested in a similar setting. Given that the coating was present up to 12 weeks postimplant with no adverse tissue reaction, it may be a potential candidate polymer for local drug delivery.
Article
A phospholipid/peptide polymer (PMMDP) with phosphorylcholine groups, endothelial progenitor cell (EPC)-specific peptides and catechol groups was anchored onto a titanium (Ti) surface to fabricate a biomimetic multifunctional surface. The PMMDP coating was characterized by X-ray photoelectron spectroscopy (XPS), water contact angle measurements and atomic force microscopy (AFM), respectively. The amount of PMMDP coating on the Ti surface was quantified by using the quartz crystal microbalance with dissipation (QCM-D). Interactions between blood components and the coated and bare Ti substrates were evaluated by platelet adhesion and activation assays and fibrinogen denaturation test using platelet rich plasma (PRP). The results revealed that the PMMDP-modified surface inhibited fibrinogen denaturation and reduced platelet adhesion and activation. EPC cell culture on the PMMDP-modified surface showed increased adhesion and proliferation of EPCs when compared to the cells cultured on untreated Ti surface. The inhibition of fibrinogen denaturation and platelet adhesion and support of EPCs attachment and proliferation indicated that this coating might be beneficial for future applications in blood-contacting implants, such as vascular stents.
Article
Due to their biodegradability, magnesium and magnesium based alloys could represent the third generation of biomaterials. However, their mechanical properties and time of degradation have to match application needs. Several approaches, such as choice of alloying elements or tailored microstructure, are employed to tailor corrosion behaviour. Due to the high electrochemical activity of Mg, numerous environmental factors (e.g., temperature and surrounding ion composition) are influencing its corrosion behaviour causing its unpredictability. Nevertheless, the need of reliable in vitro model(s) to predict in vivo implant degradation is increasing. In attempt to find a correlation between in vitro and vivo corrosion rates, this review presents a systematic literature survey as well as an attempt to correlate the different results. Copyright © 2014. Published by Elsevier Ltd.
Article
Biomimetic N-phosphorylcholine (PC)-chitosan derivatives (PCCs) with a phosphoramide linkage between glucosamine and PC in various degree of substitution (DS) were synthesized through Atherton–Todd reaction and subsequently hydrolysis under the mild conditions, and structurally characterized by 1H NMR, 31P NMR, FT-IR and GPC. The incorporation of zwitterionic PC groups modified the hydrophilic/hydrophobic balance of chitosan derivatives to induce the formation of nanosized micelles by self-assembly in neutral aqueous solution. Fluorescence measurements revealed that the critical aggregation concentration (CAC) of PCCs solutions increased with increasing the DS of PC. The physicochemical properties of PCCs aggregates in neutral aqueous solutions were investigated by AFM and dynamic light scattering (DLS). The results confirmed that the amphiphilic PCCs copolymers can self-assemble to form nanosized spherical micelles with zeta potential between 0 and 4 mV, suggesting that the PCCs nano-aggregates were mostly covered with electrically neutral zwitterionic PC groups. Furthermore, all the PCCs samples showed low toxicity against NIH/3T3 cells after incubated for 4 h or 24 h, indicating their safety for biomedical application.
Article
Five pure metals including Fe, Mn, Mg, Zn and W have been investigated on their corrosion behavior and in vitro biocompatibility by electrochemical measurement, static immersion test, contact angle measurement, cytotoxicity and hemocompatibility tests. It is found that the sequence of corrosion rate of five metals in Hank's solution from high to low is: Mg > Fe > Zn > Mn > W. Fe, Mg and W show no cytotoxicity to L929 and ECV304 cells, Mn induces significant cytotoxicity to both L929 and ECV304 cells, and Zn has almost no inhibition effect on the metabolic activities of ECV304 while largely reduces the cell viability of L929 cells. The hemolysis percentage of five pure metals is lower than 5% except for Mg and platelets adhered on Zn has been activated and pseudopodia-like structures can be observed while platelets on the other four metals keep normal.
Article
In this study, the corrosion performance of magnesium-based rare-earth containing alloy Mg–10Gd–3Y–0.5Zr (GW103) was evaluated in an ethylene glycol solution with a group of selected aliphatic, aromatic carboxylates and inorganic salts as inhibitors. The dependence of inhibition efficiency on the concentration ratio of sodium phosphate to sodium dodecylbenzenesulfonate (SDBS) and the total inhibitor concentration was measured by means of electrochemical techniques. It was found that the corrosion rate of GW103 decreased by addition of inorganic–organic inhibitors at both ambient and elevated temperatures. The inhibitors were more effective at the ambient temperature than at the elevated temperature. The corrosion of GW103 in the ethylene glycol solution can be effectively inhibited by 1000ppm of the inorganic–organic inhibitor mixture. It is believed that the added phosphate can interact with SDBS, resulting in a more compact surface film on the GW103 surface. Based on these results, as well as Environmental Scanning Electron Microscope (ESEM) observations, a synergistic mechanism was proposed to explain the inhibition behavior of the sodium phosphate+SDBS combination.
Article
An overview is given of the use of silanes for corrosion control of metals and bonding of silane treated metals to paint systems and rubber compounds. Examples are given of corrosion protection of cold rolled steel, galvanised steel, aluminium, and magnesium, both painted and unpainted. Emphasis in this work has been on the use of bis-silanes rather than the conventional mono-silanes. It is shown that mixtures of a bis-amino and a bis-polysulphur silane work with a wide range of metals and paint systems. A model is described which is largely based on electrochemical impedance spectroscopy (EIS) measurements.
Article
The strong surface hydration layer of nonfouling materials plays a key role in their resistance to nonspecific protein adsorption. Poly(sulfobetaine methacrylate) (polySBMA) is an effective material that can resist nonspecific protein adsorption and cell adhesion. About eight water molecules are tightly bound with one sulfobetaine (SB) unit, and additional water molecules over 8:1 ratio mainly swell the polySBMA matrix, which is obtained through the measurement of T(2) relaxation time by low-field nuclear magnetic resonance (LF-NMR). This result was also supported by the endothermic behavior of water/polySBMA mixtures measured by differential scanning calorimetry (DSC). Furthermore, by comparing both results of polySBMA and poly(ethylene glycol) (PEG), it is found that (1) the hydrated water molecules on the SB unit are more tightly bound than on the ethylene glycol (EG) unit before saturation, and (2) the additional water molecules after forming the hydration layer in polySBMA solutions show higher freedom than those in PEG. These results might illustrate the reason for higher resistance of zwitterionic materials to nonspecific protein adsorptions compared to that of PEGs.
Article
Human endothelial cells derived from umbilical cord blood (hCB-ECs) represent a promising cell source for endothelialization of tissue engineered blood vessels. hCB-ECs cultured directly above human aortic smooth muscle cells (SMCs), which model native and tissue engineered blood vessels, produce a confluent endothelium that responds to flow like normal human aortic endothelial cells (HAECs). The objective of this study was to quantify the elastic modulus of hCB-ECs cocultured with SMCs under static and flow conditions using atomic force microscopy (AFM). Cytoskeleton structures were assessed by AFM cell surface imaging and immunofluorescence of F-actin. The elastic moduli of hCB-ECs and HAECs were similar and significantly smaller than the value for SMCs in monoculture under static conditions (p<0.05). In coculture, hCB-ECs and HAECs became significantly stiffer with moduli 160-180% larger than their corresponding values in monoculture. While the moduli of hCB-ECs and HAECs almost doubled in monoculture and flow condition, their corresponding values in coculture declined after exposure to flow. Both the number and diameter of cortical stress fiber per cell width increased in coculture and/or flow conditions, whereas the subcortical stress fiber density throughout the cell interior increased by a smaller amount. These findings indicate that changes to biomechanical properties in coculture and/or exposure to flow are correlated with changes in the cortical stress fiber density. For ECs, fluid shear stress appeared to have greater effect on the elastic modulus than the presence of SMCs and changes to the elastic modulus in coculture may be due to EC-SMC communication.
Article
In the present work Zn-Mg alloys containing up to 3wt.% Mg were studied as potential biodegradable materials for medical use. The structure, mechanical properties and corrosion behavior of these alloys were investigated and compared with those of pure Mg, AZ91HP and casting Zn-Al-Cu alloys. The structures were examined by light and scanning electron microscopy (SEM), and tensile and hardness testing were used to characterize the mechanical properties of the alloys. The corrosion behavior of the materials in simulated body fluid with pH values of 5, 7 and 10 was determined by immersion tests, potentiodynamic measurements and by monitoring the pH value evolution during corrosion. The surfaces of the corroded alloys were investigated by SEM, energy-dispersive spectrometry and X-ray photoelectron spectroscopy. It was found that a maximum strength and elongation of 150MPa and 2%, respectively, were achieved at Mg contents of approximately 1wt.%. These mechanical properties are discussed in relation to the structural features of the alloys. The corrosion rates of the Zn-Mg alloys were determined to be significantly lower than those of Mg and AZ91HP alloys. The former alloys corroded at rates of the order of tens of microns per year, whereas the corrosion rates of the latter were of the order of hundreds of microns per year. Possible zinc doses and toxicity were estimated from the corrosion behavior of the zinc alloys. It was found that these doses are negligible compared with the tolerable biological daily limit of zinc.
Article
Three random copolymers poly(2-methacryloyloxyethyl phosphorylcholine-co-methacrylic acid) (PMAs) were synthesized by free radical polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) and methacrylic acid (MA) with different monomer ratios under monomer-starved conditions. The synthesized PMA polyanions were assembled on chitosan (CS) film surfaces via electrostatic interactions. Using layer by layer (LbL) assembly with PMA polyanion and chitosan polycation, PMA/CS multilayer thin films with phosphorylcholine groups on the outer surfaces were fabricated. The modified surfaces were characterized by dynamic contact angle (DCA), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Hemocompatibility of the surfaces was estimated by protein adsorption and platelet adhesion measurements. The results indicated that cell outer membrane mimetic structures were formed on the modified surfaces with PMA as the outermost layer, and the hemocompatibility of the modified surfaces was significantly improved. This facile method of fabricating cell outer membrane mimetic surfaces may have potential applications in the fields of hemocompatible coatings, drug delivery, and tissue engineering.
Article
Deposits of iron and hemosiderosis in the kidney have been observed in diseases with intravascular hemolysis, including paroxysmal nocturnal hemoglobinuria, and valvular heart diseases and prosthetic heart valve implants. However, the decrease in kidney function associated with hemolysis caused by cardiac valvular disease or prostheses is less well recognized. We present a case of intravascular hemolysis after repair and banding of the mitral valve that resulted in massive renal tubular deposition of hemosiderin with decreased kidney function. We discuss the pathophysiologic process of both acute and chronic tubular injury from heme and heme proteins, including injury to organelles resulting in autophagic vacuoles containing damaged organelles, such as mitochondria. We conclude that tubular injury resulting from heme proteins should be considered as a cause of decreased kidney function in all patients with a cardiac valvular disease or prosthesis.
Article
Erythrocytes are damaged or stimulated mechanically by artificial organs assisting in circulation. For several decades, a large number of research studies have been conducted to investigate the traumatizing phenomena due to nonphysiological flow conditions. These phenomena are thought to be the physical interaction between the cell membrane and the various fluidic conditions. To elucidate or evaluate the phenomena, however, chemical components emerging into the circulating solution, such as liberated hemoglobin or lactic dehydrogenase (LDH), have been measured as a main parameter. Naturally, the physical reaction caused on the membrane itself cannot be detailed by these parameters because they are the secondary products resulting from the mechanical membrane rupture. The aim of this study is to understand the traumatizing mechanism directly from a microbiological viewpoint. As a first step, we visualized the surface of sheep erythrocytes loaded with shear stress and measured erythrocyte surface roughness by atomic force microscopy (AFM) on a nanometer scale (10(-9) m). The constant shear rate was set at 1,800 (1/s), and the exposure time was set at 0.5, 1, and 2 h. We also measured the liberated hemoglobin concentration. As a result, it was found that the fine structure on the cell surface was changed drastically by the stress. It was also found that the surface roughness value increased with the exposure time, and correlated to the hemoglobin concentration. The visualization and the measurement of surface roughness of traumatized erythrocytes by AFM were thought to offer a new parameter for both hemolytic and subhemolytic studies.
Article
Circulating microparticles of various cell types are present in healthy individuals and, in varying numbers and antigenic composition, in various disease states. To what extent these microparticles contribute to coagulation in vivo is unknown. To examine the in vivo thrombogenicity of human microparticles. Microparticles were isolated from pericardial blood of cardiac surgery patients and venous blood of healthy individuals. Their numbers, cellular source, and tissue factor (TF) exposure were determined using flow cytometry. Their in vitro procoagulant properties were studied in a fibrin generation test, and their in vivo thrombogenicity in a rat model. The total number of microparticles did not differ between pericardial samples and samples from healthy individuals (P = 0.786). In both groups, microparticles from platelets, erythrocytes, and granulocytes exposed TF. Microparticle-exposed TF antigen levels were higher in pericardial compared with healthy individual samples (P = 0.036). Pericardial microparticles were strongly procoagulant in vitro and highly thrombogenic in a venous stasis thrombosis model in rats, whereas microparticles from healthy individuals were not [thrombus weights 24.8 (12.2-41.3) mg vs. 0 (0-24.3) mg median and range; P < 0.001]. Preincubation of pericardial microparticles with an inhibitory antibody against human TF abolished their thrombogenicity [0 (0-4.4) mg; P < 0.01], while a control antibody had no effect [19.6 (12.6-53.7) mg; P > 0.05]. The thrombogenicity of the microparticles correlated strongly with their TF exposure (r = 0.9524, P = 0.001). Human cell-derived microparticles promote thrombus formation in vivo in a TF-dependent manner. They might be the direct cause of an increased thromboembolic tendency in various patient groups.
Article
A novel approach for the surface modification of poly(acrylonitrile-co-2-hydroxyethyl methacrylate) (PANCHEMA) membranes by introducing phospholipid moieties is presented, which involved the reaction of the hydroxyl groups on the membrane surface with 2-chloro-2-oxo-1,3,2-dioxaphospholane (COP) followed by the ring-opening reaction of COP with trimethylamine. The chemical changes of phospholipid-modified acrylonitrile-based copolymers (PMANCP) membranes were characterized by Fourier transfer infrared spectroscopy and X-ray photoelectron spectroscopy. The surface properties of PMANCP membranes were evaluated by pure water contact angle, protein adsorption, and platelet adhesion measurements. Pure water contact angles measured by the sessile drop method on PMANCP membranes were obviously lower than those measured on the PANCHEMA membranes and decreased with the increase of the content of phospholipid moieties on the membrane surface. It was found that the bovine serum albumin adsorption and platelet adhesion were suppressed significantly with the introduction of phospholipid moieties on the membranes surface. These results demonstrated that the described process was an efficient way to improve the surface biocompatibility for the acrylonitrile-based copolymer membrane.
Adhesion, and Proliferation of Human Vascular Cells Exposed to Zinc
Adhesion, and Proliferation of Human Vascular Cells Exposed to Zinc, ACS Biomater. Sci. Eng. 2 (2016) 634-642.
Enhancing biocompatibility and corrosion resistance of biodegradable 16
  • J A Li
  • L Chen
  • X Q Zhang
  • S K Guan
J.A. Li, L.Chen, X.Q.Zhang, S.K. Guan, Enhancing biocompatibility and corrosion resistance of biodegradable 16