Titanium (Ti) and its alloys are the most widely used materials for biomedical applications, owing to their good corrosion resistance, mechanical properties, and biocompatibility. However, their ...long-term performance is compromised by the post-surgery complications such as implant-associated infection and mechanical loosening. Surface modification can be adopted to alleviate these concerns while preserving the desirable bulk attributes. Among various techniques, electrochemical methods offer merits such as mild processing conditions, non-line-of-sight operation, low cost, as well as large-scale production. This paper gives a brief overview of surface engineering of the Ti-based alloys from the perspective of electrochemistry. It mainly focuses on three major electrochemical techniques: low voltage anodization, micro-arc oxidation, and electrodeposition. Overall, effects have been made to bring out a comprehensive understanding of electrochemical modification of Ti-based alloys for biomedical applications.
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Blood coagulation and inflammation are the earliest biological responses to implant surfaces. Implant nano‐surfaces can significantly impact the osseointegration through the influence on the early ...phase of bone regeneration. However, the interplay between blood clot property and inflammatory reaction on nanosurfaces is rarely understood. Herein, titania nanotube arrays (TNAs) with different diameters are fabricated on titanium. In vitro evaluation with the whole blood indicates that TNA with a diameter of 15 nm (TNA 15) enables noteworthy platelet activation resulting in distinct clot features compared with that of pure Ti and TNA with a diameter of 120 nm (TNA 120). Further co‐culture with macrophages on the clot or in the clot‐conditioned medium shows that the clot on TNA 15 downregulates the inflammation and manipulates a favorable osteoimmunomodulatory environment for osteogenesis. In vivo studies further demonstrate that TNA 15 could downregulate the inflammation‐related genes while upregulating growth metabolism‐related genes in an early healing hematoma. Additionally, TNA 15 promotes de novo bone formation with improved extending of osteocyte dendrites, demonstrating the desired osseointegration. These findings indicate that surface nano‐dimensions can significantly influence clot formation and appropriate clot features can manipulate a favorable osteoimmunomodulatory environment for bone regeneration and osseointegration.
Osseointegration, a sophisticated process starts immediately with blood clot formation on implants, which serves as a natural scaffold consisting of fiber structure and myriad cytokines derived from the platelet's activation, then initiates osteoimmunomodulation of macrophages. The study unravels the influence of distinct nano‐surface properties on clot features and demonstrates the adaptable clot features capable of steering osteoimmunomodulation targeting osseointegration.
We describe a strategy to fabricate a hydrogel-based microvascular construct by direct writing alginate bioink inside the viscous pre-polymer of hydrogels, which acts as a support bath. As the print ...needle translates through the polymers, the extruded alginate instantaneously forms calcium alginate hydrogel (Ca-Alg) templates deposited within the bath. This phase change allows the formed templates to be anchored within the pre-polymers, while maintaining their structure. After the printing process, the pre-polymers are solidified to form a mechanically robust hydrogel. Finally, a hydrogel construct with embedded microchannels is generated by liquefying and removing the Ca-Alg templates. Using this method, not only the alginate ink alone can be directly printed within the engineered constructs, but also the size and shape of the formed microchannels are controllable. Furthermore, a confluent endothelial layer for the generation of vascular networks can be constructed by adhering and proliferating endothelial cells on the channel linings. This strategy demonstrates a promising technique for rapid construction of in vitro vasculatures, which would provide a versatile platform for a wide array of applications such as tissue engineering, organ-on-a-chip and drug screening.
In this study, we have synthesized a series of multi-walled carbon nanotubes supported Pd, PdCu(molar ratio 1:1), PdSn(1:1) and PdCuSn(1:1:1) catalysts by chemical reduction with NaBH4 as a reducing ...agent. These catalysts are characterized using X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy (XPS), cyclic voltammetry and chronoamperometry. During the potential cycling activation, it is found that the additive Cu is prone to suffer leaching while the dissolution of Sn rarely occurs. Electrochemical measurements demonstrate that, the co-alloying of Pd with Cu and Sn can trigger the best catalytic activity enhancement as compared with the binary PdCu/CNTs, PdSn/CNTs and mono-component Pd/CNTs catalysts. The PdCuSn/CNTs reveals the most excellent activities toward methanol, ethanol and formic acid electro-oxidation and the corresponding mass activity can attain to 395.94, 872.70 and 534.83 mA mg−1 Pd, respectively. The possible promotion effect of additive Sn or/and Cu on the electrocatalytic activity improvement is also analyzed.
•Pd-based bi-/ternary catalysts were synthesized with Sn or/and Cu as alloying element.•PdCuSn/CNTs exhibits the highest activities for targeted molecules electro-oxidation.•Activity enhancement may derive from distinct effect by alloying with Cu and Sn.•Alloying of Sn is even more remarkable for ethanol and formic acid oxidation.
•Electropolishing (EP) pretreatment avoided pitting formation during anodization of NiTi alloy.•EP pretreatment extended Ni-Ti-O nanotube length.•EP pretreatment enhanced the corrosion resistance and ...antibacterial property of the nanotubes.
Ni-Ti-O nanotubes (NTs) anodically grown on nearly equiatomic NiTi alloy are promising in biomedical field, but mechanical polishing pretreatment of the substrate usually results in severe pitting. The present work proposes to use electropolishing (EP) as pretreatment of anodization of the NiTi alloy to eliminate the side effect of mechanical polishing. Scanning electron microscopy was used to observe the morphology of the samples. Potentiodynamic polarization test was carried out to evaluate the corrosion behavior. Biological experiments were performed to assay their cytocomaptibility and antibacterial ability. Our results show pitting can be completely avoided after substrate EP pretreatment, yielding a macro smooth surface, while micro ordered nanotubular structure is well preserved. EP pretreatment enhances the corrosion resistance and antibacterial ability of the NiTi alloy when compared with that of mechanically polished sample, and all the samples show no appreciable cytotoxicity, clearly indicating EP is a promising pretreatment for fabricating Ni-Ti-O NTs on the NiTi alloy for biomedical applications.
Incorporation of antibacterial agents (e.g. Ag and Cu) at the surface of biomedical materials has evolved as a potentially effective method for preventing the bacterial infections. However, the ...antibacterial efficacy of medical device implants must necessarily be balanced by good corrosion resistance and the corrosion behavior of the antibacterial coatings has seldom been reported. In this work, Zn-incorporated antibacterial TiO2 coating was produced on pure titanium (Ti) by micro-arc oxidization (MAO) and the electrochemical behavior was assessed. The results obtained from the antibacterial studies suggest that the Zn-incorporated TiO2 coating provides bactericidal activity against both Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) over 90%. The corrosion behavior of Zn-incorporated TiO2 coating were investigated using a combination of complementary electrochemical measurement techniques such as open circuit potential (OCP), potentiodynamic polarization and electrochemical impedance spectroscopy. The results show that the Zn-incorporated TiO2 coating move the OCP to the positive direction and increase the polarization resistance, thereby enhances the corrosion resistance of pure Ti. Collectively, the Zn-incorporated TiO2 coating with both antibacterial ability and anti-corrosive properties might be more suitable for biomedical surfaces.
•Cu–TiO2 coatings with different Cu concentrations were successfully prepared.•The Cu element is distributed throughout the entire coatings.•Cu mainly exists as CuO in the TiO2 coatings.•The Cu–TiO2 ...coatings exhibit excellent antibacterial activities.
Antibacterial TiO2 coatings with different concentrations of Cu (Cu–TiO2) were prepared by micro-arc oxidation (MAO) on pre-sputtered CuTi films. The effect of Cu concentrations in CuTi films on the MAO process was investigated. The Cu–TiO2 coatings were analyzed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The corrosion resistance of Cu–TiO2 coatings was evaluated via potentiodynamic polarization method. The antibacterial properties were assessed by two methods: spread plate method and fluorescence staining. The experimental results demonstrate that the coatings are porous and consist of anatase phase, rutile phase and unoxidized titanium. The CuTi films are almost completely oxidized and the thickness of all MAO coatings is about 5–10μm. Cu mainly exists as CuO in the TiO2 coatings. The Cu–TiO2 coatings exhibit excellent antibacterial activities, and the antibacterial rate gradually rise with the increase in Cu concentration in the MAO coatings. The corrosion resistance of MAO coatings is also improved slightly.
In this study, an oxide layer on Ti-based implants is fabricated by using a high current anodization (HCA) technique in the nitrate electrolyte. This layer is composed of micro-pits and nano-porous ...arrays in the honeycomb structure. The results show that both the roughness and the layer thickness are related to the reaction time, whereas the size of nano-pores has little to do with the anodization duration. Compared to the nano-tubular arrays constructed by the conventional anodization, this nano-porous layer shows significantly improved mechanical stability. Furthermore, the in vitro assay of osteoblasts shows that cells behaviors on this surface can be modulated by the topology of this special layer. A suitable hierarchical structure composed of micro-pits and nano-porous structure can significantly stimulate osteoblasts attachment, activity, spreading and ALP function. Therefore, this hierarchical surface layer may provide a promising approach, which endows the Ti-based implants with better stability and osseointegration.
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•Zn-1 wt%Mg-β-TCP composites with different β-TCP contents were fabricated by vacuum heating-press sintering.•Mg is embedded in the Zn substrate in the form of Zn2Mg and Zn11Mg2, ...while β-TCP particles were evenly distributed in the substrate.•The composites show high yield strength, degradation rate, and osteogenic activity when compared with that of pure zinc.
Repair of bone defects remains a major challenge in the field of orthopedics. Biodegradable zinc (Zn) has been considered as a revolutionary material for bone repair. However, it exhibits relatively poor mechanical strength and cytocompatibility as well as slow degradation rate, hindering its potential application as bone repair material. In the present work, biodegradable Zn-1 wt%Mg-nvol%β-TCP (n = 0, 1, 3, 5, 10) composites are fabricated via vacuum heating-press sintering to address the above concerns. The results show that the addition of magnesium (Mg) and beta-tricalcium phosphate (β-TCP) positively regulate the mechanical properties, degradation properties, and osteogenic activity of the composites. Zn-1 wt%Mg-3 vol%β-TCP possess the highest compressive yield strength of approximately 243.9 MPa compared with about 137.6 MPa of pure Zn. The in vitro corrosion rates of the Zn-1Mg-β-TCP composites are tunable between 0.428 and 0.546 mm/y. The 24-week in vivo experiments prove that the Zn-1Mg-β-TCP composites possess better osteogenic activity than that of pure Zn. In general, the Zn-1Mg-β-TCP composites exhibit suitable mechanical strength and degradation rate, coupled with their great biological activity, which are expected to provide reliable performance for clinical bone repair.
