Compared with stainless steel and Co–Cr‐based alloys, Ti and its alloys are widely used as biomedical implants due to many fascinating properties, such as superior mechanical properties, strong ...corrosion resistance, and excellent biocompatibility. After briefly introducing several most commonly used biomedical materials, this article reviews the recent development in Ti alloys and their biomedical applications, especially the low‐modulus β‐type Ti alloys and their design methods. This review also systemically investigates the recently attractive progress in preparation of biomedical Ti alloys, including additive manufacturing, porous powder metallurgy, and severe plastic deformation, applied in the manufacturing and the influenced microstructures and properties. Nevertheless, there are still some problems with the long‐term performance of Ti alloys, and therefore several surface modification methods are reviewed to further improve their biological activity, wear resistance, and corrosion resistance. Finally, the biocompatibility of Ti and its alloys is concluded. Summarizing the findings from literature, future prediction is also conducted.
This paper reviews the recent development in Ti alloys and their biomedical applications, including additive manufacturing, porous powder metallurgy, and severe plastic deformation applied in the manufacturing and the influenced microstructures and properties. Nevertheless, some problems exist in long‐term performance of Ti alloys. Hence, several surface modification methods are reviewed to improve their biological activity, wear resistance, and corrosion resistance.
Lattice structures, which are also known as architected cellular structures, have been applied in various industrial sectors, owing to their fascinated performances, such as low elastic modulus, high ...stiffness-to-weight ratio, low thermal expansion coefficient, and large specific surface area. The lattice structures fabricated by conventional manufacturing technologies always involve complicated process control, additional assembly steps, or other uncontrollable factors. Furthermore, limited types of unit cells can be used to construct lattice structures when using conventional processes. Fortunately, additive manufacturing technology, based on a layer-by-layer process from computer-aided design models, demonstrates the unique capability and flexibility and provides an ideal platform in manufacturing complex components like lattice structures, resulting in an effective reduction in the processing time to actual application and minimum of material waste. Therefore, additive manufacturing relieves the constraint of structure design and provides accurate fabrication for lattice structures with good quality. This work systematically presents an overview of conventional manufacturing methods and novel additive manufacturing technologies for metallic lattice structures. Afterward, the design, optimization, a variety of properties, and applications of metallic lattice structures produced by additive manufacturing are elaborated. By summarizing state-of-the-art progress of the additively manufactured metallic lattice structures, limitations and future perspectives are also discussed.
Thanks to a considerable number of fascinating properties, titanium (Ti) and Ti alloys play important roles in a variety of industrial sectors. However, Ti and Ti alloys could not satisfy all ...industrial requirements; the degradation of Ti and Ti alloys always commences on their surfaces in service, which declines the performances of Ti workpieces. Therefore, with aim to further improve their mechanical, corrosion and biological properties, surface modification is often required for Ti and Ti alloys. This article reviews the technologies and recent developments of surface‐modification methods with respect to Ti and Ti alloys, including mechanical, physical, chemical, and biochemical technologies. Conventional methods have limited improvement in the properties and/or restriction on the geometry of workpieces. Therefore, many advanced surface‐modification technologies have emerged in recent decades. New methods make Ti and Ti alloys have better performance and extended applications. With requirement of high surface properties in future. Understanding the mechanism in various surface‐modification methods, combining the advantages of current technologies and developing new coating materials with high performance are required urgently. As such, incorporation of different surface‐modification technologies with high‐performance modified layers may be the mainstream of surface modifications for Ti and Ti alloys.
The technologies and recent development of surface‐modification methods for titanium (Ti) and Ti alloys are reviewed. Such technologies have expanded the applications of Ti and Ti alloys in the past and present due to their enhanced surface properties. Likewise, the mainstream of surface modifications for Ti and Ti alloys in the future is also discussed.
β-type titanium (Ti) alloys have attracted a lot of attention as novel biomedical materials in the past decades due to their low elastic moduli and good biocompatibility. This article provides a ...broad and extensive review of β-type Ti alloys in terms of alloy design, preparation methods, mechanical properties, corrosion behavior, and biocompatibility. After briefly introducing the development of Ti and Ti alloys for biomedical applications, this article reviews the design of β-type Ti alloys from the perspective of the molybdenum equivalency (Moeq) method and DV-Xα molecular orbital method. Based on these methods, a considerable number of β-type Ti alloys are developed. Although β-type Ti alloys have lower elastic moduli compared with other types of Ti alloys, they still possess higher elastic moduli than human bones. Therefore, porous β-type Ti alloys with declined elastic modulus have been developed by some preparation methods, such as powder metallurgy, additive manufacture and so on. As reviewed, β-type Ti alloys have comparable or even better mechanical properties, corrosion behavior, and biocompatibility compared with other types of Ti alloys. Hence, β-type Ti alloys are the more suitable materials used as implant materials. However, there are still some problems with β-type Ti alloys, such as biological inertness. As such, summarizing the findings from the current literature, suggestions forβ-type Ti alloys with bioactive coatings are proposed for the future development.
Floral homeotic transcription factors (TFs) act in a combinatorial manner to specify the organ identities in the flower. However, the architecture and the function of the gene regulatory network ...(GRN) controlling floral organ specification is still poorly understood. In particular, the interconnections of homeotic TFs, microRNAs (miRNAs) and other factors controlling organ initiation and growth have not been studied systematically so far. Here, using a combination of genome-wide TF binding, mRNA and miRNA expression data, we reconstruct the dynamic GRN controlling floral meristem development and organ differentiation. We identify prevalent feed-forward loops (FFLs) mediated by floral homeotic TFs and miRNAs that regulate common targets. Experimental validation of a coherent FFL shows that petal size is controlled by the SEPALLATA3-regulated miR319/TCP4 module. We further show that combinatorial DNA-binding of homeotic factors and selected other TFs is predictive of organ-specific patterns of gene expression. Our results provide a valuable resource for studying molecular regulatory processes underlying floral organ specification in plants.
The discovery of modern medicine relies on the sustainable development of synthetic methodologies to meet the needs associated with drug molecular design. Heterocycles containing difluoromethyl ...groups are an emerging but scarcely investigated class of organofluoro molecules with potential applications in pharmaceutical, agricultural and material science. Herein, we developed an organophotocatalytic direct difluoromethylation of heterocycles using O
as a green oxidant. The C-H oxidative difluoromethylation obviates the need for pre-functionalization of the substrates, metals and additives. The operationally straightforward method enriches the efficient synthesis of many difluoromethylated heterocycles in moderate to excellent yields. The direct difluoromethylation of pharmaceutical moleculars demonstrates the practicability of this methodology to late-stage drug development. Moreover, 2'-deoxy-5-difluoromethyluridine (F
TDR) exhibits promising activity against some cancer cell lines, indicating that the difluoromethylation methodology might provide assistance for drug discovery.
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•Corrosion behavior of laser powder bed fusion produced Ti–6Al–4V samples was investigated.•Static and dynamic Hank’s solutions were selected as the corrosion environments.•Flow ...solution degrades passive film of sample and thereby the corrosion resistance.•Flow solution promotes the deposition of calcium phosphate and hydroxyapatite.
The corrosion behavior of laser powder bed fusion produced (L-PBF-produced) titanium alloys involving flowing body fluid is still unclear. Therefore, this work investigates in vitro corrosion behavior and the characteristics of passive films formed on L-PBF-produced Ti–6Al–4V in both static and dynamic Hank’s solutions. Electrochemical measurements, immersion tests, X-ray photoelectron spectroscopy and scanning electron microscopy were conducted. In comparison to the L-PBF-produced Ti–6Al–4V in static Hank’s solution, the samples showed lower charge transfer resistance and higher passivation current density (anodic current density as well) in dynamic Hank’s solution. Meanwhile, a more apparent deposition of apatite and hydroxyapatite is found on the L-PBF-produced Ti–6Al–4V in dynamic Hank’s solution. Such outcomes mainly result from the enhancement of film/solution interfacial transportation in dynamic Hank’s solution. The dynamic Hank’s solution provides more calcium and phosphate ions to the surface of the passive film and also takes away the dissolved metal ions. Therefore, more salt deposition and a lower-quality passive film are found.
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•CoCrFeNiNbx HEA coatings with good metallurgical bonding were fabricated on pure Ti substrate.•The HEA coatings are consisted of BCC solid-solution phase and Laves phases (Cr2Ti and ...Cr2Nb).•Both Nb0 and Nb1 coatings have high hardness values of ~ 790 and ~ 1008 HV, respectively.•Such high hardness is attributed to combined contribution from specific microstructural characteristics.
CoCrFeNiNbx (x = 0 or 1 at.%) high-entropy alloy (HEA) coatings with good metallurgical bonding were successfully prepared on surfaces of pure titanium sheets by pulsed laser cladding. Phase constitutions and microstructural characteristics of the HEA coatings were characterized and analyzed by combined use of X-ray diffraction, electron channeling contrast imaging, energy dispersive spectroscopy and electron backscatter diffraction techniques. Results show that the HEA coating without Nb is consisted of BCC solid-solution phase with equiaxed bulk grain morphology and Cr2Ti Laves phase (C14-type hexagonal structure) with fine interdendritic lamellar morphology. After adding 1 at.% Nb, in addition to the BCC solid-solution phase and the Cr2Ti Laves phase, Cr2Nb Laves phase with C15-type cubic structure also appears in the interdendritic region in the HEA coating. Hardness tests reveal that the CoCrFeNiNbx HEA coatings are significantly harder than the pure titanium substrate (~122 HV). The hardness value of the HEA coating with 1 at.% Nb reaches 1008 HV, which is ~ 8.3 times that of the substrate and considerably higher than that of bulk HEAs with similar compositions. Such high hardness can be attributed to the combined contribution from solid-solution hardening, and hardening from grain refinement and Laves phases with fine lamellar morphologies.
Autophagy, a cellular self-eating mechanism, is important for maintaining cell survival and tissue homeostasis in various stressed conditions. Although the molecular mechanism of autophagy induction ...has been well studied, how cells terminate autophagy process remains elusive. Here, we show that ULK1, a serine/threonine kinase critical for autophagy initiation, is a substrate of the Cul3-KLHL20 ubiquitin ligase. Upon autophagy induction, ULK1 autophosphorylation facilitates its recruitment to KLHL20 for ubiquitination and proteolysis. This autophagy-stimulated, KLHL20-dependent ULK1 degradation restrains the amplitude and duration of autophagy. Additionally, KLHL20 governs the degradation of ATG13, VPS34, Beclin-1, and ATG14 in prolonged starvation through a direct or indirect mechanism. Impairment of KLHL20-mediated regulation of autophagy dynamics potentiates starvation-induced cell death and aggravates diabetes-associated muscle atrophy. Our study identifies a key role of KLHL20 in autophagy termination by controlling autophagy-dependent turnover of ULK1 and VPS34 complex subunits and reveals the pathophysiological functions of this autophagy termination mechanism.
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•ULK1 autophosphorylation promotes its recruitment to KLHL20 for ubiquitination•KLHL20 promotes ubiquitination of phagophore-residing VPS34 and Beclin-1•KLHL20 mediates autophagy termination by degrading ULK1 and VPS34 complex subunits•Impairment of autophagy termination causes cell death and muscle atrophy
Liu et al. report a function of the Cul3-KLHL20 ubiquitin ligase in a feedback regulation, leading to autophagy termination through the degradation of multiple subunits of ULK1 and VPS34 complexes. This mechanism is important for cell survival and muscle homeostasis.
Rechargeable aqueous Zn‐ion batteries (ZIBs) are regarded as one of the most promising devices for the next‐generation energy storage system. However, the uncontrolled dendrite growth on Zn metal ...anodes and the side hydrogen evolution reaction, which has not yet been well considered, hinder the practical application of these batteries. Herein, a uniform and robust metallic Sb protective layer is designed based on the theoretic calculation and decorated on Zn plate via in situ replacement reaction. Compared with the bare Zn plate, the as‐prepared Zn@Sb electrode provides abundant zincophilic sites for Zn nucleation, and homogenizes the electric field around the Zn anode surface, both of which promote the uniform Zn deposition to achieve a dendrite‐free morphology. Moreover, the Gibbs free energy (∆GH) calculation and in situ characterization demonstrate that hydrogen evolution reaction can be effectively suppressed by the Sb layer. Consequently, Sb‐modified Zn anodes exhibit an ultralow voltage hysteresis of 34 mV and achieve excellent cycling stability over 1000 h with hydrogen‐ and dendrite‐free behaviors. This work provides a facile and effective strategy to suppress both hydrogen evolution reaction and dendrite growth.
A uniform and robust metallic Sb protective layer is decorated on Zn plate via in situ replacement reaction. With rich zincophilic sites for Zn nucleation, improved electrolyte wettability and homogenized electric field, the Sb layer promotes the uniform Zn deposition with a dendrite‐free morphology. Moreover, the Gibbs free energy calculation and in situ characterization demonstrate that hydrogen evolution reaction can be effectively suppressed by the Sb layer.
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