Zn-0.8 wt.% Li-0.1 wt.% Mn wire with the diameter of 0.3 mm was fabricated and further processed into gastrointestinal staple, and its in vitro and in vivo biodegradation behavior and biocompatibility were studied systematically. The experimental Zn-Li-Mn alloy staple could deform from the original U-shape to B-shape without fracture, indicating its good mechanical property. Due to the residual stress concentration caused by anastomosis deformation, the feet and leg arc part of the staple were more prone to degradation. The Zn-Li-Mn alloy staple sustained integrity after immersion in Hanks' solution and simulated gastric fluid (SGF) for 28 days, and the degradation rate in SGF was about 4 times of that in Hanks' solution. Furthermore, Zn-Li-Mn alloy staples were utilized for gastrointestinal anastomosis in pig models, with clinically-used titanium alloy staples as a comparison. No anastomotic leakage and severe inflammation were observed after operation. The Zn-Li-Mn alloy staple maintained mechanical integrity within 8 weeks' implantation. The gastrointestinal tissue healed after 12 weeks, and no obvious side effects were detected during the whole implantation period, demonstrating the good biocompatibility of Zn-Li-Mn alloy staple. Thus, Zn-Li-Mn alloy staple fabricated in this work displayed the promising potential in the gastrointestinal anastomosis.Copyright © 2020. Published by Elsevier Ltd.

Zinc (Zn) and its alloys have been proposed as biodegradable implant materials due to their unique combination of biodegradability, biocompatibility, and biofunctionality. However, the insufficient mechanical properties of pure Zn greatly limit its clinical application. Here, we report on the microstructure, mechanical properties, friction and wear behavior, corrosion and degradation properties, hemocompatibility, and cytocompatibility of Zn-3Cu and Zn-3Cu-0.2Ti alloys under three different conditions of as-cast (AC), hot-rolling (HR), and hot-rolling plus cold-rolling (HR + CR). The HR + CR Zn-3Cu-0.2Ti exhibited the best set of comprehensive properties among all the alloy samples, with yield strength of 211.0 MPa, ultimate strength of 271.1 MPa, and elongation of 72.1 %. Immersion tests of the Zn-3Cu and Zn-3Cu-0.2Ti alloys in Hanks’ solution for 3 months indicated that the AC samples showed the lowest degradation rate, followed by the HR samples, and then the HR + CR samples, while the HR + CR Zn-3Cu exhibited the highest degradation rate of 23.9 μm/a. Friction and wear testing of the Zn-3Cu and Zn-3Cu-0.2Ti alloys in Hanks’ solution indicated that the AC samples showed the highest wear resistance, followed by the HR samples, and then the HR + CR samples, while the AC Zn-3Cu-0.2Ti showed the highest wear resistance. The diluted extracts of HR + CR Zn-3Cu and Zn-3Cu-0.2Ti at a concentration of ≤25 % exhibited non-cytotoxicity. Furthermore, both the HR + CR Zn-3Cu and Zn-3Cu-0.2Ti exhibited effective antibacterial properties against S. aureus.

Appropriately adapted comprehensive mechanical properties, degradation behavior and biocompatibility are prerequisites for the application of Zn-based biodegradable implants. In this study, hot-extruded Zn-0.5Cu-xFe (x = 0.1, 0.2 and 0.4 wt%) alloys were fabricated as candidates for biodegradable materials for guided bone regeneration (GBR) membranes. The hot-extrusion process and Cu alloying were expected mostly to enhance the mechanical properties, and the Fe alloying was added mainly for regulating the degradation. The microstructure, mechanical properties and degradation behavior were systematically investigated. The ZnCuFe alloys were composed of a Zn matrix and FeZn phase. With increasing Fe content, a higher FeZn phase precipitation with larger particles was observed. Since elongation declined significantly until fracture with increasing Fe content up to 0.4 wt%, the ZnCuFe (0.2 wt%) alloy achieved a good balance between mechanical strength and ductility, with an ultimate tensile strength of 202.3 MPa and elongation at fracture of 41.2%. Moreover, the addition of Fe successfully accelerated the degradation of ZnCuFe alloys. The ZnCuFe (0.2 wt%) alloy showed relatively uniform corrosion in the long-term degradation test. Furthermore, extracts of the ZnCuFe (0.2 wt%) alloy showed no apparent cytotoxic effects against L929 fibroblasts, Saos-2 osteoblasts or TAg periosteal cells. The ZnCuFe (0.2 wt%) alloy exhibited the potential to inhibit bacterial adhesion of and mixed oral bacteria. Our study provides evidence that the ZnCuFe (0.2 wt%) alloy can represent a promising material for the application as a suitable GBR membrane.© 2020 [The Author/The Authors].

Bone defects are commonly caused by severe trauma, malignant tumors, or congenital diseases and remain among the toughest clinical problems faced by orthopedic surgeons, especially when of critical size. Biodegradable zinc-based metals have recently gained popularity for their desirable biocompatibility, suitable degradation rate, and favorable osteogenesis-promoting properties. The biphasic activity of Sr promotes osteogenesis and inhibits osteoclastogenesis, which imparts Zn-Sr alloys with the ideal theoretical osteogenic properties. Herein, a biodegradable Zn-Sr binary alloy system was fabricated. The cytocompatibility and osteogenesis of the Zn-Sr alloys were significantly better than those of pure Zn in MC3T3-E1 cells. RNA-sequencing illustrated that the Zn-0.8Sr alloy promoted osteogenesis by activating the wnt/β-catenin, PI3K/Akt, and MAPK/Erk signaling pathways. Furthermore, rat femoral condyle defects were repaired using Zn-0.8Sr alloy scaffolds, with pure Ti as a control. The scaffold-bone integration and bone ingrowth confirmed the favorable in vivo repair properties of the Zn-Sr alloy, which was verified to offer satisfactory biosafety based on the hematoxylin-eosin (H&E) staining and ion concentration testing of important organs. The Zn-0.8Sr alloy was identified as an ideal bone repair material candidate, especially for application in critical-sized defects on load-bearing sites due to its favorable biocompatibility and osteogenic properties in vitro and in vivo.© 2020 [The Author/The Authors].

In recent years, Zn-based materials provide a new option as biodegradable metals for orthopedic applications. To improve the low strength and brittle nature of pure Zn, small amounts of alloying element Mn (0.1, 0.4 and 0.8 wt.%) were added into Zn to fabricate binary Zn-Mn alloys. An extremely high elongation (83.96 ± 2.36%) was achieved in the resulting Zn-0.8 wt.%Mn alloy. Moreover, Zn-Mn alloys displayed significantly improved cytocompatibility as compared to pure Zn, according to cell proliferation and morphology analyses. More importantly, a significantly improved osteogenic activity was verified after adding Mn regarding ALP activity and osteogenic expression. Furthermore, Zn-0.8 wt.%Mn alloy scaffolds were implanted into the rat femoral condyle for repairing bone defects with pure Ti as control. Enhanced osteogenic activities were confirmed for Zn-0.8Mn alloy in contrast to pure Ti based on Micro-CT and histological results, and favorable in vivo biosafety of Zn-0.8Mn alloy was verified by H&E staining and blood tests. The exceptional mechanical performance and favorable osteogenic capability render Zn-Mn alloy a promising candidate material in the treatment of bone defects or fracture repair. STATEMENT OF SIGNIFICANCE: The element Mn, on the one hand, as an essential trace element in the human body, promotes cell proliferation, adhesion, spreading, and regulates bone metabolism; on the other hand, it could significantly improve the ductility of Zn alloys. Here, we systematically reported the biocompatibility and biofunctionality of binary biodegradable Zn-Mn alloys in the bone environment. The Zn-Mn alloys promoted MC3T3-E1 cell proliferation, adhesion, spreading, and osteogenic differentiation in vitro. Furthermore, a rat femoral condyle defect model was established; porous Zn-Mn alloy scaffolds were manufactured to repair the bone defects. Significant bone regenerations, considerable bone ingrowth, and desirable biosafety were confirmed in vivo. Therefore, biodegradable Zn-Mn with promising osteogenic properties may become new options for orthopedic implant materials.Copyright © 2020. Published by Elsevier Ltd.

Alloying combined with plastic deformation processing is widely used to improve mechanical properties of pure Zn. As-cast Zn and its alloys are brittle. Beside plastic deformation processing, no effective method has yet been found to eliminate the brittleness and even endow room temperature super-ductility. Second phase, induced by alloying, not only largely determines the ability of plastic deformation, but also influences strength, corrosion rate and cytotoxicity. Controlling second phase is important for designing biodegradable Zn alloys. In this review, knowledge related to second phases in biodegradable Zn alloys has been analyzed and summarized, including characteristics of binary phase diagrams, volume fraction of second phase in function of atomic percentage of an alloying element, and so on. Controversies about second phases in Zn-Li, Zn-Cu and Zn-Fe systems have been settled down, which benefits future studies. The effects of alloying elements and second phases on microstructure, strength, ductility, corrosion rate and cytotoxicity have been neatly summarized. Mg, Mn, Li, Cu and Ag are recommended as the major alloying elements, owing to their prominent beneficial effects on at least one of the above properties. In future, synergistic effects of these elements should be more thoroughly investigated. For other nutritional elements, such as Fe and Ca, refining second phase is a matter of vital concern.© 2020 Production and hosting by Elsevier B.V. on behalf of KeAi Communications Co., Ltd.