Li Wan-Ying,Dai Yi-Long,Cai Wen-Hao,Lin Si-Han,Guo Lin,Zhang De-Chuang,Li Yuncang,Wen Cuie
Zn-Li alloys are considered promising candidate materials for biodegradable orthopedic implant applications due to their high mechanical performance and good biocompatibility. However, the presence of a large number of second-phase particles in this class of Zn alloys can lead to severe localized degradation due to micro-galvanic corrosion, which is detrimental to the mechanical integrity of the alloys during tissue healing in the human body. In this study, we report ultrahigh strength, uniform corrosion, good cytocompatibility, and effective antibacterial ability in Zn- x Li ( x = 0.3, 0.5, 0.7; wt%) alloys achieved through supersaturated solid solution treatment (SSST) at 375 °C under ultrahigh pressure of 3 GPa. A high concentration of β-LiZn 4 phases coexisted with the -Zn matrix in the as-cast Zn- x Li alloys, whereas almost all the Li dissolved into the -Zn matrix of SSST counterparts. The yield strength was 437 MPa for SSST Zn-0.3Li, 592 MPa for SSST Zn-0.5Li, and 686 MPa for SSST Zn-0.7Li. The SSST Zn-Li alloys showed uniform degradation with remarkably reduced degradation rates compared to their as-cast counterparts. The 25% concentration extracts of the Zn- x Li alloys demonstrated no cytotoxicity toward MC3T3-E1 cells, and the alloys exhibited effective antibacterial ability against methicillin-resistant staphylococcus aureus.
Shi Qiu,Fengdong Sun,Chen You,Chaokun Tang,Baoli Zhou,Shuquan Zhang,Jiangtao Feng,Aixian Tian,Minfang Chen
Through preparing the porous Zn-0.8Li scaffolds with 50–70 % porosity by using NaCl particles as pore-forming agents in the range of 150–350 µm and 350–550 µm with the infiltration casting method, the present study investigated the pore structure , mechanical properties and weight loss in simulated body fluids (SBF), and conducted the cellular activity and in vivo degradation experiments on porous Zn-0.8Li scaffolds before and after chitosan coating treatment. The results showed that the porous samples with small pore size had higher mechanical properties and lower degradation rate. However, with relatively higher average porosity and through-porosity, the porous samples with large pore size showed better pore connectivity, which provided channels for nutrient transport and promoted the lateral growth of internal tissues. In terms of cell experiments, chitosan coated Zn-0.8Li scaffolds with large pore size had better cell activity and adhesion. Since the coating of chitosan inhibited the release of Zn 2+ during the implantation of porous Zn-0.8Li scaffolds in vivo, it effectively promoted the growth of new bone tissue around the porous scaffolds, which provided an ideal microenvironment for the adhesion, proliferation and differentiation of MSCS. The results of this study demonstrated the great potential of chitosan coated porous biodegradable Zn-based scaffolds for bone tissue engineering.
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