| Zinc alloy porous scaffolds are expected to be the next generation of degradable orthopedic implants attributed to their moderate degradation rate and antibacterial effect.Traditional preparation methods of zinc alloy porous scaffolds,such as powder metallurgy,hot pressing sintering and seepage casting,are difficult to control the pour structure of porous scaffolds,which limits the controllability of the service performance of porous scaffolds.Additive manufacturing techniques for the preparation of metal porous scaffolds,such as selective laser melting(SLM)and laser powder bed fusion(L-PBF),can regulate the structure of porous scaffolders.However,the evaporation and sputtering of Zn occur during the preparation process due to the low melting point of Zn itself,resulting in many defects and poor mechanical properties of the final prepared samples.To solve these problems,a new method combining VAT photopolymerization and casting was developed in this study to prepare Zn-1Mg porous scaffolds with three-period minimal surface(TPMS)structure.The prepared Zn-1Mg porous scaffolds have completely connected pore structure and controllable topological structure,and then the characterization analysis and various properties of the scaffolds were carried out.The main conclusions are as follows:(1)In this work,three different TPMS microporous units were constructed by mathematical modeling method,and the parametric control of microporous structure was realized.It was found that the stress and strain distribution of TPMS gyroid structure under stress was more uniform,and the small difference in stress environment of bone implantation scaffold under service condition was more beneficial to the proliferation and differentiation of cells and the regeneration of new bone.(2)In this work,a new preparation process combining VAT photopolymerization and casting was developed and explored,and three kinds of porous Zn-1Mg scaffolds with TPMS gyroid structure of 650 μm,800 μm and 1040 μm were successfully prepared with reasonable process parameters.The process avoids the evaporation of Zn and Mg in porous Zn-Mg alloy scaffolds prepared by SLM,and which is a simple and effective preparation method for porous Zn-Mg scaffolds.(3)The mechanical properties of porous scaffolds can be changed by adjusting their topological design.The mechanical properties of porous scaffolds decrease with the increase of porosity.Under the same porosity condition,G06 porous scaffolds with smaller pore diameter have better elastic modulus(1.54 GPa)and yield strength(26.91 MPa).(4)The biodegradation rate of Zn-1Mg porous scaffolds was moderate,and the weight loss was 7.89%-13.16% after 90 days of biodegradation in vitro.G06(650 μm)porous scaffolds with smaller pore size induced more calcium and phosphorus compounds during the degradation process,which was conducive to bone healing and regeneration.After 90 days of degradation,the mechanical properties of G06-G10 porous scaffolds were still within the range of cancellous bone,which met the requirements of physical properties of orthopedic implants.At the same time,corrosion products produced during the long-term degradation of Zn-1Mg porous scaffolds can maintain or even improve the mechanical properties of porous scaffolds.(5)Compared with G08 and G10,G06 porous scaffolds showed better cytocompatibility.Cultured with 50% and 25% extracts for 2 days,the viability of G06 cells reached 120%.The cellular compatibility of biological scaffolds can be improved by adjusting the topology of porous scaffolds.(6)Zn-1Mg scaffold has good antibacterial activity,and the antibacterial rate against Staphylococcus aureus and Escherichia coli can reach 99%.With good cytocompatibility and antibacterial properties,G06 scaffold is a promising biodegradable orthopedic implant material. |
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