Preparation and properties of biodegradable porous Zn-Mg-Y alloy scaffolds

In the field of metal-based bone tissue engineering scaffolds, porous Zn-based scaffolds are expected to be one of the most promising biodegradable bone tissue engineering scaffolds due to their acceptable biocompatibility and more suitable degradation rate compared with Mg-based and Fe-based scaffolds. However, the poor mechanical strength of porous pure Zn scaffolds limits their clinical applications. To improve the mechanical properties of porous Zn scaffolds, alloying treatment has become a feasible method. In this work, porous Zn-Mg-Y alloy scaffolds were prepared by an air pressure infiltration (API) method using NaCl particles as spacing holders. The phase structures, microstructures, compressive mechanical properties, degradation properties, antibacterial abilities as well as cytotoxicity of the obtained porous Zn-Mg-Y alloy scaffolds were investigated. The experimental results suggest that the alloy scaffolds contain strengthening phases such as MgZn2 and/or Mg2Zn11 as well as Y-rich phases. Under the action of these strengthening phases, the porous Zn-Mg-Y alloy scaffolds exhibit better mechanical properties. In vitro degradation tests indicate that the strengthening phases such as MgZn2 and Mg2Zn11 in the alloy scaffolds can be preferentially degraded as sacrificial anodes. Correspondingly, the degradation rates of the porous Zn-Mg-Y alloy scaffolds in simulated body fluid (SBF) have been accelerated. Antibacterial tests imply that the porous Zn-Mg-Y alloy scaffolds possess excellent antibacterial ability against Escherichia coli similar to the porous pure Zn scaffolds. Cytotoxicity tests show that the Zn2+ concentrations in the 100% extracts prepared from the porous Zn-Mg-Y alloy scaffolds (not including Zn-3Mg-0.5Y alloy scaffold) were all lower than that prepared from the porous pure Zn scaffold. The 25% and 10% extracts prepared from all the porous Zn-Mg-Y alloy scaffolds exhibit excellent cellular activity on MC3T3-E1 cells. In summary, the porous Zn-Mg-Y alloy scaffolds have the potential to be used as bone tissue engineering scaffolds to withstand relatively large loads.