Preparation and properties of porous Zn-based scaffolds as biodegradable implants: a review

In recent years, biodegradable porous Zn-based scaffolds employed as bone tissue engineering scaffolds to treat large bone defects have attracted attention of many researchers. Although porous Zn-based scaffolds have acceptable biocompatibility in vivo and more reasonable degradation rates than degradable Mg-based and Fe-based scaffolds, there is still a certain distance between the porous Zn-based scaffolds that have been developed and the ideal bone tissue engineering scaffolds. In this paper, the methods that had been used to prepare porous Zn-based scaffolds were summarized, and the advantages and disadvantages of each method were analysed. The mechanical properties of porous Zn-based scaffolds were reviewed, and the compressive, tensile, and fatigue behaviors of the scaffolds were also discussed. The degradation properties of porous Zn-based scaffolds in vitro were summarized, and the degradation rules were found. Comparing the degradation properties of bulk Zn-based materials and porous Zn-based scaffolds, the degradations of porous Zn-based scaffolds were more deeply understood. In addition, the degradation behaviors of porous Zn-based scaffolds in vivo were also reviewed. The antibacterial properties of porous Zn-based scaffolds were summarized. Reviewing the experimental results of the biocompatibility of porous Zn-based scaffolds in vitro and in vivo, the main factor affecting the biocompatibility was identified, and the reasons for the large gap between the biocompatibility results in vivo and in vitro were discussed. At last, the problems faced by the current porous Zn-based scaffolds used as bone tissue engineering scaffolds were proposed, and the potential solutions to these problems were also suggested. Graphical abstract