The Cytocompatibility And Osteogenic Activity Of Biodegradable Zinc And Zinc Alloy Materials

Background and objective: Metal Zinc is one of the ideal metal materials for bone trauma repair,because of its good biological safety,mechanical properties and degradability.The purpose of this study is to explore the bone-promoting ability of zinc and zinc alloy materials and their related gene protein expression,bone trauma repair ability and biocompatibility through experimental studies in vivo and in vitro.It will serve as a new ideal orthopedic material for zinc materials in the future.This will provide the experimental support for the research and development of zine alloy as a new and ideal orthopedic implant.Methods: In order to improve the mechanical properties and osteogenic activity of pure zinc,an amount of alloying elements magnesium and copper(2wt.% each)were added to zinc to prepare binary or ternary zinc alloys.The experiment was divided into two parts: in vitro cell experiment and animal experiment.The in vitro cell experiment was divided into Zn,Zn-2Mg,Zn-2Cu,Zn-2Mg-2Cu experimental groups,a blank control group using common α-MEM full culture medium,and a positive control group using α-MEM full culture medium containing osteogenic components.In the direct experiment part,MC3T3-E1 cells were directly planted on the material display of each experimental group,and then dead-live staining was performed.In the indirect experiment part,MC3T3-E1 cells were co-cultured with the extracts of each experimental group and the culture medium of the control group.CCK-8 cell activity detection,alkaline phosphatase staining,alizarin red staining,RT-PCR,and protein electrophoresis experiments were carried out respectively.In the animal experiment part,6 adult male New Zealand rabbits were used as the research object to m ake the right femoral condyle bone defect model.They were divided into Zn-2Mg alloy porous stent experimental group and blank control group.Zn-2Mg alloy porous stent was implanted into the bone defect in the experimental group,while the bone defect was not filled in the blank control group.The rabbits were killed after 1month,and the images and histological staining were observed and evaluated.Results: In vitro direct contact test results show that MC3T3-E1 cells directly planted on the surface of th e Zn,Zn-2Mg,Zn-2Cu,Zn-2Mg-2Cu experimental group materials will gradually appear cell death.In the indirect experiment,the CCK-8 cell viability test results showed that the cell viability of the 20% and 10% concentration experimental groups was greater than 1 on the 5th day.In alkaline phosphatase staining and alizarin red staining experiments,the staining was more obvious in the 20%concentration experimental group,and the quantitative analysis results were statistically different(P<0.05).RT-PCR and protein electrophoresis showed that 20% concentration of Zn-2Mg and Zn-2Mg-2Cu constituted the up-regulation of ALP and Col1-α1 genes and proteins related to bone proliferation(P<0.05).There was no difference in the expression of RUNx-2 gene and prot ein related to bone differentiation in each experiment.In vivo experiments,the Zn-2Mg alloy porous scaffold was implanted into the rabbit femoral condyle defect model.Compared with the blank defect control group,the imaging results and hematoxylin-eosin staining method showed the femoral condyle defect in the Zn-2Mg alloy porous scaffold group At 1 month after surgery,new cortical bone and bone trabeculae are formed,and the effect of bone defect repair is better.Conclusion: The degradable zinc and zinc alloy materials showed good cytocompatibility in this experiment,and both had better bone-promoting properties than the blank control group.Within a suitable concentration range,the higher the zinc ion concentration,the better the proliferation,mineralization and migration ability of osteoblasts.Among them,the bone-promoting performance of the zinc-magnesium alloy group is better than that of the other experimental groups,which has good compatibility in the body and prom otes the repair of bone defects.Therefore,zinc-magnesium alloy material is expected to become a new choice of orthopedic implant materials,especially in the field of bone defect and fracture repair.