Degradable Mg–Nd–Zn–Zr Alloy By Hydroxyapatite Coating To Enhance Tissue Regeneration:Evaluation In Vitro And Vivo

Objective: 1.To observe biological behavior and osteogenic differentiation of mouse embryonic cells in vitro;2.To observe osteogenesis in vivo.Methods: 1.In vitro using extracts of the blank,Ti alloy,JDBM,HA-JDBM cultured MC3T3-E1 cells.Cell Counting Kit-8(CCK-8)test detected cell proliferation.Flow cell apoptosis detected apoptosis.Polymerase Chain Reaction(PCR)detected ALP,COL I,OC and OPN gene expression.Immunofluorescence detected osteocalcin(OC)and transcription factors(RUNX2).2.Using Ti alloy,JDBM,HA-JDBM respectively to fix rats tibial fracture by using Van Gieson(V.G)to observe bone formation.Using X-ray,Micro-CT to observe degradation and bone morphogenetic changes.Results: 1? HA-JDBM group had maximum cellular activity,with an increasing trend before 6d.With the increasing of culture time,ALP expression showed an upward trend.JDBM group and HA-JDBM group were higher than blank group and Ti alloy group about the expression of ALP levels 2? Flow cell apoptosis showed HA-JDBM group had the highest proportion of cell survival,the lowest percentage of mortality and apoptotic cells,suggesting that HA-JDBM had good biocompatibility.3? Immunofluorescence showed three group had good cellular activity,without red stained cell.the content of OC and RUNX2 and cell proliferation were highest in HA-JDBM group.4? q RT-PCR showed that the expression of ALP,COL1,OC and OPN gene showed an increasing trend with time,the gene expression of HA-JDBM was better than other groups at the same time.5? JDBM group formed subcutaneous emphysema,with a small amount of hydrogen gas in the medullary cavity.Before 4 weeks,the fracture healing speed of JDBM group and HA-JDBM group was faster than the Ti alloy group.Micro-CT examination revealed that JDBM nail was broken down at 6 weeks,while Ti alloy group and the HA-JDBM nail could maintain good intact form,indicating that the degradation of JDBM was faster than HA-JDBM.6? Van Gieson(V.G)showed that there was a small gap between the intramedullary nail and new bone in JDBM group,while the Ti alloy group and HA-JDBM group had no obvious gap.Ti alloy group had less new bone formation,but HA-JDBM formed most new bone,with rule and compact bone trabecular.Conclusion: Compared with pure JDBM and Ti alloy,HA-JDBM showed excellent biocompatibility,higher advantage of osteogenic gene expression and tissue regeneration,and reduced the rate of degradation.Moreover,HA-JDBM group produced less gas.Finally,preliminary studies indicate that HA-JDBM is a promising biodegradable material for clinic.