Preparation Of Rare Earth Doped Hydrotalcite/Chitosan Scaffolds And Its Application In The Repair Of Osteoporotic Bone Defects

Osteoporosis?OP?is characterized by excessive osteoclast formation and osteogenic damage,resulting in limited bone regeneration and aseptic loosening of orthopedic implants.Repairing bone defects in the pathological state of osteoporosis is still a great challenge.Magnalium hydrotalcite/chitosan?MgAl-LDH/CS?scaffold materials are the basic framework and have good biocompatibility and bone conductibility for bone tissue engineering.the chemical composition of Mg²⁺plays an important role in regulating osteoblast and osteoclast differentiation of balance and maintaining bone metabolism,and becoming an effective method for reducing human potential risk factors for osteoporosis.In addition,trace amounts of rare earth elements such as gadolinium?Gd?,cerium?Ce?,europium?Eu?and lanthanum?La?are found in human bones,which play a key role in immune regulation and tissue,stem cell differentiation,metabolism and osteogenic activity.In this paper,rare earth doped?La/Gd?hydrotalcite/chitosan porous composite scaffolds?La/Gd-LDH/CS?were prepared by coprecipitation method and freeze-drying technology,and their bidirectional regulation on osteogenesis and osteoclast under the osteoporosis state were studied.Their structural?morphology?mechanical properties and in vitro degradation behavior were characterized by the testing means such as XRD,FTIR,SEM,TEM,electronic universal testing machine and ICP analysis etc.In vitro cell experiments and animal experiments in vivo revealed the influence mechanism of porous scaffolds doped with different contents of rare earth for bone.Rare earth doped hydrotalcite/chitosan scaffold materials were synthesized by using coprecipitation method and freeze-drying technology.The material had a three dimensional through macroporous and a hexagonal lamellar structure,and a mesoporous structure was formed by stacking between the pieces.Subsequently,the compressive properties of the scaffold material were tested and the good mechanical properties were demonstrated.The La-LDH/CS scaffold materials possess the pore diameter of 80-300?m,particle size of 50 nm and thickness of about 30 nm,distributing on the surface of the chitosan film.The Gd-LDH/CS composite scaffold materials have the pore diameter of 100-260?m,particle size of 40-60 nm and the thickness of about 30 nm,uniformly distributing on the wall of the scaffolds.Compared with pure LDH/CS scaffolds,the crystallinity changed after doping with La³⁺and Gd³⁺,but their morphology and structure were not affected.The ion release indicated that the slow release of rare earth ions at the appropriate concentration was beneficial to the cell growth while the scaffold materials were degraded.In vitro,La-LDH/CS and Gd-LDH/CS scaffolsterized rat bone marrow mesenchymal stem cells?OVX-rBMSCs?significantly enhanced cell proliferation and osteogenic differentiation by activating the Wnt/?-catenin signaling pathway,and promoted the expression of osteoblast related ALP,runx-2,OCN and col-1 genes.In addition,mouse bone marrow macrophage?BMMs?experiments showed that La/Gd-LDH/CS scaffold could inhibit rankl-induced osteoclast formation through NF-?B and MAPK signaling pathways,respectively.The OVX rat skull defect model of critical size further proves that the mineral deposition rates of La1/7-LDH/CS,La1/4-LDH/CS and LDH/CS scaffolds were?0.92±0.16 m/day?,?1.51±0.16 m/day?and?0.67±0.15 m/day?,respectively.The mineral deposition rates of Gd1/7-LDH/CS,Gd1/4-LDH/CS and LDH/CS scaffolds were?1.05±0.19 m/day?,?1.45±0.35 m/day?,and?0.5±0.19 m/day?,respectively.compared with the MgAl-LDH/CS scaffold,the La/Gd-LDH/CS scaffold generates more new bone tissue,indicating that it can promote more bone regeneration.The results showed that La/Gd-LDH/CS composite porous scaffold can promote osteogenic differentiation and inhibit osteoclast differentiation,and has excellent osteogenic properties,which become an ideal biomaterial for the treatment of osteoporotic bone defects.