The Study Of Inorganic Nano-Particle Materials And SE-coated 316L Stainless Steel With Nano-pit Arrays For Bone Defects Repair

Part Ⅰ THE STUDY OF INORGANIC NANO-PARTICLE MATERIALS FORBONE DEFECTS REPAIRBACKGROUND:Bone tissue engineering with biological materials,cells and growth factors has become an important research direction in the treatment of orthopedic reconstruction surgery,orthopedic chronic diseases and trauma-induced bone defects.Up to date,hydroxyapatite（HA）and beta-tricalcium phosphate（β-TCP）have been frequently used as tissue engineering materials for the treatment of bone defects due to their good biocompatibility and biological activity.However,it is not entirely satisfactory that HA andβ-TCP tissue engineering scaffolds show limited osteoinductivity,so they can not meet the therapeutic needs of patients with osteoporosis and metabolic disorders.In order to improve the mechanical properties for the repair ability of bone defects,the current research mainly includes the incorporation of various mechanical property enhancing materials（such as carbon nanotubes,graphene and boron nitride nanotubes）into biological materials.Recent years,rare earth elements（REEs）such as gadolinium（Ce）,strontium（Eu）,strontium（Sm）and strontium（La）have been detected in the human body to regulate human stem cell differentiation and metabolism and tissue regeneration.OBJECTIVE:In this experiment,nano-LaPO₄/CS and nano-GdPO₄/CS scaffolds derived from rare earth elements were synthesized and compared withβ-TCP/CS scaffolds to evaluate their physicochemical properties and bone defect repair ability.METHODS:LaPO₄ nanoparticles and GdPO₄ nanoparticles with diameters of 40-60 nm were prepared by chemical precipitation method.Then,based on this,they were mounted on a stack of chitosan,and the scaffolds were scanned by SEM and TEM.X-ray diffraction detection,fourier transform infrared spectroscopy were used to characterize their physical and chemical properties.In vitro,BMSCs were inoculated into scaffolds,and in vitro biocompatibility and in osteogenic differentiation ability were detected by SEM,CCK-8,ALP activity,ALP and alizarin red staining,RT-PCR and Western Bolt.The scaffold was implanted into the skull defect area of S-D rats in vivo,and the bone defect repair ability in vivo was determined by sequential fluorescent labeling,Micro-CT,histological staining and the like.RESULTS:LaPO₄ nanoparticles and GdPO₄ nanoparticles with diameters of 40-60 nm were successfully synthesized and loaded on chitosan scaffolds.In vitro results showed that nano-LaPO₄/CS and nano-GdPO₄/CS scaffolds had good in vitro biocompatibility and osteogenic differentiation compared with the controlβ-TCP/CS scaffold.At the same time,it was found that La could promote osteogenic differentiation of bone marrow mesenchymal stem cells through Wnt/β-catenin signaling pathway and induced high expression of osteogenic related genes alkaline phosphatase,osteocalcin and Collagen-I.Gd could promote osteogenic differentiation of BMSCs by activating the Smad/Runx2 model pathway.In vivo,both scaffold materials enhanced the repair of critical size skull defects and collagen deposition in rats compared to the control group.CONCLUSION:1.Nano-LaPO₄/CS and nano-GdPO₄/CS materials have good in vitro biological activity.Compared withβ-TCP/CS scaffold,nano-LaPO₄/CS and nano-GdPO₄/CS materials can significantly promote osteogenic differentiation and regeneration of new bone in vitro and in vivo.Part Ⅱ THE STUDY OF SE-COATED 316 L STAINLESS STEEL WITH NANOPIT ARRAYS FOR BONE DEFECTS REPAIRBACKGROUND: Fractures are one of the most common injuries.In recent decades,the incidence of fractures has increased dramatically.As the treatment of fractures,the huge economic burden of the health care system and individuals has been noticed.Currently,medical 316 L stainless steel materials are still widely used in various clinical operations because of their superior mechanical properties,corrosion resistance and relatively low price.However,there are still some clinical problems with the long-term implantation of 316 L stainless steel in the human body.In order to solve these problems,the surface modification of 316 L stainless steel is considered to be the most effective way to further improve the biological activity and friction properties of the modified material,and prevent internal fixation loosening or fracture.In previous studies,we found that nano-pits with a diameter of 50-60 nm can significantly enhance the adhesion and proliferation of cells.Therefore,the surface modification of 316 L stainless steel at the nanometer scale may also provide an excellent bioactive interface for cells in vivo and promote the osteogenesis ability of cells in vitro and in vivo.OBJECTIVE: In this experiment,the nano-pit arrays modification and nano-Se coating were performed on the surface of 316 L stainless steel,and compared with ordinary 316 L stainless steel materials,the physical and chemical properties and the repair ability of bone defects were evaluated.METHODS: 316 L stainless steel with nano-pit arrays Se coating was synthesized by electrochemical oxidation and nano-scale Se coating to enhance its surface properties,biocompatibility and osseointegration ability.The physical and chemical properties of the system were characterized by field emission scanning microscopy（FESEM）,energy dispersive X-ray spectroscopy（EDS）,X-ray photoelectron spectroscopy（XPS）and selenium release.In vitro,BMSCs were inoculated on the surface of the material,and in vitro biocompatibility and in vitro osteogenic differentiation ability were detected by SEM,immunofluorescence,CCK-8,ALP activity and RT-PCR.The stent was implanted into the femoral defect area of S-D rats in vivo,and the bone defect repair ability in vivo was detected by Micro-CT.RESULTS: This study successfully synthesized nano-pit arrays with a diameter of 50 nm,and nano-pit arrays with Se-coated 316 L stainless steel.In vitro results showed that 316 L stainless steel with nano-pit arrays had good in vitro biocompatibility and osteogenic differentiation compared with traditional 316 L stainless steel.More importantly,the Se coating couldupregulate the gene expression of OPN,RUNX-2 and ALP,indicating its outstanding cell compatibility and osteogenic differentiation ability.In vivo,Se-coated 316 L stainless steel with nano-pit arrays could better promote new bone formation in the body.CONCLUSION: 1.316 L stainless steel with nano-pit arrays has good biocompatibility and osteogenic differentiation ability compared with ordinary 316 L stainless steel.2.Se-coated 316 L stainless steel with nanopit arrays shows its osteogenic related genes are further up-regulated,indicating its good prospects in bone tissue engineering applications.