The Effect Of Hap:Eu³⁺ One-dimensional Nanomaterials On Bone Regeneration

The defects of bone tissues caused by diseases,injuries and tumors can be repaired by various substitutes.Substitutes include autogenous bone,allogeneic bone,heterogenous bone and synthetic materials.Although these substitutes have been used in clinical treatment,there are inevitable shortcoming such as immune rejection response and bone defect of donor site.Physician contributed to seek more suitable and effective substitutes,and bone tissue engineering?BTE?was presented.In recent years,bone tissue engineering has developed rapidly,and scaffold material is one of the four basic elements of BTE,which is the most easily controlled and studied element.In order to simulate the shape,structure and function of natural bone matrix,researchers have developed a large number of biomimetic composite scaffold materials by various processing techniques,but these scaffolds still have their own limitations.For example,the existing electrospinning scaffold material is mainly composed of lactic acid or polylactic acid,which have good biocompatibility and biodegradability,but the polymer may gradually degrade into acidic products and affect the surrounding tissues.Materials such as chitosan,hyaluronic acid and gelatin were introduced into bone tissue repair due to the similar organic collagen components of bone matrix,but their mechanical properties were insufficient.Hydroxyapatite[HAP,Ca₁₀?PO₄?₆?OH?₂],the main inorganic constituent of bone tissue,could be synthesized by different methods and have been widely used for bone substitute and replacement in biomedical application,such as surface coating,electrostatic spinning and 3D printing.Previous researches on bone induction of HAP are mostly concentrate on HAP composite scaffold materials,but few researchers have studied the own potential of HAP.In addition,homogeneous net-like structure and nanomaterials doped with luminescent elements have been rarely reported to explore the relationship between the position of materials relative to cells and the expression of bone-related proteins,as well as the bone induction effect between net-like structure and nanomaterials.Therefore,Eu³⁺-doped net-like structure assembled by HAP nanowires and Eu³⁺-doped HAP nanorods were synthesised by hydrothermal method in this paper,and a series of exploratory studies were carried out to observe bone induction effect in vitro and in vivo and the position of the materials relative to the cells.In our study,we synthesized Eu³⁺doped nanowires and nanorods.The HAP:Eu³⁺net-like structure was derived from nanowires by thiol–ene click reaction.The excellent cell biocompatibility of materials could be found by the detection of live/dead cell staining and MTT assay.Eu³⁺doped HAP materials could be used as fluorescent probe for cell imaging.In addition,the expression of alkaline phosphatase?ALP?and the formation of mineralized nodules were both studied by co-culture of cells and materials.The expression of bone-related proteins?Runx 2,OCN?and genes?Runx 2,Col?,OPN,OCN?were further investigated in vitro.The results of cell expression showed that both materials had bone induced ability,and the bone formation effect of net-like stucture was more obvious than that of nanorods group.The skull defect models of rats were constructed,and two kinds of hydroxyapatite were implanted into the bone defect to investigate and compare the induced bone formation in vivo.After bone induction for two months,the results of Micro-CT and H&E staining of the rat skull defect models showed that the two kinds of bone tissue engineering materials had the effect of repairing the defect in rats,and the new formed bone volume in the hydroxyapatite net-like structure group was larger than that in hydroxyapatite nanorods group.In vitro and in vivo,the experiments showed that HAP net-like structure could present better bone formation effect than nanorods.The rare earth doped hydroxyapatite can be used as a fluorescent probe to display the position between the two kinds of materials and cells.The position relationship between cells and materials may be a factor affecting bone formation.