Synthesis Of Silver-and Strontium-doped Nano-Hydroxyapatite For Basic Study Of Bone Repair

It is urgent to introduce bone repair materials to restore bone integrity,fill gaps and enhance the ability of bone repair after bone defect due to injury or disease.The composition and structure of nano-hydroxyapatite?HA?are similar to those of bone mineral composition.HA has a natural advantage used in the repair of bone defects due to its high biocompatibility,strong osteoinduction,large specific surface area,good osteogenesis,good biodegradability,as well as good bone integration.The infection and inflammation are usually occur during bone repair,and the incorporation of silver and strontium in HA can prevent infection and promote the mineralization capacity of HA.In this paper,a series of nano-HA,silver-doped nano-HA,strontium-doped nano-HA and silver strontium co-doped HA were synthesized using EDTA disodium as the template.The morphology,structure and composition of different HA were characterized by TEM,SEM,XRD,FT-IR and EDS,respectively.The antibacterial properties of different HA were evaluated by using Escherichia coli?E.coli?and Staphylococcus aureus?S.aureus?.The effects of different HA on the cell viability,ALP levels and mineralized nodules,and the expression of inflammatory factors?TNF-? and IL-6?were evaluated using macrophages?RAW264.7?and osteoblasts?MC3T3-E1?,respectively.The results of this paper include the following three aspects:?1?The nano-HA and silver-doped nano-HA were synthesized.The results showed that: the synthesized materials were nano-solid rods with an average diameter of 60.1 ± 4.8 nm and an average length of 173.7 ± 8.5 nm.XRD and FTIR tests proved the formation of HA structure.Silver-doped nano-HA with different mass fraction has antibacterial effect on E.coli and S.aureus,and silver-doped nano-HA with higher silver doping mass fraction has better antibacterial effect.Silver-doped nano-HA were less toxic to macrophages and osteoblasts.Nano-HA and Ag_5.0HA promoted the expression of ALP and the differentiation of osteoblasts.The expression of ALP induced by HA and Ag_5.0HA was increased by 449.8% and 432.1%,respectively,compared with the OS group.The promotion effect of HA was higher than that of Ag_5.0HA..HA and Ag_5.0HA promoted the formation of mineralized nodules,and the mineralization induced by HA was 63.3% higher than that of OS group.The mineralization induced by Ag_5.0HA was 58.8% higher than that of OS group.Both HA and Ag_5.0HA inhibited the secretion of cytokine TNF-? in RAW264.7 cells.The inhibitory rates were 18.7% and 29.1%,respectively.The inhibitory effect of Ag_5.0HA was more significant.HA had no effect on the secretion of cytokine IL-6 in RAW264.7 cells,while Ag_5.0HA significantly inhibited the expression of IL-6,and the inhibition rate was 13.1%.?2?The nano-HA and strontium-doped nano-HA were synthesized.The results showed that: The synthetic material were nano-solid rod-shaped,the average diameter of strontium-doped nano-HA is 38.6 ± 2.2 nm and the average length is 135.3 ± 27.4 nm,which were lower than that of nano-HA.XRD and FTIR tests proved the formation of HA structure.Strontium-doped nano-HA has good biocompatibility.Nano-HA and Sr_5.0HA promoted the expression of ALP and the differentiation of osteoblasts.The ALP expression induced by HA and Sr_5.0HA was increased by 449.8% and 630.8%,respectively,compared with the OS group.The promotion effect of Sr_5.0HA was higher than that of HA,the ALP expression increased by 181.0%,comparatively.HA and Sr_5.0HA promoted the formation of mineralized nodules,and the mineralization induced by HA was 63.3% higher than that of OS group.The mineralization induced by Sr_5.0HA was 136.2% higher than that of OS group.Both HA and Sr_5.0HA inhibited the secretion of cytokine TNF-? in RAW264.7 cells.The inhibitory rates were 18.7% and 19.3%,respectively.The inhibitory effect of Sr_5.0HA was more significant.HA had no effect on the secretion of cytokine IL-6 in RAW264.7 cells,while Sr_5.0HA significantly inhibited the expression of IL-6,and the inhibition rate was 11.3%.?3?The nano-HA and silver/strontium co-doped nano-HA were synthesized.The results showed that: The synthetic material were nano-solid rod-shaped,silver strontium co-doped nano-HA average diameter and average length are lower than nano HA,The average diameter of silver strontium co-doped nano-HA is 37.0±4.8 nm and the average length is 109.1±20.0 nm,which were lower than that of nano-HA.XRD and FTIR tests proved the formation of HA structure.Silver strontium co-doped nano-HA with different mass fraction has antibacterial effect on E.coli and S.aureus,which better than that of silver-doped nano-HA.Silver strontium co-doped nano-HA were less toxic to macrophages and osteoblasts.Nano-HA and Ag_5.0Sr_5.0HA promoted the expression of ALP and the differentiation of osteoblasts.The ALP expression induced by HA and Ag_5.0Sr_5.0HA was increased by 297.1% and 451.1%,respectively,compared with the OS group,and the ability of Ag_5.0Sr_5.0HA to promote osteogenesis differentiation was better than that of HA,the ALP expression increased by 154.0%,comparatively.HA and Ag_5.0Sr_5.0HA promoted the formation of mineralized nodules,and the mineralization induced by HA was 63.3% higher than that of OS group.The mineralization induced by Ag_5.0Sr_5.0HA was 89.9% higher than that of OS group.Both HA and Ag_5.0Sr_5.0HA inhibited the secretion of cytokine TNF-? in RAW264.7 cells.The inhibitory rates were 18.7% and 36.0%,respectively.The inhibitory effect of Ag_5.0Sr_5.0HA was more significant.HA had no effect on the secretion of cytokine IL-6 in RAW264.7 cells,while Ag_5.0Sr_5.0HA significantly inhibited the expression of IL-6,and the inhibition rate was 10.2%.Silver/strontium co-doped nano-HA has the properties of antibacterial,anti-inflammatory and promote the differentiation and mineralization of osteoblasts.