Development Of A Novel Bone Repair Material-Low Soluble Alendronate Calcium And Its Osteogenic Properties

The direct regulation of bone metabolism and reconstruction by materials is a potential development direction of novel bone repair materials.Alendronate salt,as a kind of small molecule compound that can regulate bone metabolism,has a good application prospect in clinic and bone tissue engineering.However,its strong water solubility leads to cytotoxicity,which limits its application in the field of bone repair to a certain extent.It is generally only used as a small molecule compound loaded on other bone repair materials,which is difficult to be directly used as a bone repair material.To strengthen the material properties of alendronate salt,based on the high affinity between alendronate groups and calcium ions,this study successfully developed low soluble alendronate calcium materials by chemical precipitation system,which solved the cytotoxicity problem caused by traditional alendronate salt due to its strong water solubility.The regulation of the material on the osteogenic differentiation of stem cells and osteoclast differentiation of macrophages and the effect of bone defect implantation were systematically studied.The results showed that the solubility of alendronate calcium was about 1000 times lower than that of alendronate sodium,which was the representative of traditional alendronate,and the material had no obvious cytotoxicity to adipose derived stem cells(ADSCs).Studies on the effect of alendronate calcium on osteogenic differentiation of stem cells and osteoclast differentiation of macrophages showed that the material could induce osteogenic differentiation of stem cells,mainly by up-regulating the expression of genes and proteins related to osteoblastic differentiation of ADSCs(ALP,RUNX2,COL-1,OPN and OCN),and the presence of calcium nodules.Besides,the material could inhibit the osteoclast differentiation process of macrophages(RAW264.7),mainly by down-regulating the enzyme activity of tartrate-resistant acid phosphatase and the expression of osteoclast differentiation specific genes(TRAP,CTSK and MMP-9).The results of in vivo experiments showed that alendronate calcium could induce osteogenic differentiation of stem cells in animals,mainly by up-regulating the expression of ADSCs osteogenic related genes(RUNX2,OPN).In addition,alendronate calcium showed a stronger osteogenic capacity in orthotopic bone repair,mainly by the material promoted the generation of new bone earlier than hydroxyapatite.The low soluble alendronate calcium developed in this study has solved the problem that the application of traditional alendronate is limited due to strong cytotoxicity caused by strong water solubility and strengthened its material properties.At the same time,the material has retained its biological activity of inducing stem cell osteogenesis and inhibiting osteoclast differentiation of macrophages,which is expected to be a novel bone repair material.