Preparation And Role Of Immunomodulatory Mesoporous Bioactive Glass Materials In Bone Repair

In traditional bone tissue engineering and regenerative medicine,specific tissue regenerative cells such as stem cells,osteoblasts or endothelial cells have been regarded as key target cells to promote bone regeneration and reconstruction.In designing and preparing related biomaterials,researchers mostly focus on the effect of materials on target cells.Recent studies have revealed that immune cells,especially macrophages,are also important participants in the process of bone regeneration.In this study,from the perspective of macrophage immunomodulation,we propose a dual release strategy of ions and antiinflammatory drugs or proteins based on bioactive glass materials,through the controlled regulation of macrophage polarization phenotype,in order to achieve immunomodulation of osteogenesis.This project investigated immunomodulatory mesoporous bioactive glass(MBG)and its composite scaffold material in detail,focusing on elucidating the mechanism of osteogenic effect of the material on bone tissue-related cells indirectly through regulating macrophage polarization,establishing a relevant animal model of bone defects,and verifying the osteogenic repair effect at the injury site under the immunomodulation of the material.The main research work and conclusions are as follows:(1)MBG with uniform size and regular morphology was prepared by the combination of sol-gel and organic template cetyltrimethylammonium bromide(CTAB).The surface of CDMBG was further modified by β-cyclodextrin(β-CD).It has good biomineralization activity in vitro.In addition,a novel immunomodulatory mesoporous bioactive glass,NG@CD-MBG,was constructed by loading the anti-inflammatory drug naringin(NG),and the controlled local release of NG enabled NG@CD-MBG to regulate the polarization of macrophages toward the M2 phenotype(anti-inflammatory type)and to trigger its anti-inflammatory effect.In addition,NG@CD-MBG could also promote osteogenic differentiation of stem cells and inhibit the formation of osteoclasts by constructing the local immune microenvironment for osteogenesis,and finally achieve good osteogenic effects.In vivo experiments in rats with femoral defects further confirmed that immunomodulatory NG@CD-MBG could efficiently promote new bone regeneration at the site of bone defects.(2)In order to better realize the application of new immunomodulatory NG@CD-MBG,inspired by the structure of natural bone,we prepared NG@CD-MBG/ silk fibroin(SF)composite nanofiber membrane scaffold by electrostatic spinning bionanotechnology.NG@CD-MBG/SF nanofibrous membranes have good hydrophilicity,can stably and continuously release NG as well as bioactive ions,and have biomineralization activity to induce hydroxyapatite deposition.NG@CD-MBG/SF nanofibrous membranes can induce macrophages to polarize to M2 phenotype and significantly inhibit the expression of proinflammatory factors.Macrophage conditioned medium regulated by NG@CD-MBG/SF nanofibrous membranes can significantly enhance the ALP activity and osteogenic differentiation ability of mBMSCs.Experiments on critical bone defects in rat skull confirmed that NG@CD-MBG/SF nanofibrous membranes exerted immunomodulatory effects by stimulating macrophages,and effectively guided bone regeneration,accelerated the bone repair process,and promoted improvement in the quality of new bone.(3)In order to realize the sequential polarization of M0(inactivated)→M1(proinflammatory)→M2(anti-inflammatory)of macrophages by novel immunomodulatory mesoporous bioactive glass,immunomodulatory IFN-γ@Sr-MBG was designed and synthesized in this study.Strontium-doped mesoporous bioactive glass(Sr-MBG)was prepared by the combination of sol-gel and organic template dodecylamine(DDA),which has good biomineralization activity in vitro.In addition,by loading interferon protein γ(IFN-γ),an immunomodulatory mesoporous bioactive glass IFN-γ@Sr-MBG with sequential polarization of macrophages was constructed.Through the "sequential double release" strategy of IFN-γ and Sr ions,the difference in the timing of IFN-γ and Sr release was used to realize the sequential polarization of macrophages from M0→M1→M2 by the immunomodulatory mesoporous bioactive glass,and to reconstruct the immune microenvironment,thus promoting endothelial cells into blood vessels and stem cells into bone,and finally achieving bone regeneration.Finally,it was further verified by in situ bone defect repair experiments in rats that IFN-γ@Sr-MBG could significantly promote new bone regeneration at the site of bone defects.In summary,the studies in this thesis show that a controlled regulation of macrophage polarization phenotype can be achieved based on a dual release strategy of bioactive ions and anti-inflammatory drugs or proteins.In the initial stage of macrophage immune regulation,activation of the M0 to M1 phenotype of macrophages helps to initiate the inflammatory response and trigger the subsequent series of tissue healing,repair,and regeneration processes;when the inflammatory response is turned on,the M1 phenotype is timely and appropriately changed to the M2 phenotype,which stimulates macrophages to secrete boneenabling factors and creates an immune microenvironment conducive to osteogenic differentiation,thus promoting rapid bone tissue injury site Healing.This thesis provides a new strategy for controlled macrophage polarization for tissue repair.