Preparation And Performance Of An IFN-γ-loaded Strontium Micro-nano Bioactive Glass/PLGA Scaffold For Osteoimmunomodulation

The bone immune response dominated by macrophages,who plays an important role in the osteogenesis process of bone defect repair.Macrophages can be named as pro-inflammatory M1 phenotype and anti-inflammatory M2 phenotype according to Th1/Th2 targeting helper T cells.It is generally recognized that M2 macrophages are more closely related to the later stage of tissue repair,and they will contribute bone morphogenetic factors and osteogenesis-related factors to promote osteogenesis in the process of osteogenesis.However,recent studies have confirmed that M1 also plays an important role in early angiogenesis,osteointegration.Moreover,after biomaterials are implanted in the body,the premature conversion of macrophages to M2 type will cause them to secrete too much fibrous factors,forming a fibrous capsule to wrap the implant and cause implantation failure;too late conversion to M2 phenotype will lead to delayed scar tissue or wound healing.Therefore,realizing the timely conversion of macrophages from M1 phenotype to M2 phenotype may be more conducive to osteogenesis.In this paper,the research focuses on the effect of macrophage sequence regulation and phenotypic conversion on bone defect repair.SrBG was prepared by combining the sol-gel method and the template method,and the composite scaffold was prepared by blending it with PLGA.By loading a small amount of interferon-γ（IFN-γ）on it,a bone defect implant with multiple functions such as sequential regulation of macrophage polarization and promotion of bone defect repair was prepared.On this basis,we further studied the effect of sequential regulation of macrophage polarization on osteoblast-related cells,and the mechanism of immune regulation affecting bone defect repair.The main research contents and conclusions of this paper are as follows:（1）SrBG was prepared,combined with PLGA and IFN-γ,to prepared a pure PLGA scaffold,SrBG/PLGA composite scaffold and IFN-γ/SrBG bone immune regulation scaffold with IFN-γrespectively;（2）Through ion release experiments,it is verified that the scaffold releases IFN-γin the early stage and continuously releases Sr ions in the later stage;（3）Through in vitro flow cytometry and q-PCR detection and experiments,it is verified that the IFN-γreleased in the early stage promotes the polarization of macrophages to the M1type,and the release of SrBG in the later stage activates the M2 phenotype;（4）Sequential polarization of macrophages was verified to obviously promote osteogenesis in vitro by alizarin red S staining as well as osteogenesis related gene expression assays;（5）The in vivo rat orthotopic bone defect repair experiments printed the experimental results were consistent with those in vitro.Here,a new type of bone immunomodulatory scaffold IFN-γ/Sr-dropped bioactive glass composite scaffolds（IFN-γ/SrBG）were successfully prepared which integrates multiple biological functions at different stages of the bone healing process.The scaffolds can polarize macrophages into pro-inflammatory M1 type at the early stage of implantation by releasing IFN-γwithin the first day,and then polarize macrophages into anti-inflammatory M2 type in later stage by releasing Sr²⁺from SrBG,which promoted mature bone formation in bone defects to a greater extent.Therefore,IFN-γ/SrBG scaffolds are expected to become an excellent bone tissue engineering materials by sequential regulation macrophages polarization.