Research On Porous Bone Scaffolds Of Bacterial Cellulose/Silk Fibroin /β-TCP

Objective The structure,mechanical property and other physicochemical properties of bacterial cellulose(BC)/silk fibroin(SF)/β-TCP porous bone scaffolds with different contents of submicron β-TCP were tested,as well as the biological compatibility.The immunoregulatory effects of porous scaffolds on mouse mononuclear macrophage leukemia cells(RAW264.7)were investigated with in vitro co-culture.The regulatory effects of submicron β-TCP on mouse RAW264.7 and its osteogenesis effects on bone marrow mesenchymal stem cells in SD rats were also investigated.Methods The freeze-drying method was used to construct BC/SF/β-TCP porous bone scaffolds with different contents of β-TCP.Firstly,The bacterial cellulose solution and silk fibroin solution were evenly mixed,and their mass ratio was maintained at 20/3.On this basis,Submicron β-TCP powder was added and dispersed evenly(The concentration of β-TCP in the mixture was 0mg/m L,50mg/m L,100mg/m L and 150mg/m L,namely BC/SF,BC/SF/5%β-TCP,BC/SF/10%β-TCP and BC/SF/15%β-TCP respectively after freeze drying).SEM,XRD,Universal testing machine and other methods were used to test the microstructure,mechanical property,water-uptake,expansibility and other physicochemical properties of the porous bone scaffolds.CCK-8 and Live/ Dead experiments were used to observe the cellular compatibility of bone scaffolds.Inflammatory response of the porous bone scaffolds was studied by back subcutaneous implantation in SD rats.Porous scaffolds co-cultured with RAW264.7 in vitro in order to evaluate its bone immune regulation effect.Submicron β-TCP interfered with RAW264.7 to evaluate its effect of bone immune regulation and bone mesenchymal stem cells to evaluate its osteogenic ability respectively.Results Among the four kinds of porous scaffolds,the porosity,water-uptake and expansibility gradually decreased and the mechanical property were increased with the augment of β-TCP contents,while the porosity of the scaffolds was gradually decreased.The experiments of CCK8 and Live/Dead showed that the porous scaffolds had good cellular compatibility and did not cause serious inflammatory reactions after subcutaneous implantation in SD rats.BC/SF/15%β-TCP could promote the maximum polarization of RAW264.7 to M2 type,which could also accelerate the secretion of osteogenesis factors as well as angiogenic factors.Submicron β-TCP could promote the polarization of RAW264.7 to M1 and M2 type and the secretion of immune regulatory factors;When β-TCP interfered with bone marrow mesenchymal stem cells in SD rats at different concentrations,150mg/m L concentration of β-TCP powder was more effective in promoting bone formation.Conclusion BC/SF/β-TCP porous bone scaffolds prepared by freeze-drying method have good physicochemical properties and biocompatibility,Moreover,which can regulate the polarization of macrophages and has immunomodulatory effects.Submicron β-TCP has the ability of regulating bone immunity and promoting osteogenic differentiation of bone marrow mesenchymal stem cells in SD rats.