Abstract:

Objective To explore the spatial support capacity and its influence in osteogenic effect of composite biofilm based on poly（propylene carbonate） （PPC） /poly（butylene succinate） （PBS） in rabbit tibial bone defect models， and to clarify its barrier functional reliability and osteogenetic effect in vivo. Methods The composite biofilms of PPC/PBS and PPC/PBS/collegen type Ⅰ （Col-Ⅰ）（PPC/PBS/Co） were prepared.Eighteen Japanese big-ear rabbits were selected and two bone defects were prepared on each side of the tibia of the rabbits. Six rabbits were randomly selected to place PPC/PBS composite biofilm on the bone defects， 2 rabbits were executed at 2， 4， 8 and 12 weeks after operation， and the surface microstructures of PPC/PBS composite biofilm in the rabhit bone defect area were observed by scanning electron microscope （SEM）. The experiment was divided into blank control group， PPC/PBS composite biofilm group， BME-10X collagen membrane group， and PPC/PBS/Co composite biofilm group. The above biofilms were placed on the corresponding bone defects of rabbits by operation， while no biofilm was placed in the rabbits in blank control group. Three rabbits were killed at 2， 4， 8 and 12 weeks after operation respectively， and the gray values of regenerated bone in the bone defect areas of the rabbits in varrous groups were detected by soft X-ray； the fluorescence intensities of regenerated bone tissue in the bone defect areas of the rabbits in various groups were observed by laser scanning confocal microscope after fluorescence labeling. The pathomorphology of regenerated bone tissue in the bone defect areas of the rabbits in various groups were observed by HE staining and modified Gomori staining， and the expression levels of bone morphogenetic protein 2 （BMP-2） and osteopontin （OPN） in the regenerated bone tissue in bone defect areas of the rabbits in various groups were detected by immunohistochemical staining. Results In general， the PPC/PBS composite biofilm was tightly covered in the bone defect area without displacement and collapse. The SEM results showed that the porous surface of PPC/PBS composite biofilm appeared micropore structure and the number of micropores was increased with the prolongation of time， while the smooth surface of biofilm basically did not form the micropore-like structure. The results of soft X-ray detection showed that the gray values of regenerated bone tissue in bone defect areas of the rabbits in various groups were increased with the prolongation of time， and the gray value of regenerated bone tissue in bone defect areas of the rabbits in PPC/PBS/Co composite biofilm group was significantly higher than those in other groups （P<0.05）. The confocal micrscope results showed that the fluorescence intensity of regenerated bone tissue in bone defect areas of the rabbits in PPC/PBS/Co composite biofilm group was similar to those in blank control group at 4， 8， and 12 weeks； compared with PPC/PBS composite biofilm group and BME-10X collagen membrane group， the fluoresence intensity of regenerated bone tissue in bone defect areas of the rabbits in PPC/PB/Co composite biofilm group at 4 weeks was increased （P<0.05）， and the fluoresence intensity of regenerated bone tissue in bone defect areas of the rabbits at 8 and 12 weeks were decreased （P<0.05）. The results of HE staining and modified Gomori staining showed that compared with PPC/PBS composite biofilm group and BME-10X collagen membrane group， the new bone formed faster in PPC/PBS/Co composite biofilm group and blank control group at 2 and 4 weeks， and the lamellar bone mineralization was higher at 12 weeks. The immunohistochemical staining results showed that compared with blank control group， PPC/PBS composite biofilm group and BME-10X collagen membrane group， the expression levels of BMP-2 and OPN proteins in the regenerated bone tissue in bone defect areas of the rabbits in PPC/PBS/Co composite biofilm group at 2 and 4 weeks were increased （P<0.05 or P<0.01）； compared with blank control group and PPC/PBS composite biofilm group， the expression levels of BMP-2 and OPN proteins in the regenerated bone tissue in bone defect areas of the rabbits in BME-10X collage membrane group were decreased （P<0.05 or P<0.01）. Conclusion PPC/PBS composite biofilm has excellent spatial support capacity and reliable physical barrier function. The PPC/PBS/Co composite biofilm has a good effect in guiding bone regeneration in vivo.

Key words: Guided bone regeneration, Composite biofilm, Poly（propylene carbonate）, Poly（butylene succinate）, Bone defect