The Biocompatibility Of Bacterial Cellulose And Its Osteogenesis Loaded With Bone Morphogenetic Protein-2

Part Ⅰ: Study on biocompatibility of nano-bacterial cellulose in vitroObjective: To investigate the biocompatibility of the natural polymer bacterialcellulose in vitro.Methods: Bacterial cellulose was prepared from the bacteria which grew in theliquid sugar matrix. Different concentrations of C₂C₁₂cells and L₉₂₉cells were culturedwith BC in vitro. The morphology of BC scaffold was observed with a scanningelectron microscope. Effects of BC on cell morphological changes in two kinds of cellswere observed by using phase contrast microscope and cell proliferations weremeasured by CCK-8colorimetry.Results: Scanning electron microscopy showed that bacterial cellulose had orderednano-fiberstructure and three dimensional network structures. C₂C₁₂cells and L₉₂₉cellsshowed fusiform shape treated with the materials in vitro; their morphology did notchange significantly. The results of cell proliferation assay showed that the average cellrelative proliferation rate was≥100%treated with the material. The cytotoxicity gradeof BC scaffolds was zero.Conclusions: Bacterial cellulose has good biocompatibility without cytotoxicity，which is beneficial for cell adhesion and proliferation. BC would become a potentialbiomaterial in tissue engineering on the premise of its excellent performance.Part Ⅱ: The osteogenesis of bacterial cellulose scaffold loaded with bonemorphogenetic protein-2Objective: Bacterial cellulose （BC） is a new type of biological material and hasgood physicochemical properties and biocompatibility. To evaluate bacterial cellulose’spotential application as a material for bone tissue engineering, we assayed the biologicalactivity and osteogenesis of bacterial cellulose loaded with bone morphogeneticprotein-2（BMP₂） in vivo and vitro.Methods: BMP₂was prepared from E. Coli and BC was prepared in a static culture system riched with polysaccharides. BMP₂was loaded on BC with differentconcentrations. To explore the bioactivity of BMP₂on scaffolds, we studied theosteogenesis of C₂C₁₂incubated on BC scaffolds with BMP₂in vitro.In vivo, alkalinephophatase（ALP） activity, tissue staining（HE, Von kossa） histologically and calciumdeposition detection were performed to study osteogenesis of BC scaffolds loadedwith BMP₂in ectopic bone formation model.Results:（1） High purity of the bioactive BMP₂was obtained.（2） The growth anddifferentiation of C₂C₁₂cells were well on the BC scaffolds with BMP₂. Differentconcentrations of BMP₂had different influence of osteogenesis; within a certain range,BMP₂on BC scaffolds showed a dose-dependent increase of ALP activity.（3） In vivoBC was well tolerated by the hosts and no acute inflammation was observed. The datashowed that viable osteoblasts appeared within the matrix of BMP₂/BC scaffold whichinvolved in the osteogenesis. ALP activity in the BMP₂/BC experimental group wassignificantly higher than the one in the BC group. HE staining showed new bone tissuehad formed in the experimental group. Meanwhile, BC scaffolds with highconcentration of BMP₂（H-BMP₂/BC） presented significantly morehaematoxylin-eosin+cells than the low concentration of BMP₂（L-BMP₂/BC） did（p<0.05）.4weeks after implantation, the scaffolds of H-BMP₂/BC and L-BMP₂/BCgroups become bigger and harder meanwhile the scaffolds of BC group become softerand smaller. Von Kossa staining showed that many parts of BMP₂/BC systems had morepositive staining than BC group scaffolds did. By quantifying the calcium deposition oftissue, the percentages of calcified tissue in two BC/BMP₂groups were highersignificantly than the BC group, respectively （p<0.01）. Meanwhile there was astatistically significance between H-BMP₂/BC and L-BMP₂/BC systems （p<0.05）.Conclusions: BC’s nanofiber structure can be beneficial for cell adhesion andgrowth because its good biocompatibility and physicochemical properties. A BCscaffold based BMP₂targeting bone repair system was developed. It can be applied as apotential biomaterial in bone tissue engineering with good biological activity.