Preparation Of Reduced Graphene Oxide Surface-modified Calcium Silicate Bioceramic And Its Bone Regeneration Performances

Osteoporosis is a common bone disease that always happens in postmenopausal women and elders.Typically,its symptoms express as impaired bone regeneration ability as well as enhanced bone resorption capacity.Commonly,the osteoporosis patients have high risks of suffering from bone fractures due to their reduced bone mass and diminished bone mineral density.Under the osteoporosis pathological condition,the autogeneous healing capacity is extremely poor without any external assistance.Therefore,for the purpose of improving the regeneration ability of bone tissue around the osteoporosis pathological area,a kind of reduced graphene oxide(rGO)surface-modified calcium silicate(CS)electroconductive bioceramic(rGO/CS)was prepared in this study.Firstly,graphene oxide(GO)was prepared by the modified Hummers method.Afterwards the ascorbic acid(AC)reduction method,the thermal reduction method as well as the combination of these two methods were seperately used to make GO reduced into rGO.The results indicates,by comparing with the AC reduction method or the thermal reduction method,the combination of AC reduction method and thermal reduction method contributes to getting the rGO with less oxygen containing groups as well as high ordered carbon atomic layer.Moreover,the rGO prepared by the combination of AC reduction method and thermal reduction method exhibits optimal conductivity when the annealing temperature is 600?.Different amounts of rGO powders prepared by the AC reduction method were added into the sodium alginate(SA)solutions(3 wt%),and the rGO/SA suspensions with varying concentrations were obtained.Subsequently,the as-prepard rGO/SA suspensions were spin coated on the surface of CS bioceramic tablets,and the rGO/CS bioceramics were successfully obtained after experiencing 2 h of annealing at 600?.The concentration of the rGO/SA suspensions as well as the coating time would greatly affect the final surface electroconductivity of rGO/CS bioceramics.In this study,when 3 mg/mL rGO/SA suspension was spin coated on the CS bioceramic tablet two times,the obtained rGO/CS bioceramics had the optimal surface electroconductivity(5512.63 ± 516.09 S/m).When rGO/CS electroconductive bioceramic were soaked in the simulated body fluids,they still possessed better in vitro biomineralization ability,indicating that the rGO surface layer would not restrict the hydroxyapatite crystals depositing on its surface.When mouse bone mesenchymal stem cells(mBMSCs)were cultured on the rGO/CS electroconductive bioceramics surfaces,and 3 ?A DC was then applied to stimulating them,it was found that the alkaline phosphatase activities of mBMSCs were significantly enhanced.Moreover,osteogenesis related genes(Col-I,OC,Runx2)expression was significantly up-regulated as well,implying that ES could further promoting the in vitro osteogenesis of rGO/CS bioceramics.The rGO/CS extracts were capable of suppressing the differentiation of RANKL-induced mouse leukaemic monocyte macrophages(RAW264.7)into osteoclasts by making the osteoclastogenesis related genes(TRAP,NFATc1,Car2,MMP-9)expression to be down-regulated.Furthermore,silicon released from the rGO/CS bioceramics not only could promote the proliferation of human umbilical vein endothelial cells(HUVECs),but also enhance the migration ability of HUVECs,and thereby resulted in the improvement of the in vitro angiogenesis.In summary,the rGO/CS electroconductive bioceramics prepared in this study are promising to be applied to assisting bone regeneration under the osteoporosis pathological condition.