Novel Reduced Graphene Oxide/Zinc Silicate/Calcium Silicate Electroconductive Biocomposite for Stimulating Osteoporotic Bone Regeneration

In the absence of external assistance, autogenous healing of bone fracture is difficult due to impaired regeneration ability under osteoporosis pathological conditions. In this study, a reduced graphene oxide/zinc silicate/calcium silicate (RGO/ZS/CS) conductive biocomposite with an optimal surface electroconductivity of 5625 S/m was prepared by a two-step spin-coating method. The presence of lamellar apatite nanocrystals on the surfaces of the biocomposite suggests that it has good in vitro biomineralization ability. The silicon and zinc released from the biocomposite induced a significant increase in the osteogenesis of mouse bone mesenchymal stem cells (mBMSCs). Furthermore, alkaline phosphatase activities were further promoted when 3 μA direct current was applied to stimulate the mBMSCs that were cultured on the RGO/ZS/CS surface. However, electrical stimulation failed to further upregulate the osteogenesis-related gene expression. Moreover, RGO/ZS/CS extracts were found to suppress the receptor activator of nuclear factor-κB ligand-induced osteoclastic differentiation of mouse leukemic monocyte macrophages (RAW264.7 cells). Although the zinc ions in the RGO/ZS/CS extracts showed an inhibitory role in human umbilical vein endothelial cell (HUVEC) proliferation, dilutions of the RGO/ZS/CS extracts (1/16, 1/32, and 1/64) promoted HUVEC proliferation, and their angiogenesis-related gene expression was also upregulated. On the basis of the results of the in vitro angiogenesis model, more interconnected tubes formed when the above dilutions of RGO/ZS/CS extracts were added to ECMatrix. The new RGO/ZS/CS electroconductive biocomposite has potential to be used for stimulating osteoporotic bone regeneration.