The aim of this study was to investigate whether a surface coating with graphene could enhance the surface bioactivation of titanium alloys (Ti6Al4V) to further accelerate in vivo osteogenesis and osseointegration at the implant surface. In this study, a New Zealand white rabbit femoral condyle defect model was established. After 4, 12 and 24 weeks, biomechanical testing, micro-computed tomography (Micro-CT) analyses and histological observations were performed. At the highest push-out forces during the test, microstructure parameters, such as the bone volume/total volume fraction (BV/TV) and mineral apposition rate (MAR), of the new bone were significantly higher in the graphene-coated Ti6Al4V group (G-Ti6Al4V) than in the Ti6Al4V group (P < 0.05). Van Gieson (VG) staining showed that the G-Ti6Al4V group had more new bone formation than the Ti6Al4V group, and the G-Ti6Al4V group showed a closer fit between the bone and implant. In conclusion, graphene might be a novel type of nano-coating material for enhancing the surface biological activity of Ti-based alloy materials and may further promote in vivo osteogenesis and osseointegration.

In recent years, graphene (G) and graphene oxide (GO) nanoparticles have begun to be applied in surgical implant surface modification. However, biosafety and antibacterial ability of G and GO are still unclear. In this study, the biosafety of G and GO in vitro was evaluated by co-culture with bone marrow mesenchymal stem cells (BMSCs) and biosafety in vivo was observed by implanting materials into mice muscle tissue. Biosafety results showed that 10 μg/ml was the safety critical concentration for G and GO. When the concentration was more than 10 μg/ml, the cytotoxicity of G and GO showed a dose-dependent manner.Antibacterial results showed that G presented the antibacterial ability with the concentration equal to and more than 100 μg/ml; GO presented the antibacterial ability with the concentration equal to and more than 50 μg/ml. The antibacterial effect of G and GO were in a dose-dependent manner in vitro.The GO or G concentration between 50 and 100 μg/ml may be the better range to keep the balance of cytotoxicity and antibacterial ability. Our study reveals that G and GO have potential to be used in clinic with good biosafety and antibacterial properties in a certain concentration range.

The objective of this study was to investigate whether surface coating with graphene could enhance the surface bioactivation of PET-based artificial ligaments to accelerate graft-to-bone healing after anterior cruciate ligament reconstruction. In an in vitro study, the proliferation of MC3T3-E1 cells and their differentiation on the scaffolds were quantified via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and real-time polymerase chain reaction assays. The significantly higher optical-density values and transcription levels of osteoblast-specific genes indicated that graphene modification could promote the proliferation of MC3T3-E1 cells and accelerate their specific differentiation into osteogenic lineages on scaffolds. In an in vivo test, rabbits were used to establish an extra-articular graft-to-bone healing model. At 4, 8, and 12 weeks after surgery, biomechanical tests, microcomputed tomography analysis, and histological observations were performed. The final results demonstrated that the microstructural parameters, the average mineral apposition rate of the bone, and the biomechanical properties of the graphene-coated polyethylene terephthalate (PET)-based artificial ligament (G-PET-AL) group were significantly higher than those of the PET-AL graft group (P < 0.05). The results of Van Gieson staining indicated that in the G-PET-AL group, there was more newly formed bone than there was in the group in which nongraphene-coated PET-ALs were used. In conclusion, graphene exhibits considerable potential for enhancing the surface bioactivation of materials.