Evaluation of the osteogenesis and osseointegration of titanium alloys coated with graphene: an in vivo study.

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.

Biosafety and Antibacterial Ability of Graphene and Graphene Oxide In Vitro and In Vivo.

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.

Synergistic Effect of Mesoporous Silica and Hydroxyapatite in Loaded Poly(DL-lactic-co-glycolic acid) Microspheres on the Regeneration of Bone Defects.

A microsphere composite made of poly(DL-lactic-co-glycolic acid) (PLGA), mesoporous silica nanoparticle (MSN), and nanohydroxyapatite (nHA) (PLGA-MSN/nHA) was prepared and evaluated as bone tissue engineering materials. The objective of this study was to investigate the synergistic effect of MSN/nHA on biocompatibility as well as its potential ability for bone formation. First, we found that this PLGA-MSN/nHA composite performed good characteristics on microstructure, mechanical strength, and wettability. By cell culture experiments, the adhesion and proliferation rate of the cells seeded on PLGA-MSN/nHA composite was higher than those of the controls and high levels of osteogenetic factors such as ALP and Runx-2 were detected by reverse transcriptase polymerase chain reaction. Finally, this PLGA-MSN/nHA composite was implanted into the femur bone defect in a rabbit model, and its ability to induce bone regeneration was observed by histological examinations. Twelve weeks after implantation, the bone defects had significantly more formation of mature bone and less residual materials than in the controls. These results demonstrate that this PLGA-MSN/nHA composite, introducing both MSN and nHA into PLGA microspheres, can improve the biocompatibility and osteoinductivity of composite in vitro and in vivo and had potential application in bone regeneration.

Effects of Artificial Ligaments with Different Porous Structures on the Migration of BMSCs.

Polyethylene terephthalate- (PET-) based artificial ligaments (PET-ALs) are commonly used in anterior cruciate ligament (ACL) reconstruction surgery. The effects of different porous structures on the migration of bone marrow mesenchymal stem cells (BMSCs) on artificial ligaments and the underlying mechanisms are unclear. In this study, a cell migration model was utilized to observe the migration of BMSCs on PET-ALs with different porous structures. A rabbit extra-articular graft-to-bone healing model was applied to investigate the in vivo effects of four types of PET-ALs, and a mechanical test and histological observation were performed at 4 weeks and 12 weeks. The BMSC migration area of the 5A group was significantly larger than that of the other three groups. The migration of BMSCs in the 5A group was abolished by blocking the RhoA/ROCK signaling pathway with Y27632. The in vivo study demonstrated that implantation of 5A significantly improved osseointegration. Our study explicitly demonstrates that the migration ability of BMSCs can be regulated by varying the porous structures of the artificial ligaments and suggests that this regulation is related to the RhoA/ROCK signaling pathway. Artificial ligaments prepared using a proper knitting method and line density may exhibit improved biocompatibility and clinical performance.

Effects of graphene modification on the bioactivation of polyethylene-terephthalate-based artificial ligaments.

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.