Properties of vaterite-containing tricalcium silicate composited graphene oxide for biomaterials

Size-dependent molecular interaction of nontraditional 2D antibiotics withStaphylococcus aureus

The application of nanomaterials for their antibacterial properties is the subject of many studies due to antibiotic resistance of pathogen bacteria and the necessity of omitting them from food and water resources. Graphene oxide (GO) is one of the most popular candidates for antibacterial application. However, the optimum condition for such an effect is not yet clear for practical purposes. To shed light on how GO and bacteria interaction depends on size, a wide range of GO flake sizes from hundreds of µm²going down to nano-scale as low as 10 N m²was produced. In anin-vitrosystematic study to inhibitStaphylococcus aureusgrowth, the correlation between GO flake size, thickness, functional group density, and antibacterial activity was investigated. The GO suspension with the average size of 0.05 µm², in the order of the size of the bacteria itself, had the best bacteriostatic effect onS. aureuswith the minimum inhibitory concentration value of 8 μg ml^-1, well within the acceptable range for practical use. The bacteriostatic effect was measured to be a 76.2% reduction of the colony count over 2 h of incubation and the mechanism of action was the wrapping and isolation of cells from the growth environment. Furthermore,in-vivoanimal studies revealed that 16 μg ml^-1of the optimum GO has efficient antibacterial performance against the methicillin-resistant strains of the bacteria with an enhanced wound healing rate and tensiometrial parameters which is important for realized targets.

The in vivo dissolution of tricalcium silicate bone cement

This study aimed to investigate the in vivo dissolution of tricalcium silicate (Ca₃ SiO₅ , C₃ S) bone cement in the rabbit femoral defect. Results indicated that C₃ S paste directly integrated with the bone tissue without the protection of the bone-like apatite. Calcium silicate hydrate gel (C-S-H gel) and Ca(OH)₂ were the main components of C₃ S paste. The dissolution model of C₃ S paste was a mass loss rather than a decrease in volume. The initial dissolution of C₃ S paste (0 ~ 6 weeks) was greatly attributed to the release of Ca(OH)₂ , and the later dissolution (>6 weeks) was attributed to the decalcification of C-S-H gel. Although the mass of C₃ S paste could decrease by more than 19 wt % after 6 weeks of implantation, the created pores (<1 μm) were not large enough for the bone tissue to migrate into C₃ S paste. The loss of Ca ions also resulted in the transformation of SiO₄ tetrahedrons from Q¹ and Q² to Q⁰ , Q³ , and Q⁴ in C-S-H gel. Because only isolated SiO₄ tetrahedrons (Q⁰ ) and Ca ions could be absorbed by the bone tissue, C₃ S paste gradually transformed into a silica-rich gel. The fundamental reason for no decrease in volume of C₃ S paste was that the SiO₄ tetrahedron network still maintained the frame structure of C₃ S paste during the implantation.

Applications of Graphene and Its Derivatives in Bone Repair: Advantages for Promoting Bone Formation and Providing Real-Time Detection, Challenges and Future Prospects

During continuous innovation in the preparation, characterization and application of various bone repair materials for several decades, nanomaterials have exhibited many unique advantages. As a kind of representative two-dimensional nanomaterials, graphene and its derivatives (GDs) such as graphene oxide and reduced graphene oxide have shown promising potential for the application in bone repair based on their excellent mechanical properties, electrical conductivity, large specific surface area (SSA) and atomic structure stability. Herein, we reviewed the updated application of them in bone repair in order to present, as comprehensively, as possible, their specific advantages, challenges and current solutions. Firstly, how their advantages have been utilized in bone repair materials with improved bone formation ability was discussed. Especially, the effects of further functionalization or modification were emphasized. Then, the signaling pathways involved in GDs-induced osteogenic differentiation of stem cells and immunomodulatory mechanism of GDs-induced bone regeneration were discussed. On the other hand, their applications as contrast agents in the field of bone repair were summarized. In addition, we also reviewed the progress and related principles of the effects of GDs parameters on cytotoxicity and residues. At last, the future research was prospected.

Preparation and Characterization of Iron-Doped Tricalcium Silicate-Based Bone Cement as a Bone Repair Material

Iron is one of the trace elements required by human body, and its deficiency can lead to abnormal bone metabolism. In this study, the effect of iron ions on the properties of tricalcium silicate bone cement (Fe/C3Ss) was investigated. It effectively solved the problems of high pH value and low biological activity of calcium silicate bone cement. The mechanical properties, in vitro mineralization ability and biocompatibility of the materials were systematically characterized. The results indicate that tricalcium silicate bone cement containing 5 mol% iron displayed good self-setting ability, mechanical properties and biodegradation performance in vitro. Compared with pure calcium silicate bone cement (C3Ss), Fe/C3Ss showed lower pH value (8.80) and higher porosity (45%), which was suitable for subsequent cell growth. Immersion test in vitro also confirmed its good ability to induce hydroxyapatite formation. Furthermore, cell culture experiments performed with Fe/C3Ss ion extracts clearly stated that the material had excellent cell proliferation abilities compared to C3Ss and low toxicity. The findings reveal that iron-doped tricalcium silicate bone cement is a promising bioactive material in bone repair applications.