The development of materials and strategies that can influence stem cell attachment, proliferation, and differentiation towards osteoblasts is of high interest to promote faster healing and reconstructions of large bone defects. Graphene and its derivatives (graphene oxide and reduced graphene oxide) have received increasing attention for biomedical applications as they present remarkable properties such as high surface area, high mechanical strength, and ease of functionalization. These biocompatible carbon-based materials can induce and sustain stem cell growth and differentiation into various lineages. Furthermore, graphene has the ability to promote and enhance osteogenic differentiation making it an interesting material for bone regeneration research. This paper will review the important advances in the ability of graphene and its related forms to induce stem cells differentiation into osteogenic lineages.

A photocrosslinkable gelatin methacryloyl (GelMA) hydrogel has been widely examined in regenerative engineering because of its good cell–tissue affinity and degradability in the presence of matrix metalloproteinases. A halloysite aluminosilicate nanotube (HNT) is a known reservoir for the loading and sustained delivery of therapeutics. Here, we formulate injectable chlorhexidine (CHX)-loaded nanotube-modified GelMA hydrogel that is cytocompatible and biodegradable and provides sustained release of CHX for infection ablation while displaying good biocompatibility. The effects of HNTs and CHX on hydrogel degradability and mechanical properties, as well as on the kinetics of CHX release, and on the antimicrobial efficacy against oral pathogens were systematically assessed. Cytocompatibility in stem cells from human exfoliated deciduous teeth and inflammatory response in vivo using a subcutaneous rat model were determined. Our hydrogel system, that is, (CHX)-loaded nanotube-modified GelMA showed minimum localized inflammatory responses, supporting its ability for drug delivery applications. Moreover, we showed that the incorporation of CHX-loaded nanotubes reduces the mechanical properties, increases the swelling ratio, and diminishes the degradation rate of the hydrogels. Importantly, the presence of CHX-loaded nanotubes inhibits bacterial growth with minimal cell toxicity. Our findings provide a new strategy to modify GelMA hydrogel with chlorhexidine-loaded nanotubes for clinical use as an injectable drug delivery strategy for dental infection ablation.

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Bioprinting, a promising field in regenerative medicine, holds great potential to create three-dimensional, defect-specific vascularized bones with tremendous opportunities to address unmet craniomaxillofacial reconstructive challenges. A cytocompatible bioink is a critical prerequisite to successfully regenerate functional bone tissue. Synthetic self-assembling peptides have a nanofibrous structure resembling the native extracellular matrix (ECM), making them an excellent bioink component. Amorphous magnesium phosphates (AMPs) have shown greater levels of resorption while maintaining high biocompatibility, osteoinductivity, and low inflammatory response, as compared to their calcium phosphate counterparts. Here, we have established a novel bioink formulation (ECM/AMP) that combines an ECM-based hydrogel containing 2% octapeptide FEFEFKFK and 98% water with AMP particles to realize high cell function with desirable bioprintability. We analyzed the osteogenic differentiation of dental pulp stem cells (DPSCs) encapsulated in the bioink, as well as in vivo bone regeneration, to define the potential of the formulated bioink as a growth factor-free bone-forming strategy. Cell-laden AMP-modified bioprinted constructs showed an improved cell morphology but similar cell viability (∼90%) compared to their AMP-free counterpart. In functional assays, the cell-laden bioprinted constructs modified with AMP exhibited a high level of mineralization and osteogenic gene expression without the use of growth factors, thus suggesting that the presence of AMP-triggered DPSCs’ osteogenic differentiation. Cell-free ECM-based bioprinted constructs were implanted in vivo. In comparison with the ECM group, bone volume per total volume for ECM/1.0AMP was approximately 1.7- and 1.4-fold higher at 4 and 8 weeks, respectively. Further, a significant increase in the bone density was observed in ECM/1.0AMP from 4 to 8 weeks. These results demonstrate that the presence of AMP in the bioink significantly increased bone formation, thus showing promise for in situ bioprinting strategies. We foresee significant potential in translating this innovative bioink toward the regeneration of patient-specific bone tissue for regenerative dentistry.