Human mesenchymal stem cells (hMSCs) have great potential as cell sources for bone tissue engineering and regeneration, but the control and induction of their specific differentiation into bone cells remain challenging. Graphene-based nanomaterials are considered attractive candidates for biomedical applications such as scaffolds in tissue engineering, substrates for SC differentiation and components of implantable devices, due to their biocompatible and bioactive properties. Despite the potential biomedical applications of graphene and its derivatives, only limited information is available regarding their osteogenic activity. This study concentrates upon the effects of reduced graphene oxide (rGO)-coated hydroxyapatite (HAp) composites on osteogenic differentiation of hMSCs. The average particle sizes of HAp and rGO were 1270 ± 476 nm and 438 ± 180 nm, respectively. When coated on HAp particulates, rGO synergistically enhanced spontaneous osteogenic differentiation of hMSCs, without hampering their proliferation. This result was confirmed by determining alkaline phosphatase activity and mineralization of calcium and phosphate as early and late stage markers of osteogenic differentiation. It is suggested that rGO-coated HAp composites can be effectively utilized as dental and orthopedic bone fillers since these graphene-based particulate materials have potent effects on stimulating the spontaneous differentiation of MSCs and show superior bioactivity and osteoinductive potential.

Recently, graphene-based nanomaterials, in the form of two dimensional substrates or three dimensional foams, have attracted considerable attention as bioactive scaffolds to promote the differentiation of various stem cells towards specific lineages. On the other hand, the potential advantages of using graphene-based hybrid composites directly as factors inducing cellular differentiation as well as tissue regeneration are unclear. This study examined whether nanocomposites of reduced graphene oxide (rGO) and hydroxyapatite (HAp) (rGO/HAp NCs) could enhance the osteogenesis of MC3T3-E1 preosteoblasts and promote new bone formation. When combined with HAp, rGO synergistically promoted the spontaneous osteodifferentiation of MC3T3-E1 cells without hindering their proliferation. This enhanced osteogenesis was corroborated from determination of alkaline phosphatase activity as early stage markers of osteodifferentiation and mineralization of calcium and phosphate as late stage markers. Immunoblot analysis showed that rGO/HAp NCs increase the expression levels of osteopontin and osteocalcin significantly. Furthermore, rGO/HAp grafts were found to significantly enhance new bone formation in full-thickness calvarial defects without inflammatory responses. These results suggest that rGO/HAp NCs can be exploited to craft a range of strategies for the development of novel dental and orthopedic bone grafts to accelerate bone regeneration because these graphene-based composite materials have potentials to stimulate osteogenesis.

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In this study, hyaluronic acid (HA)/poly(lactic-co-glycolic acid, PLGA) core/shell fiber meshes loaded with epigallocatechin-3-O-gallate (EGCG) (HA/PLGA-E) for application to tissue engineering scaffolds for skin regeneration were prepared via coaxial electrospinning. Physicochemical properties of HA/PLGA-E core/shell fiber meshes were characterized by SEM, Raman spectroscopy, contact angle, EGCG release profiling and in vitro degradation. Biomechanical properties of HA/PLGA-E meshes were also investigated by a tensile strength test. SEM images showed that HA/PLGA-E fiber meshes had a three-dimensional interconnected pore structure with an average fiber diameter of about 1270 nm. Raman spectra revealed that EGCG was uniformly dispersed in the PLGA shell of meshes. HA/PLGA-E meshes showed sustained EGCG release patterns by controlled diffusion and PLGA degradation over 4 weeks. EGCG loading did not adversely affect the tensile strength and elastic modulus of HA/PLGA meshes, while increased their hydrophilicity and surface energy. Attachment of human dermal fibroblasts on HA/PLGA-E meshes was appreciably increased and their proliferation was steadily retained during the culture period. These results suggest that HA/PLGA-E core/shell fiber meshes can be potentially used as scaffolds supporting skin regeneration.

Osteoprogenitor cells play a significant role in the growth or repair of bones, and have great potential as cell sources for regenerative medicine and bone tissue engineering, but control of their specific differentiation into bone cells remains a challenge. Graphene-based nanomaterials are attractive candidates for biomedical applications as substrates for stem cell (SC) differentiation, scaffolds in tissue engineering, and components of implant devices owing to their biocompatible, transferable and implantable properties. This study examined the enhanced osteogenic differentiation of human mesenchymal stem cells (hMSCs) by reduced graphene oxide (rGO) nanoparticles (NPs), and rGO NPs was prepared by reducing graphene oxide (GO) with a hydrazine treatment followed by annealing in argon and hydrogen. The cytotoxicity profile of each particle was examined using a water-soluble tetrazolium-8 (WST-8) assay. At different time-points, a WST-8 assay, alkaline phosphatase (ALP) activity assay and alizarin red S (ARS) staining were used to determine the effects of rGO NPs on proliferation, differentiation and mineralization, respectively. The results suggest that graphene-based materials have potential as a platform for stem cells culture and biomedical applications.

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In the present study, bifunctional silica-coated Y 2 O 3 :Eu 3+ ,Co 2+ spherical-shaped submicron composite particles were successfully prepared using a facile urea-assisted homogenous precipitation method. Synthesized Y 2 O 3 :Eu 3+ ,Co 2+ phosphor composites showed both ferromagnetic behaviour and strong visible red luminescence emission. The surface of the Y 2 O 3 :Eu 3+ ,Co 2+ phosphor composites was modified with a thin silica layer to enhance the luminescent properties and obtain higher biocompatibility of the samples. The composite particles with silica coatings resulted in a small decrease in the viability of L-929 fibroblastic cells at concentrations lower than 25 ppm and allowed cell imaging via internalization and wide distribution into the cells. Overall, these synthesized novel SiO 2 @Y 2 O 3 :Eu 3+ ,Co 2+ core-shell phosphor composites with both magnetic and luminescent properties have potential biomedical applications, including bioimaging and diagnosis, and can be also potentially used as MRI contrast agents.

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