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We have synthesized binary reduced-graphene-oxide (RGO)/metal-oxide (Ni(OH)2, NiO, MnO2, and Fe3O4) nanocomposites by using a facile hydrothermal process. The morphology and the structure of the composite are confirmed by using x-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), field-emission scanning electron microscopy (FESEM) and Raman spectroscopy. The electric capacitances that have been achieved for the nanocomposites at a current density of 1 A/g are 55, 140, 150 and 183 F/g for RGO/Fe3O4, RGO/Ni(OH)2, RGO/NiO and RGO/MnO2, respectively. Among them, RGO/MnO2 having the best electric capacity was used for preparing a current collector electrode by using various methods to attach the RGO/MnO2 nanocomposite to nickel foams. The supercapacitor performances of differently prepared current collector electrodes were tested, and the electric capacities found with the nanocomposites having a current density of 1 A/g are 28, 53, 112 and 212 F/g when the two-step drop method, the hydrothermal method, the doctor-blade method and the nanocomposite-drop method were used, respectively. Compared to a single metal-oxide, RGO/MnO2 nanocomposites show a superior electric conductivity, an electric capacity and a charge/discharge efficiency for supercapacitor performance, indicating that the RGO/metal-oxide nanocomposite is a promising material for supercapacitor applications.

Currently, applications of graphene and its derivatives have been reported in many fields. In particular, graphene oxide (GO) has been studied for biomedical applications, such as cell imaging, biosensors and drug delivery systems, because of its good biocompatibility and excellent physicochemical properties. Recently, much research has been conducted to control cell behavior, including attachment, proliferation and differentiation by using GO. On the other hand, the effects of GO on myogenic differentiation have not been explored. In the present study, the influence of GO on myogenic differentiation was investigated. This study assessed the cytotoxicity of GO and evaluated the myogenic differentiation of C2C12 murine myoblasts in growth media containing 10 μg/mL of GO. The physicochemical properties of GO were characterized by using atomic force microscopy (AFM) and Raman spectroscopy. The cytotoxicity was evaluated by using a WST-8 assay. An analysis of myogenic differentiation was performed by using immunofluorescence staining for the myosin heavy chain (MHC; myogenic differentiation marker) and was determined by calculating the amount of multinucleate myotube formation, the fusion index and the maturation index. GO did not exhibit cytotoxicity at low concentrations and effectively stimulated the myogenic differentiation of C2C12 murine myoblasts. Therefore, GO has potential skeletal tissue engineering applications.

Extracellular matrices (ECMs) are network structures that play an essential role in regulating cellular growth and differentiation. In this study, novel nanofibrous matrices were fabricated by electrospinning M13 bacteriophage and poly(lactic-co-glycolic acid) (PLGA) and were shown to be structurally and functionally similar to natural ECMs. A genetically-engineered M13 bacteriophage was constructed to display Arg-Gly-Asp (RGD) peptides on its surface. The physicochemical properties of RGD peptide-displaying M13 bacteriophage (RGD-M13 phage)/PLGA nanofibers were characterized by using scanning electron microscopy and Fourier-transform infrared spectroscopy. We used immunofluorescence staining to confirm that M13 bacteriophages were homogenously distributed in RGD-M13 phage/PLGA matrices. Furthermore, RGD-M13 phage/PLGA nanofibrous matrices, having excellent biocompatibility, can enhance the behaviors of vascular smooth muscle cells. This result suggests that RGD-M13 phage/PLGA nanofibrous matrices have potentials to serve as tissue engineering scaffolds.

Neurons are electrically excitable cells that transmit and process information in the nervous system. Recently, the differentiation of human neural stem cells to neurons has been shown to be enhanced on graphene substrates, and differentiated neurons have been shown to be able to still carry electrical signals when stimulated by graphene electrodes. Graphene films grown by using chemical vapor deposition were transferred onto glass coverslips by using the scooping method and were then coated with fetal bovine serum for a neuronal cell culture. The graphene substrates as biomimetic cues have been shown to enhance the neurite outgrowth of PC-12 cells. Our findings suggest that graphene has a unique surface property that can promote neuronal cells, which should open tremendous opportunities in neuroscience, neural engineering and regenerative medicine.

This study concentrates upon investigating differential cellular responses to carbon nanoparticles (CNPs) such as pristine graphene flakes, single-walled carbon nanotubes (SWCNTs) and multiwalled CNTs (MWCNTs), in human dermal fibroblasts (HDFs) vs. the L-929 fibroblast cell line. Characterizing the surface morphology of each CNP by using scanning electron microscopy, we determined their cytotoxicity profiles by quantifying the mitochondrial activity. Graphene was found to have an irregular flake-like shape with various lengths within the ranges of 50 ∼ 1500 nm. The estimated sizes of the SWCNTs and the MWCNTs were about 400 nm and 1000 nm in diameter, respectively and several µm in length. All the CNPs tested here exerted adverse effects on the viability of HDFs even at 15.6 ppm, through intracellular uptake whereas except MWCNTs, they did not show any cytotoxicity against L-929 cells at 250 ppm. This result suggests that CNPs can have a differential influence on normal fibroblasts vs. immortalized ones.