Oh Seong Jin

Enhanced Osteogenesis by Reduced Graphene Oxide/Hydroxyapatite Nanocomposites

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.

Facile synthesis of bifunctional silica-coated core–shell Y2O3:Eu3+,Co2+ composite particles for biomedical applications

In the present study, bifunctional silica-coated Y2O3:Eu3+,Co2+ spherical-shaped submicron composite particles were successfully prepared using a facile urea-assisted homogenous precipitation method. Synthesized Y2O3:Eu3+,Co2+ phosphor composites showed both ferromagnetic behaviour and strong visible red luminescence emission. The surface of the Y2O3:Eu3+,Co2+ 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 SiO2@Y2O3:Eu3+,Co2+ 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.

Cell imaging and DNA delivery in fibroblastic cells by conjugated polyelectrolytes

This study concentrates on the potential application of conjugated polyelectrolytes (CPEs) to cell imaging and DNA delivery. Four different types of polyfluorene copolymers, namely, PAHFP‐Br, PAEFP‐Br, PAHFbT‐Br, and PSBFP‐Na, which have the same π‐conjugated backbone but different side chains, were synthesized. For cytotoxicity testing, L‐929 fibroblastic cells were treated with increasing concentrations (0–50 µM) of each CPE and then cell viability was determined by WST‐8 assay. Cellular uptake of CPEs into cultured L‐929 cells was observed by fluorescence microscopy. To examine DNA delivery by CPEs, the cells were incubated for 1 H with PAHFP‐Br/fluorescein (Fl)‐labeled single‐stranded DNA (ssDNA‐Fl) complex and then visualized by fluorescence microscopy. Cytotoxicity of CPEs was increased in a dose‐dependent manner but at lower than 10 µM, PAHFP‐Br, PAEFP‐Br, and PSBFP‐Na did not show any cytotoxic effects on the cells. When added to cell cultures at 1 µM, PAHFP‐Br/ssDNA‐Fl complex was delivered and then dissociated into PAHFP‐Br and ssDNA‐Fl within the cells. This result implies that PAHFP‐Br can enable cell imaging and DNA delivery into fibroblastic cells. Therefore, it is suggested that PAHFP‐Br with various advantages such as low cytotoxicity and high fluorescence efficiency can be extensively used as a potential agent for cell imaging and gene delivery.