Seok-Jae Kim

Sequential delivery of BMP-2 and BMP-7 for bone regeneration using a heparinized collagen membrane.

To investigate the effect of the sequential delivery of bone morphogenetic proteins BMP-2 and BMP-7 on bone regeneration in rat calvarial defects (40 Sprague-Dawley rats, 8mm defect size), all animals were treated with a hydroxyapatite (HA)/tricalcium phosphate (TCP) bone graft covered with a collagen membrane. The experimental groups were as follows: (1) control group: unmodified collagen (no treatment); (2) BMP-2 group: 5 μg of BMP-2; (3) hep-BMP-7 group: 5 μg BMP-7 chemically bound to heparinized collagen; and (4) BMP-2/hep-BMP-7 group: 2.5 μg BMP-7 bound to heparinized collagen and subsequently treated with 2.5 μg BMP-2. Defect healing was examined at 2 and 8 weeks after surgery. The BMP-2 group showed the largest new bone area at week 2 (29.3 ± 7.3%; P = 0.009); new bone areas in the hep-BMP-7 and BMP-2/hep-BMP-7 groups were similar (11.8 ± 3.4% and 12.9 ± 5.71%, respectively; P = 0.917). After 8 weeks, the BMP-2/hep-BMP-7 group showed the largest new bone area (43.3 ± 6.2%), followed by the BMP-2 and hep-BMP-7 groups (P = 0.013). Accordingly, in comparison with single deliveries of BMP-2 and BMP-7, sequential delivery of BMP-2 and BMP-7 using a heparinized collagen membrane significantly induced new bone formation with a smaller quantity of BMP-2 in rat calvarial defects.

Fabrication and Characterization of Reduced Graphene Oxide Counter Electrode for Dye-Sensitized Solar Cells

To improve performance of dye-sensitized solar cell(DSSC), thermally reduced graphene oxide(rGO) was investigated as Pt-free counter electrodes(CE) material. The DSSCs with rGO were fabrcated by simple spin coating method under different temperature and ambient atmospheres like Ar, N2 and air. When the rGO CE was reduced at 450°C under the Ar atmosphere, it was obtained the power conversion efficiency of 6.02%, which showed the high catalytic activity and performance of DSSC as much as Pt. This value means the thermally reduced rGO CEs under the Ar gas will be suitable as a substitute for Pt CEs.

Graphene/Polyaniline Nanocomposite Multilayer Counter Electrode by Inserted Polyaniline of Dye-Sensitized Solar Cells

Polyaniline (PANI) conducting polymer and graphene are preferred counter electrode (CE) materials for dye-sensitized solar cells (DSSC). Graphene/PANI nanocomposite multilayer CE is created through the insertion of a PANI layer. It has been demonstrated as a platinum-free counter electrode for cost-efficient DSSCs. Here, graphene/PANI nanocomposite and PANI were synthesized by electro-polymerization from a solution containing aniline monomers and graphene. Graphene/PANI nanocomposite multilayer CE showed improved electrical conductivity, interface charge transfer rate, and catalytic activity on I3− reduction compared with the Pt CE. The high electro-catalytic ability of graphene/PANI nanocomposite multilayer CE was demonstrated by cyclic voltammetry and electrochemical impedance spectroscopy.

Characterization of ZnO-Graphene electron transfer layer co-deposited by cyclic voltammetry for inverted organic solar cells

ABSTRACT Non-reduction graphene oxide was stirred with ZnCl2:NaCl electrolyte, and then electrochemically co-deposited by cyclic voltammetry to simplify manufacturing electron transfer layer(ETL) for inverted organic solar cells. The morphology and chemical characteristic of the ETL were measured by scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS) and Raman spectroscopy. C-C, C1 bonds were detected in XPS. ZnO, graphene peak were detected in Raman spectroscopy. Result of J-V characteristic, when concentration of the graphene oxide in the electrolyte at 0.03 wt% was showed the highest photoelectric conversion efficiency(PCE) of 1.109% which is 34% higher than 0.824% PCE of ZnO ETL devices.

Fabrication and biological properties of calcium phosphate/chitosan composite coating on titanium in modified SBF

In order to increase the biocompatibility and bioactivity of chitosan, hydroxyapatite was in situ combined into the spin-coated chitosan layer on the titanium substrate by incubating in modified simulated body fluid (m-SBF). The calcium phosphate/chitosan (CaP/CS) composite prepared in m-SBF showed a homogeneous distribution of spherical nano-clusters. The hydrophilicity of the coatings was increased by performing NaOH post-treatment of CaP/CS composites, which also affected apatite formation. Biocompatibility of the coatings was assessed by investigating the cellular response of human osteoblast-like MG-63 cells with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell adhesion and osteogenic properties of the mesoporous CaP/CS composite were evaluated by SEM and ALPase assay, respectively. This in vitro study showed improved cell adhesion and differentiation on nanostructured CaP/CS composites. These results indicate that this CaP/CS composite could be a promising candidate for bone tissue engineering.

Phenanthroline-based ruthenium complexes for enhanced charge transportation in solvent-free ionic liquid electrolyte

In the present work, we synthesized a series of 1,10-phenanthroline-based ruthenium complexes (PRCs). The PRCs were characterized by 1H and 13C NMR, UV–Vis and fluorescence spectroscopic analyses. Further, we used these PRCs complexes as effective additives in ionic liquid (IL) electrolyte to enhance current conduction in electrochemical cells. Anodic peak current in cyclic voltammetry response of PRCs showed functional group dependence on the nature of ruthenium complex. Mono-propenyl-functionalized PRC additive in IL electrolyte exhibited relatively higher current density, lower charge transfer resistance and decreased impedance compared to the tri-propenyl-functionalized PRC as well as without functional groups on 1,10-phenanthroline ligand in Ru complex. Finally, the PRCs as additives in IL electrolyte were tested in dye-sensitized solar cell which showed an increase of 65% in the efficiency when mono-propenyl-functionalized PRC complex was used as an additive.

The effect of tourmaline additives in TiO2 photoanode for high-efficiency dye sensitized solar cells

ABSTRACT Tourmaline is a kind of borosilicatemineral and has spontaneous polarization property. Due to this property, it can generate a feeble current around 0.06 mA[1]. We fabricated the TiO2 photoanode with different wt.% ratio of tourmaline and investigated the effect of tourmaline additive on dye sensitized solar cells (DSSCs). We carried out electrochemical impedance spectroscopy (EIS) and current density-voltage (J-V) measurement. The results showed that the electron lifetime and the power conversion efficiency of the DSSCs with TiO2 photoanode containing 3wt% tourmaline were enhanced by about 42% and 20%, respectively, as compared to the DSSCs using pristine TiO2 photoanode.