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Hong Jang,Min Soo KIM,Woongsik Jang,Hyungbin Son,Dong Hwan Wang,Felix Sunjoo Kim 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.86 No.-
We demonstrated a simple and effective processing protocol to improve the electrical conductivity ofpoly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)films via post-treatment withan alcohol-based solvent, 2-chloroethanol (2-CE), and to enhance their performance as a transparentanode in organic photovoltaic cells (OPVs). Owing to its moderate boiling point, in contrast to previouslyreported chemicals, 2-CE is advantageous both for handling as a liquid-phase chemical and for dryingfrom thefilms via evaporation. We compared the optical and electrical properties of the 2-CE-treatedPEDOT:PSS with those of standard PEDOT:PSS-based electrodes with the addition of 5 vol% dimethylsulfoxide (DMSO). With a similar thickness and transmittance in the visible region, the 2-CE-treatedpolymer electrodes outperformed the DMSO-addedfilms with regard to the electrical conductivity (762S cm 1 vs. 439 S cm 1). The work functions were almost identical:5 eV. We fabricated and characterizedorganic photovoltaic devices using the anodes and polymer:fullerene blends and found that the 2-CEtreatment resulted in higher device performance. Additionally, the 2-CE treatment was applicable toOPVs on aflexible plastic substrate, indicating the effectiveness of the proposed protocol.
Suhito, Intan Rosalina,Han, Yoojoong,Min, Junhong,Son, Hyungbin,Kim, Tae-Hyung Elsevier 2018 Biomaterials Vol.154 No.-
<P><B>Abstract</B></P> <P>Precise characterizations of stem cell differentiation into specific lineages, especially in non-destructive and non-invasive manner, are extremely important for generating patient-specific cells without mass loss of differentiated cells. Here, we report a new method capable of <I>in situ</I> label-free quantification of stem cell differentiation into multiple lineages, even at a single cell level. The human adipose-derived mesenchymal stem cells (hADMSCs) were first differentiated into two different types of cells (osteoblasts and adipocytes) and these differentiated cells were then intensively analyzed by micro-Raman spectroscopy. Interestingly, the Raman peaks assigned to lipid droplets and hydroxyapatite were found to be highly specific to the adipocyte (fat cell) and osteoblast (bone cell) and were thus found to be useful for generating label-free single cell Raman images in combination with CH<SUB>3</SUB> (2935 cm<SUP>−1</SUP>) peaks for visualizing cell shape. Remarkably, based on these Raman images, we found that the osteogenesis of hADMSCs could be determined and quantified after 9 days of differentiation, which is a week earlier than with the typical alizarin red staining method. In the case of adipogenesis, the increase of lipid droplets in the cytoplasm at the single cell level could be clearly visualized and detected during the entire period of adipogenesis, which is impossible using any other currently available methods such as Oil Red O and immunostaining. Hence, the new method reported in this study is highly promising as an analytical tool for precise <I>in-situ</I> monitoring of stem cell differentiation, and could facilitate the use of stem cell-based materials for the regenerative therapies.</P>
Lee, Ilbok,Kim, Jaekwang,Kim, Daeun,Kim, Hyosung,Hwang, Kee Bum,Son, Hyungbin,Yoon, Songhun Pergamon Press 2017 Electrochimica Acta Vol. No.
<P><B>Abstract</B></P> <P>The concentration of sulfate ions was continuously monitored by Raman spectroscopy during the preparation of cathode material precursors. The obtained spectra were used for the quantitative analysis of sulfate ions by comparison with a reference solution, and a gradual increase of sulfate ion concentration was detected. Using a mathematical approach, a time-dependent equation describing sulfate ion concentration was theoretically derived, and the calculated concentrations were compared with the measured ones, showing good agreement between these values. Due to the increased sulfate ion concentration, the metal hydroxide cathode precursor became more contaminated with elemental sulfur. Two as-obtained hydroxide powders with different sulfur impurity contents were calcined with a lithium source, producing cathode materials. Electrochemical analysis of the prepared cathode materials showed that morphological aspects (such as particle size) more highly affected the cathode performance more than the sulfur impurity content.</P>
Kang, Ee-Seul,Kim, Da-Seul,Han, Yoojoong,Son, Hyungbin,Chung, Yong-Ho,Min, Junhong,Kim, Tae-Hyung MDPI 2018 INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Vol.19 No.3
<P>Graphene derivatives have immense potential in stem cell research. Here, we report a three-dimensional graphene/arginine-glycine-aspartic acid (RGD) peptide nanoisland composite effective in guiding the osteogenesis of human adipose-derived mesenchymal stem cells (ADSCs). Amine-modified silica nanoparticles (SiNPs) were uniformly coated onto an indium tin oxide electrode (ITO), followed by graphene oxide (GO) encapsulation and electrochemical deposition of gold nanoparticles. A RGD–MAP–C peptide, with a triple-branched repeating RGD sequence and a terminal cysteine, was self-assembled onto the gold nanoparticles, generating the final three-dimensional graphene–RGD peptide nanoisland composite. We generated substrates with various gold nanoparticle–RGD peptide cluster densities, and found that the platform with the maximal number of clusters was most suitable for ADSC adhesion and spreading. Remarkably, the same platform was also highly efficient at guiding ADSC osteogenesis compared with other substrates, based on gene expression (alkaline phosphatase (ALP), runt-related transcription factor 2), enzyme activity (ALP), and calcium deposition. ADSCs induced to differentiate into osteoblasts showed higher calcium accumulations after 14–21 days than when grown on typical GO-SiNP complexes, suggesting that the platform can accelerate ADSC osteoblastic differentiation. The results demonstrate that a three-dimensional graphene–RGD peptide nanoisland composite can efficiently derive osteoblasts from mesenchymal stem cells.</P>
Effects of two-dimensional materials on human mesenchymal stem cell behaviors
Suhito, Intan Rosalina,Han, Yoojoong,Kim, Da-Seul,Son, Hyungbin,Kim, Tae-Hyung Academic Press 2017 Biochemical and biophysical research communication Vol. No.
<P><B>Abstract</B></P> <P>Graphene, a typical two-dimensional (2D) material, is known to affect a variety of stem cell behaviors including adhesion, spreading, growth, and differentiation. Here, we report for the first time the effects of four different emerging 2D materials on human adipose-derived mesenchymal stem cells (hADMSCs). Graphene oxide (GO), molybdenum sulfide (MoS<SUB>2</SUB>), tungsten sulfide (WS<SUB>2</SUB>), and boron nitride (BN) were selected as model two-dimensional materials and were coated on cell-culture substrates by a drop-casting method. Acute toxicity was not observed with any of the four different 2D materials at a low concentration range (<5 μg/ml). Interestingly, the 2D material-modified substrates exhibited a higher cell adhesion, spreading, and proliferation when compared with a non-treated (NT) substrate. Remarkably, in the case of differentiation, the MoS<SUB>2</SUB>-, WS<SUB>2</SUB>-, and BN-modified substrates exhibited a better performance in terms of guiding the adipogenesis of hADMSCs when compared with both NT and GO-modified substrates, based on the mRNA expression level (qPCR) and amount of lipid droplets (ORO staining). In contrast, the osteogenesis was found to be most efficiently induced by the GO-coated substrate (50 μg/mL) among all 2D-material coated substrates. In summary, 2D materials could act as favorable sources for controlling the stem cell growth and differentiation, which might be highly advantageous in both biomedical research and therapy.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The toxicity of four different two-dimensional materials on hADMSCs was studied. </LI> <LI> All four different 2D materials enhanced the cell adhesion, spreading and proliferation. </LI> <LI> WS<SUB>2</SUB>-, MoS<SUB>2</SUB>-, and BN-coated substrates enhanced the adipogenesis of hADMSCs. </LI> <LI> GO showed the best performance for guiding the osteogenesis of hADMSCs. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>