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- 저자 : Hyeon Muk Lim (검색결과 20 건)
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Lim, Jung Yeon,Park, Sang In,Oh, Ji Hyeon,Kim, Seong Muk,Jeong, Chang Hyun,Jun, Jin Ae,Lee, Kwan-Sung,Oh, Wonil,Lee, Jae-Kwon,Jeun, Sin-Soo Wiley Subscription Services, Inc., A Wiley Company 2008 Journal of neuroscience research Vol.86 No.10
<P>Brain-derived neurotrophic factor (BDNF) plays an important role in the differentiation, development, and survival of neural stem cells. In this study, we analyzed its effects on the stimulation of human umbilical cord blood-derived mesenchymal stem cells in terms of their potential to differentiate into neuron-like cells, their survival characteristics, and the molecular mechanisms involved. The treatment of cells with neural induction medium (NIM) and BDNF generated more cells that were neuron-like and produced stronger expression of neural-lineage markers than cells treated with NIM and without BDNF. Raf-1 and ERK phosphorylation and p35 expression levels increased significantly in cells treated with both NIM and BDNF. This treatment also effectively blocked cell death following neural induction and increased Akt phosphorylation and Bcl2 expression compared with cells treated with NIM without BDNF. Inhibition of ERKs inhibited the BDNF-stimulated up-regulation of p35 and Bcl2. In addition, the inhibition of PI3K abrogated Akt phosphorylation and Bcl2 expression, but not p35 expression. Thus, MAPK/ERK-dependent p35 up-regulation and MAPK/ERK-dependent and PI3K/Akt-dependent Bcl2 up-regulation contribute to BDNF-stimulated neural differentiation and to the survival of differentiated cells. © 2008 Wiley-Liss, Inc.</P>
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Lim, Jun-Muk,Won, Ji-Hye,Lee, Hyeon-Ji,Hong, Young Taik,Lee, Moo-Seok,Ko, Chang Hyun,Lee, Sang-Young The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.35
<P>We demonstrate polyimide (PI) nonwoven fabric-reinforced, flexible proton-conductive phosphosilicate glass composite membranes for potential application in high-temperature/low-humidity proton exchange membrane fuel cells (PEMFCs). The new reinforced composite membrane is fabricated <I>via</I> the impregnation of a 3-glycidyloxypropyl trimethoxysilane (GPTMS)/orthophosphoric acid (H<SUB>3</SUB>PO<SUB>4</SUB>) mixture into a PI nonwoven substrate followed by <I>in situ</I> sol–gel synthesis and hydrothermal treatment. This unique structural integrity enables the reinforced composite membrane to provide unprecedented improvement in the mechanical properties (notably flexibility and thickness) over typical bulk phosphosilicate glasses that are highly fragile and thick. Meanwhile, the highly porous structure of the PI reinforcing framework allows for the facile formation of a three-dimensionally interconnected phosphosilicate glass matrix in the reinforced composite membrane, which in turn offers favorable pathways for proton transport. Another advantageous feature of the reinforced composite membrane is higher proton conductivity under dehumidified conditions, as compared to a hydration-dependent polymer electrolyte membrane such as sulfonated poly(arylene ether sulfone) (SPAES). This superior proton conductivity of the reinforced composite membrane is further discussed with in-depth consideration of its architectural novelty and proton transport phenomena governed by the Grotthuss mechanism.</P> <P>Graphic Abstract</P><P>A PI nonwoven fabric-reinforced, flexible protonconductive phosphosilicate glass composite membrane is fabricated for high-temperature/low humidity PEMFCs. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2jm33406b'> </P>
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Lim, Jung Yeon,Park, Sang In,Kim, Seong Muk,Jun, Jin Ae,Oh, Ji Hyeon,Ryu, Chung Hun,Jeong, Chang Hyun,Park, Sun Hwa,Park, Soon A,Oh, Wonil,Chang, Jong Wook,Jeun, Sin-Soo Pergamon Press ; Elsevier Science Ltd ; Elsevier S 2011 CELL TRANSPLANTATION Vol.20 No.11
<P>The ability of mesenchymal stem cells (MSCs) to differentiate into neural cells makes them potential replacement therapeutic candidates in neurological diseases. Presently, overexpression of brain-derived neurotrophic factor (BDNF), which is crucial in the regulation of neural progenitor cell differentiation and maturation during development, was sufficient to convert the mesodermal cell fate of human umbilical cord blood-derived MSCs (hUCB-MSCs) into a neuronal fate in culture, in the absence of specialized induction chemicals. BDNF overexpressing hUCB-MSCs (MSCs-BDNF) yielded an increased number of neuron-like cells and, surprisingly, increased the expression of neuronal phenotype markers in a time-dependent manner compared with control hUCB-MSCs. In addition, MSCs-BDNF exhibited a decreased labeling for MSCs-related antigens such as CD44, CD73, and CD90, and decreased potential to differentiate into mesodermal lineages. Phosphorylation of the receptor tyrosine kinase B (TrkB), which is a receptor of BDNF, was increased significantly in MSC-BDNF. BDNF overexpression also increased the phosphorylation of β-catenin and extracellular signal-regulated kinases (ERKs). Inhibition of TrkB availability by treatment with the TrkB-specific inhibitor K252a blocked the BDNF-stimulated phosphorylation of β-catenin and ERKs, indicating the involvement of both the β-catenin and ERKs signals in the BDNF-stimulated and TrkB-mediated neural differentiation of hUCB-MSCs. Reduction of β-catenin availability using small interfering RNA-mediated gene silencing inhibited ERKs phosphorylation. However, β-catenin activation was maintained. In addition, inhibition of β-catenin and ERKs expression levels abrogated the BDNF-stimulated upregulation of neuronal phenotype markers. Furthermore, MSC-BDNF survived and migrated more extensively when grafted into the lateral ventricles of neonatal mouse brain, and differentiated significantly into neurons in the olfactory bulb and periventricular astrocytes. These results indicate that BDNF induces the neural differentiation of hUCB-MSCs in culture via the TrkB-mediated phosphorylation of ERKs and β-catenin and following transplantation into the developing brain.</P>
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Lee, Hyeon-Ji,Lim, Jun-Muk,Kim, Hyun-Woo,Jeong, Sang-Hwan,Eom, Seung-Wook,Hong, Young Taik,Lee, Sang-Young Elsevier 2016 Journal of membrane science Vol.499 No.-
<P><B>Abstract</B></P> <P>Despite the commercial success of primary Zinc (Zn)–air batteries, rechargeable Zn–air batteries are still far behind meaningful performance levels. Among numerous challenges facing rechargeable Zn–air batteries, from the material point of view, separator membranes should not be underestimated, along with other battery components such as anodes, cathodes and electrolytes. More particularly, crossover of soluble zincate Zn OH 4 2 - ions through separator membranes from Zn anode to air cathode, which significantly affects electrochemical performance of Zn–air cells, has hardly been addressed. Here, as a facile and scalable strategy to resolve the separator membrane-related issues, we demonstrate a new class of electrospun nanofiber mat-reinforced permselective composite membranes (referred to as ERC membranes) and explore their potential contribution to development of rechargeable Zn–air cells in terms of transport phenomena of hydroxyl (OH<SUP>−</SUP>) and Zn OH 4 2 - ions. The ERC membrane is fabricated by impregnating polyvinyl alcohol (PVA) into electrospun polyetherimide (PEI) nanofiber mat. The PEI nanofiber mat acts as a compliant framework to endow dimensional stability and mechanical strength. The PVA matrix, after being swelled with electrolyte solution, provides ion size (OH<SUP>−</SUP> vs. Zn OH 4 2 - )-dependent conductive pathways. This architecture/material uniqueness of the ERC membrane effectively suppresses permeation of bulky Zn OH 4 2 - ions without impairing OH<SUP>−</SUP> conduction, thereupon achieving exceptional cycle capacity retention of Zn–air cells far beyond those accessible with conventional microporus polyolefin separators. The ERC membrane featuring the ion size exclusion-based permselectivity opens a new membrane-driven opportunity that leads us closer toward rechargeable Zn–air batteries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Membrane-driven opportunity to facilitate progress of rechargeable Zn-air cells. </LI> <LI> Electrospun PEI nanofiber mat-reinforced permselective PVA separator membrane. </LI> <LI> The new separator shows superior permselective transport of OH<SUP>−</SUP> and Zn OH 4 2 - ions. </LI> <LI> The exceptional permselectivity improves cycle capacity retention of Zn–air cells. </LI> <LI> Structural analysis of cathode surface after cycling verifies separator contribution. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Lee, Hyeon-Ji,Kim, Jung-Hwan,Won, Ji-Hye,Lim, Jun-Muk,Hong, Young Taik,Lee, Sang-Young American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.11
<P>We demonstrate highly flexible, proton-conductive silicate glass electrolytes integrated with polyimide (PI) nonwoven fabrics (referred to as “b-SS glass electrolytes”) for potential use in medium-temperature/low-humidity proton exchange membrane fuel cells (PEMFCs). The b-SS glass electrolytes are fabricated via in situ sol–gel synthesis of 3-trihydroxysilyl-1-propanesulfonic acid (THPSA)/3-glycidyloxypropyl trimethoxysilane (GPTMS) mixtures inside PI nonwoven substrates that serve as a porous reinforcing framework. Owing to this structural uniqueness, the b-SS glass electrolytes provide noticeable improvements in mechanical bendability and membrane thickness, in comparison to typical bulk silicate glass electrolytes that are thick and easily fragile. Another salient feature of the b-SS glass electrolytes is the excellent proton conductivity at harsh measurement conditions of medium temperature/low humidity, which is highly important for PEMFC-powered electric vehicle applications. This beneficial performance is attributed to the presence of a highly interconnected, proton-conductive (THPSA/GPTMS-based) silicate glass matrix in the PI reinforcing framework. Notably, the b-SS glass electrolyte synthesized from THPSA/GPTMS = 9/1 (mol/mol) exhibits a higher proton conductivity than water-swollen sulfonated polymer electrolyte membranes (here, sulfonated poly(arylene ether sulfone) and Nafion are chosen as control samples). This intriguing behavior in the proton conductivity of the b-SS glass electrolytes is discussed in great detail by considering its structural novelty and Grotthuss mechanism-driven proton migration that is strongly affected by ion exchange capacity (IEC) values and also state of water.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-11/am400836h/production/images/medium/am-2013-00836h_0010.gif'></P>
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Jeong, Sang Hyeon,Park, Geun Chul,Choi, Jun Hyuk,Lee, Chang Min,Lee, Seung Muk,Seo, Tae Yang,Choi, Dae Hyuk,Jung, Seung Boo,Lim, Jun Hyung,Joo, Jinho American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.11
<P>Al-doped ZnO (AZO) nanorods (NRs) with different doping contents (actual content of 1.7%similar to 4.9%) were synthesized on p-type Si substrates using the hydrothermal method, and n-AZO NRs/p-Si heterojunction diodes were then fabricated using the NRs. The electrical property, chemical bonding states, and morphology of the AZO NRs were investigated through various analysis tools. The AZO NRs grew along the c-axis [001] direction with a hexagonal wurtzite structure, and the crystal structure and orientation of the NRs were not significantly influenced by the Al incorporation. On the other hand, while the average length and diameter of the AZO NRs decreased with increasing Al content, the density increased. From the XPS result, we found that the oxygen vacancy of the AZO increased as the Al content was increased due to the large surface to volume ratio. The current-voltage (I-V) curves revealed that electrical conductivity increased with increasing Al doping because of the increased number of charge carriers (electrons) provided by the Al3+ ions and oxygen vacancies.</P>
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Kim, Seong Muk,Oh, Ji Hyeon,Park, Soon A,Ryu, Chung Heon,Lim, Jung Yeon,Kim, Dal-Soo,Chang, Jong Wook,Oh, Wonil,Jeun, Sin-Soo Wiley (John WileySons) 2010 Stem Cells Vol.28 No.12
<P>Irradiation is a standard therapy for gliomas and many other cancers. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is one of the most promising candidates for cancer gene therapy. Here, we show that tumor irradiation enhances the tumor tropism of human umbilical cord blood-derived mesenchymal stem cells (UCB-MSCs) and the therapeutic effect of TRAIL delivered by UCB-MSCs. The sequential treatment with irradiation followed by TRAIL-secreting UCB-MSCs (MSC-TRAIL) synergistically enhanced apoptosis in either TRAIL-sensitive or TRAIL-resistant glioma cells by upregulating the death receptor 5 and by inducing caspase activation. Migration assays showed greater MSC migration toward irradiated glioma cells and the tumor site in glioma-bearing mice compared with unirradiated tumors. Irradiated glioma cells had increased expression of interleukin-8 (IL-8), which leads to the upregulation of the IL-8 receptor on MSCs. This upregulation, which is involved in the migratory capacity of UCB-MSCs, was confirmed by siRNA inhibition and an antibody-neutralizing assay. In vivo survival experiments in orthotopic xenografted mice showed that MSC-based TRAIL gene delivery to irradiated tumors had greater therapeutic efficacy than a single treatment. These results suggest that clinically relevant tumor irradiation increases the therapeutic efficacy of MSC-TRAIL by increasing tropism of MSCs and TRAIL-induced apoptosis, which may be a more useful strategy for cancer gene therapy.</P>
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Lee, Seung Muk,Seo, Tae Yang,Park, Geun Chul,Choi, Jun Hyuk,Jeong, Sang Hyeon,Jung, Seung-Boo,Choi, Dae Hyuk,Lim, Jun Hyung,Joo, Jinho American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.10
<P>Mesocrystal is a promising material for improving photocatalytic activity because of its large specific surface area and almost single crystalline structure. In this work, anatase TiO2 mesocrystals were synthesized via a simple hydrothermal process and the morphology and consequent photocatalytic property was controlled through hydrofluoride (HF) addition. The morphology of TiO2 was significantly varied with the amount of HF addition. The pure TiO2 was elliptical mesocrystal, having bipyramidal sub units with high portion of {101} facets, arraying in the [001] direction. Similar mesocrystal morphologies were obtained, but the sub unit size decreased as HF content increased to 0.01 wt%, and the shape of the sub unit then changed to nanosheet with the introduction of further HF (1-2 wt%). The 0.01 wt% sample exhibited superior photocatalytic activity over the pure sample, decomposing similar to 70% and similar to 80% methylene blue in 1 h for the pure sample and 0.01 wt% sample, respectively, resulting from enlarged specific surface area and fluorinated surface. The photocatalytic activity reduced to similar to 20% for the 1-2 wt% particles due to the decrease in surface area and formation of the TiOF2 phase. The present work suggests that the morphology and photocatalytic activity of TiO2 mesocrystal are facilely modified through HF introduction.</P>
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Kim, Hyun-Woo,Lim, Jun-Muk,Lee, Hyeon-Ji,Eom, Seung-Wook,Hong, Young Taik,Lee, Sang-Young The Royal Society of Chemistry 2016 Journal of materials chemistry. A, Materials for e Vol.4 No.10
<▼1><P>Artificially engineered, bicontinuous anion-conducting/-repelling polymeric phases were demonstrated as a selective ion transport channel to bring separator membrane-driven performance benefits for rechargeable Zn–air batteries.</P></▼1><▼2><P>Zinc (Zn)–air batteries have recently attracted a great deal of attention as a promising energy storage system to fulfill our ever-increasing demand for higher energy density power sources. Despite commercial success of primary Zn–air batteries, performances of rechargeable Zn–air batteries are still far below practically satisfactory levels. Among critical challenges facing the electrochemical rechargeability, the crossover of zincate (Zn(OH)4<SUP>2−</SUP>) ions from the Zn anode to the air cathode (<I>via</I> separator membranes) is a formidable bottleneck. Here, as a facile and scalable polymer architecture strategy to address this ion transport issue, we demonstrate a new class of polymer blend electrolyte membranes with artificially engineered, bicontinuous anion-conducting/-repelling phases (referred to as “PBE membranes”). As an anion-conducting continuous phase, an electrospun polyvinyl alcohol (PVA)/polyacrylic acid (PAA) nanofiber mat is fabricated. Into the PVA/PAA nanofiber mat, Nafion bearing pendant sulfonate groups is impregnated to form an anion-repelling continuous phase. Such bicontinuous phase-mediated structural uniqueness enables the PBE membrane to act as a selective ion transport channel, <I>i.e.</I>, effectively suppresses Zn(OH)4<SUP>2−</SUP> crossover (by a continuous Nafion phase offering the Donnan exclusion effect) with slightly impairing OH<SUP>−</SUP> conduction (predominantly through the PVA/PAA nanofiber mat), eventually improving the cycling stability (cycle time = over 2500 min for the PBE membrane <I>vs.</I> 900 min for a conventional polypropylene separator). The PBE membrane featuring the selective transport of OH<SUP>−</SUP> and Zn(OH)4<SUP>2−</SUP> ions is anticipated to pave a new route that leads us closer toward rechargeable Zn–air batteries.</P></▼2>
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