Inhibitory Effects of Triphlorethol-A on MMP-1 Induced by Oxidative Stress in Human Keratinocytes via ERK and AP-1 Inhibition

Kang, Kyoung Ah,Zhang, Rui,Piao, Mei Jing,Ko, Dong Ok,Wang, Zhi Hong,Lee, Kyung,Kim, Bum Joon,Shin, Taekyun,Park, Jae Woo,Lee, Nam Ho,Yoo, Byoung Sam,Hyun, Jin Won Taylor Francis 2008 Journal of toxicology and environmental health. Pa Vol.71 No.15

<P> Oxidative stress is known to generate reactive oxygen species (ROS) in cells, which subsequently induce the synthesis of matrix metalloproteinases (MMP) and an aging phenomenon. The protective effects of triphlorethol-A, derived from Ecklonia cava, were investigated against hydrogen peroxide (H2O2)-induced damage using human skin keratinocytes. Data showed that triphlorethol-A inhibited ROS formation, induced catalase expression, inhibited DNA damage, and increased cell viability in keratinocytes. Triphlorethol-A treatment significantly reduced MMP-1 expression and production, compared to H2O2-treated cells. In addition, triphlorethol-A abrogated the activation of extracellular signal regulated protein kinase (ERK), which originates upstream of MMP-1 expression, and was induced by H2O2 treatment. Moreover, triphlorethol-A inhibited DNA binding activity of activator protein-1 (AP-1), a downstream transcription factor of ERK. Data indicate that the antioxidative properties of triphlorethol-A involve the inhibition of MMP-1 via ERK and AP-1 inhibition.</P>

Thalamus surface shape deformity in obsessive-compulsive disorder and schizophrenia

Kang, Do-Hyung,Kim, Sun Hyung,Kim, Chi-Won,Choi, Jung-Seok,Jang, Joon Hwan,Jung, Myung Hun,Lee, Jong-Min,Kim, Sun I.,Kwon, Jun Soo Lippincott Williams Wilkins, Inc. 2008 NEUROREPORT - Vol.19 No.6

The authors performed a three-dimensional shape deformation analysis to clarify the various patterns of specific thalamic nuclei abnormality using three age-matched and sex-matched groups of 22 patients with obsessive-compulsive disorder (OCD), 22 patients with schizophrenia and 22 control participants. Compared with the healthy volunteers, the anterior, lateral outward surface deformities of the thalamus were significant in OCD patients, whereas the posterior, medial outward deformities of the thalamus were prominent in schizophrenia patients. In terms of thalamic asymmetry, both OCD and schizophrenia patients exhibited the loss of a leftward pattern of asymmetry on the posterior, medial surface of the thalamus. Different patterns of shape abnormality of specific thalamic nuclei may be related to the different phenomenology of OCD and schizophrenia.

Structural Health Monitoring Based on Electrical Impedance of a Carbon Nanotube Neuron

Kang, In Pil,Lee, Jong Won,Choi, Gyeong Rak,Jung, Joo Yung,Hwang, Sung Ho,Choi, Yeon Sun,Yoon, Kwang Joon,Schulz, Mark J. Trans Tech Publications, Ltd. 2006 Key Engineering Materials Vol.321 No.-

<P>This paper introduces a new sensor design based on a carbon nanotube structural neuron for structural health monitoring applications. The carbon nanotube neuron is a thin and narrow polymer film sensor that is bonded or deposited onto a structure. The electrochemical impedance (resistance and capacitance) of the neuron changes due to deterioration of the structure where the neuron is located. A network of the long carbon nanotube neurons can form a structural neural system to provide large area coverage and an assurance of the operational health of a structure without the need for actuators and complex wave propagation analyses that are used with other SHM methods. The neural system can also reduce the cost of health monitoring by using biomimetic signal processing to minimize the number of channels of data acquisition needed to detect damage. The carbon nanotube neuron is lightweight and easily applied to the structural surface, and there is no stress concentration, no piezoelectrics, no amplifier, and no storage of high frequency waveforms. The carbon nanotube neuron is expected to find applications in detecting damage and corrosion in large complex structures including composite and metallic aircraft and rotorcraft, bridges, and almost any type of structure with almost no penalty to the structure.</P>

Titanium dioxide nanoparticles trigger p53-mediated damage response in peripheral blood lymphocytes

Kang, Su Jin,Kim, Byeong Mo,Lee, Young Joon,Chung, Hai Won Wiley Subscription Services, Inc., A Wiley Company 2008 Environmental and molecular mutagenesis Vol.49 No.5

<P>Titanium dioxide nanoparticles (nano-TiO<SUB>2</SUB>) are widely used as a photocatalyst in air and water remediation. These nanoparticles are known to induce toxicity; however, their cytotoxic mechanism is not fully understood. In this study, we investigated the underlying mechanism of nano-TiO<SUB>2</SUB>-induced cytotoxicity in peripheral blood lymphocytes. We examined the genotoxic effects of nano-TiO<SUB>2</SUB> in lymphocytes using alkaline single-cell gel electrophoresis (Comet) and cytokinesis-block micronucleus (CBMN) assays. Lymphocytes treated with nano-TiO<SUB>2</SUB> showed significantly increased micronucleus formation and DNA breakage. Western-blot analysis to identify proteins involved in the p53-mediated response to DNA damage revealed the accumulation of p53 and activation of DNA damage checkpoint kinases in nano-TiO<SUB>2</SUB>-treated lymphocytes. However, p21 and bax, downstream targets of p53, were not affected, indicating that nano-TiO<SUB>2</SUB> does not stimulate transactivational activity of p53. The generation of reactive oxygen species (ROS) in nano-TiO<SUB>2</SUB>-treated cells was also observed, andN-acetylcysteine (NAC) supplementation inhibited the level of nano-TiO<SUB>2</SUB>-induced DNA damage. Given that ROS-induced DNA damage leads to p53 activation in the DNA damage response, our results suggest that nano-TiO<SUB>2</SUB> induces ROS generation in lymphocytes, thereby activating p53-mediated DNA damage checkpoint signals. Environ. Mol. Mutagen., 2008. © 2008 Wiley-Liss, Inc.</P>

The Effects of Whitening Components on Human Melanocytes on vitro

( Joon-hwan Cho ),( Ki-moo Lee ),( Nam-soo Kim ),( Won-hyoung Kang ) 대한화장품학회 1997 대한화장품학회지 Vol.23 No.3

To identify inhibitors of melanogenesis, we compared the effects of 5 compounds on mushroom tyrosinase, human melanocytic tyrosinase activity and melanin content. The cytotoxicyty of the components were also tested on cultured human melanoctes. Kojic acid showed marked inhibitory effect both on mushroom and human tyrosinase activity. This action of kijic acid is stronger than that of ascorbic acid. Arbutin inhibited human tyrosinase activity of cultured melanocytes although it had slightly inhibitory effect on mushroom tyrosinase activity. Azelaic acid had no effect on human tyrosinase activity. Melanin production was inhibited significantly by kojic acid and tranexamic acid. MTT assay showed that all of the compounds were non-cytotoxic to melanocytes at the concentrations tested. These results suggest that the effect of kojic acid on cultured meanocytes involve inhibition of tyrosinase activity and melanogenesis without affection the cell number.

Inhibitory effects of glycitein on hydrogen peroxide induced cell damage by scavenging reactive oxygen species and inhibiting c-Jun N-terminal kinase

Kang, Kyoung Ah,Zhang, Rui,Piao, Mei Jing,Lee, Kyoung Hwa,Kim, Bum Joon,Kim, So Young,Kim, Hee Sun,Kim, Dong Hyun,You, Ho Jin,Hyun, Jin Won Informa Healthcare 2007 Free radical research Vol.41 No.6

<P> The present study investigated the cytoprotective properties of glycitein, a metabolite formed by the transformation of glycitin by intestinal microflora, against oxidative stress. Glycitein was found to scavenge intracellular reactive oxygen species (ROS), and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, and thereby preventing lipid peroxidation and DNA damage. Glycitein inhibited apoptosis of Chinese hamster lung fibroblast (V79-4) cells exposed to hydrogen peroxide (H2O2) via radical scavenging activity. Glycitein abrogated the activation of c-Jun N-terminal kinase (JNK) induced by H2O2 treatment and inhibited DNA binding activity of activator protein-1 (AP-1), a downstream transcription factor of JNK. Taken together, these findings suggest that glycitein protected H2O2 induced cell death in V79-4 cells by inhibiting ROS generation and JNK activation.</P>

Development of a piezoelectric unimorph using a mechanically pre-stressed substrate

Kang, Lae-Hyong,Lee, Jong-Won,Han, Jae-Hung,Chung, Sang-Joon,Ko, Han-Young Institute of Physics Publishing 2009 Smart materials & structures Vol.18 No.10

<P>This paper proposes a novel curved shape piezoelectric unimorph called PUMPS (piezoelectric unimorph with mechanically pre-stressed substrate) that uses a new and simple fabrication method. Generally, conventional pre-stressed curved shape unimorphs are made by using high-temperature adhesion processes and the thermal expansion coefficient mismatch of their constituent layers. In the conventional methods, therefore, it is necessary to use materials with different thermal expansion coefficients, high-temperature ovens or autoclaves, and special adhesives. In addition, the conventional methods generally require the re-poling of the piezoceramic actuator layer due to high-temperature adhesion near or above the Curie temperature of the piezoceramic. The present fabrication method uses mechanically pre-stressed substrates and a room temperature adhesion process instead of relying on a thermal coefficient mismatch. First, a substrate material is strained in the longitudinal direction and then a piezoelectric material is attached to the substrate. A difference of mechanical strains between the substrate and the piezoelectric layer causes the final manufactured actuator to curve. In this way, a new type of curved shape pre-stressed piezoelectric unimorph, PUMPS, can be easily fabricated at room temperature and can be used as a sensor, an actuator and an energy-harvesting element without the necessity of a re-poling process. A series of performance tests on the proposed PUMPS actuators was accomplished and the test results show that the actuation capability of PUMPS is comparable to that of conventional curved shape actuators, in spite of the much simpler manufacturing process. </P>

Extended Kalman Filter Approach to Dynamic Electrical Impedance Tomography with Internal Electrodes

Kang, Suk-In,Kim, Kyung-Youn,Kim, Ho-Chan,Cho, Won-Churl,KIm, Min-Chan,Kim, Sin,Lee, Heon-Ju,Lee, Yoon-Joon 제주대학교 공과대학 첨단기술연구소 2001 尖端技術硏究所論文集 Vol.12 No.2

Electrical impedance tomography (EIT) is a relatively new imaging modality in which the internal impedivity distribution is reconstructed based on the known sets of injected currents through the electrodes and induced voltages on the surface of the object. We describe a dynamic EIT imaging technique for the case where the resistivity distribution inside the object changes rapidly within the time taken to acquire a full set of independent measurement data. In doing so, the inverse problem is treated as the nonlinear state estimation problem and the unknown state(resistivity) is estimated with the aid of extended Kalman filter in a minimum mean square error sense. In particular, additional electrodes are attached to the known internal structure of the object to enhance the reconstruction performance and generalized Tikhonov regularization technique is employed to mitigate the ill-posedness of the inverse problem. Computer simulations are provided to illustrate the reconstruction performance of the proposed algorithm.

Self-assembled, highly crystalline porous ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) interlayer for Si/organic hybrid solar cells

Kang, Sung Bum,Jeong, Myeong Hoon,Choi, In Young,Sohn, So-Dam,Kim, Su Han,Shin, Hyung-Joon,Park, Won Il,Shin, Jae Cheol,Song, Myoung Hoon,Choi, Kyoung Jin Elsevier 2017 Nano energy Vol.41 No.-

<P><B>Abstract</B></P> <P>Ferroelectric polymers can effectively improve the photovoltaic performance of solar cells, inducing an electric field to promote the dissociation of electron-hole pairs, with the thus generated charges collected from open pores. Since such performance enhancement requires materials with a unique porous crystalline structure, we herein present a novel route to highly crystalline and porous poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) thin films utilizing a <I>modified</I> breath figure method based on spin coating. The key feature of the above method is the addition of small amounts of water to the acetone/P(VDF-TrFE) solution to produce porous ferroelectric thin films which have significantly higher crystallinity values than nanostructures or films prepared by other methods. Furthermore, <I>n</I>-Si / poly(3,4-ethylene dioxy thiophene):poly(styrene sulfonate) hybrid solar cells with porous P(VDF-TrFE) interlayers are demonstrated to exhibit spontaneous polarization sufficient for increasing their open circuit voltages and fill factors. Finite-difference time-domain simulation reveals that the electric field due to the above spontaneous polarization increases the built-in electric field of the Schottky junction between <I>n</I>-Si and poly(3,4-ethylene dioxy thiophene):poly(styrenesulfonate) and reduces the reverse leakage current of the Schottky diode. Thus, the organic ferroelectric thin films with controlled porosity proposed in this study are well suited for a broad range of optoelectronic applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> High crystalline and self-assembled porous thin films are fabricated by simple and facile method. </LI> <LI> The addition of small amounts of water to the acetone/P(VDF-TrFE) solution to produce porous ferroelectric thin films. </LI> <LI> Photovoltaic parameters are enhanced due to spontaneous polarization of the P(VDF-TrFE) interlayer. </LI> <LI> FDTD simulation reveals that the spontaneous polarization increases the built-in electric field of solar cells. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Self-assembled porous ferroelectric Poly(Vinylidene fluoride-co-trifluoroethylene) thin films are fabricated using a simple spin coating method. The prepared ferroelectric porous thin films enable the application in poly(3,4- ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) / n-Si hybrid solar cells. The power conversion efficiency of optimized device is 10% higher than the device without the ferroelectric layer. The mechanism responsible for the enhanced performance of PEDOT:PSS / P(VDF-TrFE) / n-Si hybrid solar cells is clarified based on finite-difference time-domain simulations.</P> <P>[DISPLAY OMISSION]</P>

Direct growth of doping controlled monolayer WSe₂ by selenium-phosphorus substitution

Kang, Won Tae,Lee, Il Min,Yun, Seok Joon,Song, Young Il,Kim, Kunnyun,Kim, Do-Hwan,Shin, Yong Seon,Lee, Kiyoung,Heo, Jinseong,Kim, Young-Min,Lee, Young Hee,Yu, Woo Jong The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.24

<P>Although many studies have been carried out on the doping of transition metal dichalcogenides (TMDCs), introducing controllable amounts of dopants into a TMD lattice is still insufficient. Here we demonstrate doping controlled TMDC growth by the replacement of selenium with phosphorus during the synthesis of the monolayer WSe2. The phosphorus doping density was precisely controlled by fine adjustment of the amount of P2O5 dopant powder along the pre-annealing time. Raman spectroscopy, photoluminescence (PL), X-ray photoelectron spectroscopy (XPS), and high-angle annular bright field scanning tunneling electron microscopy (HAADF STEM) provide evidence that P doping occurs within the WSe2 crystal with P occupying the substitutional Se sites. With regard to its electrical characteristics, the hole majority current of P-doped WSe2 is 100-times higher than that of the intrinsic WSe2. The measured doping concentration ranged from ∼8.16 × 10<SUP>10</SUP> to ∼1.20 × 10<SUP>12</SUP> depending on the amount of P2O5 dopant powder by pre-annealing.</P>