143 results on '"Wan-Joong Kim"'
Search Results
2. Cubic Nonlinearity of Graphene-Oxide Monolayer
- Author
-
Tikaram Neupane, Uma Poudyal, Bagher Tabibi, Wan-Joong Kim, and Felix Jaetae Seo
- Subjects
one-photon transition ,two-photon transition ,2D materials ,nonlinear absorption ,nonlinear refraction ,Technology ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Microscopy ,QH201-278.5 ,Descriptive and experimental mechanics ,QC120-168.85 - Abstract
The cubic nonlinearity of a graphene-oxide monolayer was characterized through open and closed z−scan experiments, using a nano-second laser operating at a 10 Hz repetition rate and featuring a Gaussian spatial beam profile. The open z−scan revealed a reverse saturable absorption, indicating a positive nonlinear absorption coefficient, while the closed z−scan displayed valley-peak traces, indicative of positive nonlinear refraction. This observation suggests that, under the given excitation wavelength, a two-photon or two-step excitation process occurs due to the increased absorption in both the lower visible and upper UV wavelength regions. This finding implies that graphene oxide exhibits a higher excited-state absorption cross-section compared to its ground state. The resulting nonlinear absorption and nonlinear refraction coefficients were estimated to be approximately ~2.62 × 10−8 m/W and 3.9 × 10−15 m2/W, respectively. Additionally, this study sheds light on the interplay between nonlinear absorption and nonlinear refraction traces, providing valuable insights into the material’s optical properties.
- Published
- 2023
- Full Text
- View/download PDF
3. Spatial Self-Phase Modulation in Graphene-Oxide Monolayer
- Author
-
Tikaram Neupane, Bagher Tabibi, Wan-Joong Kim, and Felix Jaetae Seo
- Subjects
spatial self-phase modulation ,graphene-oxide atomic layer ,nonlinear refraction ,Crystallography ,QD901-999 - Abstract
The spatial self-phase modulation (SSPM) of the optical field revealed the magnitude and polarity of nonlinear refraction coefficients of the graphene-oxide (GO) atomic layers in an aqueous base solution with a resonant excitation using a chopped quasi-static laser at 532 nm. The SSPM of the optical field as a result of the intrinsic nonlinear refraction coefficient of GO atomic layers and the spatial distribution of intensity displayed the concentric diffraction rings at the far field due to the coherent superposition of transverse wave vectors. The number of concentric rings as a function of the applied intensity revealed the nonlinear refraction coefficient of GO which was estimated to be ~–6.65 × 10−12 m2/W for the laser-excitation duration of ~0.32 s, where the negative polarity of nonlinear refraction coefficient was confirmed with the interference image profile of SSPM. The upper and vertical distortion of concentric rings at the far field at the longer laser-excitation duration of ~0.8 s indicates the distortion of the coherent superposition of transverse wave vectors due to the localized thermal vortex of GO in the aqueous solution that offers novel platforms of thermal metrology based on localized optical nonlinearity and temperature-sensitive all-optical switching.
- Published
- 2023
- Full Text
- View/download PDF
4. Linoleic Acid Attenuates Denervation-Induced Skeletal Muscle Atrophy in Mice through Regulation of Reactive Oxygen Species-Dependent Signaling
- Author
-
Myung-Hun Lee, Jin-Ho Lee, Wan-Joong Kim, Seo Ho Kim, Sun-Young Kim, Han Sung Kim, and Tack-Joong Kim
- Subjects
antioxidant ,linoleic acid ,muscle atrophy ,oxidative stress ,sciatic denervation ,Biology (General) ,QH301-705.5 ,Chemistry ,QD1-999 - Abstract
Muscle atrophy is a major muscle disease, the symptoms of which include decreased muscle volume leading to insufficient muscular support during exercise. One cause of muscle atrophy is the induction of oxidative stress by reactive oxygen species (ROS). This study aimed to identify the antioxidant mechanism of linoleic acid (LA) in muscle atrophy caused by oxidative stress. H2O2 has been used to induce oxidative stress in myoblasts in vitro. C2C12 myoblasts treated with H2O2 exhibited decreased viability and increased ROS synthesis. However, with LA treatment, the cells tended to recover from oxidative effects similar to those of the control groups. At the molecular level, the expression of superoxide dismutase 1 (SOD1), Bax, heat shock protein 70 (HSP70), and phosphorylated forkhead box protein O1 was increased by oxidative stress, causing apoptosis. LA treatment suppressed these changes. In addition, the expression of MuRF1 and Atrogin-1/MAFbx mRNA increased under oxidative stress but not in the LA-treated group. Sciatic denervation of C57BL/6 mice manifested as atrophy of the skeletal muscle in micro-computed tomography (micro-CT). The protein expression levels of SOD1, HSP70, and MuRF1 did not differ between the atrophied muscle tissues and C2C12 myoblasts under oxidative stress. With LA treatment, muscle atrophy recovered and protein expression was restored to levels similar to those in the control. Therefore, this study suggests that LA may be a candidate substance for preventing muscle atrophy.
- Published
- 2022
- Full Text
- View/download PDF
5. Synergistic Use of Gold Nanoparticles (AuNPs) and 'Capillary Enzyme-Linked Immunosorbent Assay (ELISA)' for High Sensitivity and Fast Assays.
- Author
-
Wan-Joong Kim, Hyo Young Cho, Bongjin Jeong, Sangwon Byun, JaeDoo Huh, and Young Jun Kim
- Published
- 2018
- Full Text
- View/download PDF
6. Synergistic Use of Gold Nanoparticles (AuNPs) and 'Capillary Enzyme-Linked Immunosorbent Assay (ELISA)' for High Sensitivity and Fast Assays
- Author
-
Wan-Joong Kim, Hyo Young Cho, Bongjin Jeong, Sangwon Byun, JaeDoo Huh, and Young Jun Kim
- Subjects
capillary ELISA ,ImmunoGold conjugate ,C-reactive protein (CRP) ,point-of-care (POC) ,Chemical technology ,TP1-1185 - Abstract
Using gold nanoparticles (AuNPs) on “capillary enzyme-linked immunosorbent assay (ELISA)”, we produced highly sensitive and rapid assays, which are the major attributes for point-of-care applications. First, in order to understand the size effect of AuNPs, AuNPs of varying diameters (5 nm, 10 nm, 15 nm, 20 nm, 30 nm, and 50 nm) conjugated with Horseradish Peroxidase (HRP)-labeled anti-C reactive protein (antiCRP) (AuNP•antiCRP-HRP) were used for well-plate ELISA. AuNP of 10 nm produced the largest optical density, enabling detection of 0.1 ng/mL of CRP with only 30 s of incubation, in contrast to 10 ng/mL for the ELISA run in the absence of AuNP. Then, AuNP of 10 nm conjugated with antiCRP-HRP (AuNP•antiCRP-HRP) was used for “capillary ELISA” to detect as low as 0.1 ng/mL of CRP. Also, kinetic study on both 96-well plates and in a capillary tube using antiCRP-HRP or AuNP•antiCRP-HRP showed a synergistic effect between AuNP and the capillary system, in which the fastest assay was observed from the “AuNP capillary ELISA”, with its maximum absorbance reaching 2.5 min, while the slowest was the typical well-plate ELISA with its maximum absorbance reaching in 13.5 min.
- Published
- 2017
- Full Text
- View/download PDF
7. The Effect of Financial Activities on Determinants of Corporate Cash Holdings
- Author
-
Wan-Joong Kim
- Subjects
Finance ,business.industry ,Corporate group ,Cash holdings ,Agency cost ,Business - Published
- 2018
8. Highly flexible, mechanically stable, and sensitive NO2 gas sensors based on reduced graphene oxide nanofibrous mesh fabric for flexible electronics
- Author
-
Dae-Sik Lee, Yongseok Jun, Yong Ju Yun, Jong Ho Shin, Wan Joong Kim, Hyung Ju Park, and Hyung-Kun Lee
- Subjects
Materials science ,Bend radius ,Oxide ,Nanotechnology ,02 engineering and technology ,Bending ,010402 general chemistry ,01 natural sciences ,law.invention ,chemistry.chemical_compound ,law ,Materials Chemistry ,Electrical and Electronic Engineering ,Instrumentation ,Graphene oxide paper ,Graphene ,Metals and Alloys ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Flexible electronics ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry ,Nanofiber ,Deformation (engineering) ,0210 nano-technology - Abstract
Flexible gas sensors with high-sensitivity and good stability are essential components of wearable electronic devices. In this paper, we present a novel graphene fabric gas sensor composed of reduced graphene oxide (RGO) nanosheets and electrospun nylon-6 nanofibers. By combination the RGO with nanofiber, the graphene electronic fabrics show sensitive response to NO 2 (13.6%@1 ppm) at room temperature, and excellent mechanical reliability against repeated deformation during 5000 bending cycles with an extreme bending radius of 1.0 mm.
- Published
- 2018
9. Analysis of KTB Market Liquidity Premium
- Author
-
Wan-Joong Kim
- Subjects
Bid–ask spread ,Monetary economics ,Business ,Market liquidity - Published
- 2018
10. Label-Free and Recalibrated Multilayer MoS2 Biosensor for Point-of-Care Diagnostics
- Author
-
Heekyeong Park, Sunkook Kim, Geonwook Yoo, Joonhyung Lee, Hyungbeen Lee, AbdulAziz AlMutairi, Young Jun Kim, Wan-Joong Kim, Seok Hwan Jeong, Muhammad Naqi, Gyuchull Han, Youngki Yoon, and Sang Woo Lee
- Subjects
chemistry.chemical_classification ,Materials science ,Biomolecule ,Point-of-care testing ,Transistor ,technology, industry, and agriculture ,Molecular binding ,Nanotechnology ,macromolecular substances ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,law.invention ,chemistry ,law ,General Materials Science ,Field-effect transistor ,Sensitivity (control systems) ,0210 nano-technology ,Biosensor ,Label free - Abstract
Molybdenum disulfide (MoS2) field-effect transistor (FET)-based biosensors have attracted significant attention as promising candidates for highly sensitive, label-free biomolecule detection devices. In this paper, toward practical applications of biosensors, we demonstrate reliable and quantitative detection of a prostate cancer biomarker using the MoS2 FET biosensor in a nonaqueous environment by reducing nonspecific molecular binding events and realizing uniform chemisorption of anti-PSA onto the MoS2 surface. A systematic and statistical study on the capability of the proposed device is presented, and the biological binding events are directly confirmed and characterized through intensive structural and electrical analysis. Our proposed biosensor can reliably detect various PSA concentrations with a limit of 100 fg/mL. Moreover, rigorous theoretical simulations provide a comprehensive understanding of the operating mechanism of the MoS2 FET biosensors, and further suggests the enhancement of the sensitivity through engineering device design parameters.
- Published
- 2017
11. Preparation and characterization of PET blended with silica–polystyrene hybrid nanocomposites
- Author
-
Wan-Joong Kim, Chul Am Kim, and Sanghee Kim
- Subjects
Nanocomposite ,Materials science ,Polymers and Plastics ,Scanning electron microscope ,Emulsion polymerization ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,X-ray photoelectron spectroscopy ,chemistry ,Materials Chemistry ,Polyethylene terephthalate ,Crystallite ,Polystyrene ,Fourier transform infrared spectroscopy ,Composite material ,0210 nano-technology - Abstract
Silica–polystyrene (Si–PS) nanocomposite latex particles were prepared by emulsion polymerization using Hwangtoh clay as the silica source and blending with polyethylene terephthalate (PET) by melt extrusion. The Hwangtoh clay was mechanically grounded as nanoscale. XRD measurements showed more crystallized Hwangtoh clay in nano-dimension than that of raw material with crystallite sizes (t) of 108.52 and 126.7 nm, respectively. SEM (scanning electron microscope) measurements showed that the dispersed Si–PS hybrid nanocomposite had a D h of ~350 nm within the PET matrix. FTIR (Fourier transform infrared spectroscopy) measurements exhibited the characteristic absorption peaks of Si–O–Si stretching vibrations and Al–O–Si bending vibrations from both the Si–PS hybrid structure and PET/Si–PS composite. X-ray diffraction (XRD) measurements exhibited a characteristic Si diffraction peak of 2θ value at 25° and 29°, both from Si–PS hybrid nanoparticles and PET/Si–PS composites. The blending of PET with a Si–PS nanocomposite was determined by XPS (X-ray photoelectron spectroscopy) analysis, which showed three distinctive peaks representing the interatomic bonding of carbon. In XPS measurements, the decomposition of the Si 2p core peak demonstrated that the Si atom from Hwangtoh clay is composed of four chemical states such as Si0, Si+ (Si2O), Si2+ (SiO), and Si3+ (Si2O3). Our results provide evidence of the successful encapsulation of silicate from Hwangtoh clay in a PS shell, and further blending with PET by the melting extrusion method.
- Published
- 2017
12. Korean ICT Export to China, Japan, and the United States
- Author
-
Wan Joong Kim
- Subjects
Microbiology (medical) ,Economic growth ,Information and Communications Technology ,Political science ,Immunology ,Immunology and Allergy ,China - Published
- 2017
13. Solution-processed Au–Ag core–shell nanoparticle-decorated yarns for human motion monitoring
- Author
-
Yong Ju Yun, Yongseok Jun, Chil Seong Ah, Hyung Ju Park, and Wan Joong Kim
- Subjects
Materials science ,General Chemical Engineering ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,Nanoparticle ,Wearable computer ,Nanotechnology ,02 engineering and technology ,General Chemistry ,Wearable systems ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Human motion ,01 natural sciences ,0104 chemical sciences ,Solution processed ,Core shell ,0210 nano-technology ,ComputingMethodologies_COMPUTERGRAPHICS - Abstract
Wearable strain sensors based on Au–Ag core–shell nanoparticle decorated yarns were fabricated by a solution-based approach. Smart wearable systems with our strain sensors that can monitor various human motions, including finger motion, marching and squatting, and transmit the information of human motion in real time to an LED light was demonstrated.
- Published
- 2017
14. Effect of Cymbidium Root Extracts on Oxidative Stress-induced Myoblasts Damage
- Author
-
J. Opitz, Han Sung Kim, Tack-Joong Kim, Wan Joong Kim, and Kazuya Kabayama
- Subjects
Engineering ,Medical device ,business.industry ,Health science ,Botany ,Library science ,business - Abstract
Wan Joong Kim 1 , Han-Sung Kim 2 , Joerg Opitz 3 , Kazuya Kabayama 4 and Tack-Joong Kim 1 * Division of Biological Science and Technology, Yonsei-Fraunhofer Medical Device Lab, College of Science and Technology, Yonsei University, Wonju 220-710, Korea Department of Biomedical Engineering, Yonsei-Fraunhofer Medical Device Lab, College of Health Science, Yonsei University, Wonju 220-710, Korea Fraunhofer Institute for Ceramic Technologies and Systems-Material Diagnostics, Dresden, Germany Department of Chemistry, Graduate School of Science, Osaka University, Osaka, Japan
- Published
- 2014
15. Sensitive 'capillary ELISA' via vapor-phase surface modification
- Author
-
Bong Kyu Kim, Young Jun Kim, Hyo Young Cho, Chul Huh, Wan-Joong Kim, Sangwon Byun, Seok Hwan Hyun, and Kwang Hyo Chung
- Subjects
Chromatography ,Chemistry ,Capillary action ,Field emission scanning electron microscopy ,Optical detector ,010401 analytical chemistry ,Detector ,Vapor phase ,Metals and Alloys ,Analytical chemistry ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Colloidal gold ,Materials Chemistry ,Surface modification ,Amine gas treating ,Electrical and Electronic Engineering ,0210 nano-technology ,Instrumentation - Abstract
Sensitive ELISA for C-reactive protein (CRP) was performed in a capillary tube based on simple vapor-phase surface chemistry. Amine surfaces were produced in capillary tubes in two different methods using 3-aminopropyltriethoxysilane (APTES) in liquid and vapor phases. Those amine surfaces were tethered with gold nanoparticles (AuNPs) to be characterized by field emission scanning electron microscopy (FE-SEM) resulting in more dense and dispersed AuNP populations from the vapor-phase surface. Feasibility of a miniaturized home-made optical detector for “capillary ELISA” was performed by infusing into capillary tubes the colored solutions that had just gone through ELISA on a 96-well plate. The compatibility of the two results obtained from ELISAs on a well-plate and in capillary tubes, confirmed dependability of the miniaturized detector. Finally “capillary ELISA” was performed on the home-made detector using anti-CRP immobilized capillary tubes that had been prepared via vapor-phase surface treatment, resulting in detectability of 1.0 ng/mL of CRP, which turned out to be around 10 times higher in sensitivity than that of the well-plate ELISA.
- Published
- 2016
16. A Study on the Determinants of Corporate Cash Reserves and Marginal Value
- Author
-
Wan-Joong Kim and Soo-Jung Kim
- Subjects
Finance ,business.industry ,media_common.quotation_subject ,Cash flow forecasting ,Terminal value ,Operating cash flow ,Cash ,Economics ,Cash flow statement ,Cash on cash return ,Price/cash flow ratio ,business ,Cash management ,media_common - Published
- 2016
17. Bakanae Disease Reduction Effect by Use of Silicate Coated Seed in Wet Direct-Seeded Rice
- Author
-
Wan Joong Kim, Ki-Hong Jung, Ul-Su Choi, Yeon-Ju Kim, and Yang-Soon Kang
- Subjects
0106 biological sciences ,integumentary system ,biology ,Chemistry ,Inoculation ,fungi ,food and beverages ,Humidity ,biology.organism_classification ,01 natural sciences ,Silicate ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,nervous system ,Agronomy ,Seedling ,Bakanae ,Seeding ,tissues ,Mycelium ,010606 plant biology & botany ,Panicle - Abstract
To investigate the effect of soluble silicate zeolite dressing of the rice against bakanae disease, field trial in reclaimed land and in vitro were carried out. The coated rice seeds (SCS) which were dressed with the mixture of 25% silicic acids (binder), and the zeolite (coating powder). In wet direct seeding, uniform scattering of rice seeds on the soil surface and the better seedling establishment were shown in SCS treatment plots. The incidence of bakanae disease began from the mid tillering stage toward the heading stage. Around heading stage, the ratio of infected tillers reached its highest point by 9.9% in non-SCS treatment plots. While, in SCS treatment plots, the ratio of infected tillers was no more than 0.01%. The vitality of the pathogenic fungi of bakanae disease in the SCS and non-SCS samples were assessed. Samples were incubated for one week keeping proper humidity at after inoculated with panicles of infected rice plants from experimental field plots. In non-SCS treatment, pinkish colonies were formed on the grain surface of panicle of infected plants, and mycelium, macro-conidia and micro-conidia were developed actively inside part of infected grain inoculated. While in SCS treatment, micro-conidia and mycelium were not survived and the growth of macro-conidia, mycelia were greatly inhibited and withered. Based on the results, it is concluded that the environmental friendly control of bakanae disease by use of SCS is possible and soluble silicate can be applied as agents for replacement of seed disinfection.
- Published
- 2016
18. Effects ofCymbidiumRoot Ethanol Extract on Atopic Dermatitis
- Author
-
Tack-Joong Kim, Myung-Hun Lee, Sunyoung Kim, Seo Ho Kim, Wan-Joong Kim, and Hae-Sim Cha
- Subjects
0301 basic medicine ,Article Subject ,MAP kinase kinase kinase ,biology ,business.industry ,Syk ,lcsh:Other systems of medicine ,lcsh:RZ201-999 ,Immunoglobulin E ,medicine.disease_cause ,Proinflammatory cytokine ,03 medical and health sciences ,030104 developmental biology ,Complementary and alternative medicine ,Antiallergic agent ,Allergic response ,Immunology ,biology.protein ,Medicine ,business ,Protein kinase A ,Protein kinase B ,Research Article - Abstract
Cymbidiumhas known antibacterial and antiedema activity and has been used as an ingredient in cosmetics and fragrances. The effects ofCymbidiumethanol extract (CYM) on allergic response and the underlying mechanisms of action have not been reported. Therefore, the purpose of this study was to determine the effect of CYM on allergic responses. Topical application of CYM was effective against immunoglobulin E (IgE)/dinitrophenyl-conjugated bovine serum albumin- (DNP-BSA-) induced degranulation of RBL-2H3 cells and anaphylaxis in ICR mice. An allergic dermatitis-like mouse model was used to evaluate the therapeutic potential of CYMin vivo.Continuous application of 2,4-dinitrochlorobenzene (DNCB) not only induced dermatitis in ICR mice but also aggravated the skin lesioning. However, the application of CYM decreased skin lesion severity, scratching behavior, and IgE levels. In addition, CYM downregulated the expression of the proinflammatory cytokines interleukin- (IL-) 4, IL-13, and tumor necrosis factor- (TNF-)α. Studies of signal transduction pathways showed that CYM suppressed the phosphorylation of spleen tyrosine kinase (Syk), an upstream molecule. It also inhibited the phosphorylation of Akt, phospholipase C- (PLC-)γ, and mitogen-activated protein kinase kinase kinase (MEKK). These results indicate that CYM may be effective in preventing and reducing allergic response and may have therapeutic potential as an antiallergic agent in disorders such as atopic dermatitis.
- Published
- 2016
19. A Monolithic Silicon Nanocrystal Photonic Transducer for a Real-time Biomarker Detection
- Author
-
Chul Huh, Wan-Joong Kim, Jae Gab Lim, Joo Yong Sim, and Bong-Kyu Kim
- Subjects
Photocurrent ,Materials science ,business.industry ,Analytical chemistry ,Photodetector ,02 engineering and technology ,General Medicine ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Transducer ,Nanocrystal ,Colloidal gold ,Attenuated total reflection ,Optoelectronics ,Photonics ,Surface plasmon resonance ,0210 nano-technology ,business ,Engineering(all) - Abstract
We demonstrate the monolithic Si nanocrystal (NC) photonic transducer for a real-time protein detection. The monolithic photonic transducer was composed of the Si NC light-emitting diode (LED), Si NC photodetector (PD), and Si nitride (SiNx) optical waveguide that was optically self-aligned to the LED and PD. The Si NCs used as the fabrication of LED and PD were synthesized in the SiNx matrix. Antibodies were immobilized onto the surface of SiNx optical waveguide of the photonic transducer through self-assembled monolayers and surface aldehyde formation. Colloidal gold (Au) nanoparticles (NPs) were used to amplify the optical signal due to the strong surface plasmon resonance. The binding reaction of the Au NPs with the immobilized antibodies within the evanescent field at the transducer surface of the SiNx optical waveguide causes attenuated total reflection of the waveguided modes and thus reduction of the PD photocurrent. The detection limit of prostate-specific antigen (PSA) was around 1 ng/mL.
- Published
- 2016
- Full Text
- View/download PDF
20. Highly sensitive detection of cardiac troponin I in human serum using gold nanoparticle-based enhanced sandwich immunoassay
- Author
-
Bong Kyu Kim, Wan-Joong Kim, Hyo Young Cho, Young Jun Kim, Ansoon Kim, Kwang Hyo Chung, Chul Huh, and Chang-Geun Ahn
- Subjects
Chromatography ,biology ,Chemistry ,Metals and Alloys ,Nanoparticle ,Immunogold labelling ,Condensed Matter Physics ,Molecular biology ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Highly sensitive ,Silver stain ,Antigen ,Colloidal gold ,Troponin I ,cardiovascular system ,Materials Chemistry ,biology.protein ,Electrical and Electronic Engineering ,Antibody ,Instrumentation - Abstract
We have developed an enhanced sandwich immunogold assay for highly sensitive detection of cardiac troponin I (cTnI) in human serum. In this assay, the immunoreaction undergoes in sample solution between cTnI antigen and gold nanoparticles conjugated with detection antibodies of cTnI (immunogolds). Then, a capture antibody of cTnI immobilized on a standard 96-well plate captures the immunogold complex, followed by silver staining of the immunogold for the purpose of signal amplification. Compared to the direct assay where the immunoreaction occurs between the target and the capture antibody coated on the well, we found the enhanced assay shows greatly improved sensitivity by two orders of magnitude and a linear relation of the quantitative plot. Because the immunogold concentration affect greatly the sensitivity of the cTnI detection, we also studied the performance of direct and enhanced immunogold assay depending on the concentration of immunogold conjugates. By using the enhanced assay with the optimized procedure, we could achieve the detection of cTnI in human serum as low as 15 pg/mL. We also verified the enhanced immunogold assay by measuring the concentration of clinical samples for a healthy person and patients. This development can allow us to apply the assay not only for the analysis of other cardiac markers as well as disease-related biomarkers but also for the optimization of other chip-based silver enhanced colorimetric sensors.
- Published
- 2015
21. Preparation and Characterization of a Triple Layered Au-PMMA-PbSe Hybrid Nanocomposite: Manipulation of PMMA Spacer Layer by Oxygen Plasma Etching
- Author
-
Ae Rhan Kim, Jae Bong Choi, Dong Jin Yoo, Wan-Joong Kim, and Sanghee Kim
- Subjects
chemistry.chemical_classification ,Nanocomposite ,Materials science ,Nanoparticle ,Nanotechnology ,General Chemistry ,Polymer ,chemistry.chemical_compound ,chemistry ,X-ray photoelectron spectroscopy ,Quantum dot ,Etching (microfabrication) ,Composite material ,Layer (electronics) ,Lead selenide - Abstract
A hybrid triple-layered nanocomposite structure of plasmonic gold (Au), polymethylmethacrylate (PMMA), and lead selenide (PbSe) quantum dot (QD) on quartz substrate was developed. The fabricated nanocomposite exhibited well-established triple-layered morphology (Au-PMMA-QD on quartz), but had different coupling distances between Au, on the bottom, and PbSe QD, on the top. Control of the coupling distances in terms of different thicknesses of a PMMA spacer layer was examined by etching for different durations, from 7 to 30 min. The corresponding thicknesses of the PMMA layer ranged from ~3.8 to ~88 nm at an etching rate of 2 nm/min. Atomic force microscopy measurements showed that the well-established triple-layered hybrid nanocomposite structure had the heights of ~15 nm (Au) and ~4 nm (PbSe QD). X-ray photoelectron spectroscopy results revealed the characteristic peaks assigned to each nanoparticle and polymer layer. The results illustrated the triple-layered structures with different PMMA spacer layers, with no cross interference between the layers.
- Published
- 2015
22. A simple PAN-based fabrication method for microstructured carbon electrodes for organic field-effect transistors
- Author
-
Jae-Hak Choi, Chan-Hee Jung, Chang-Hee Jung, Dong-Yu Kim, Dongyoon Khim, In-Tae Hwang, Jae-Suk Lee, Bon-Cheol Ku, and Wan-Joong Kim
- Subjects
Materials science ,Fabrication ,Organic field-effect transistor ,Carbonization ,Polyacrylonitrile ,Nanotechnology ,General Chemistry ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,Electrode ,Surface roughness ,General Materials Science ,Wafer ,Thin film - Abstract
Facile and efficient fabrication of polyacrylonitrile (PAN)-based conductive graphitic carbon microstructures (GCMs) and their application to the electrodes of organic field-effect transistors (OFETs) is described. The PAN thin films spin-coated on a SiO 2 -deposited Si wafer was irradiated through a pattern mask with 150 keV H + ions at various fluences, and subsequently developed to form PAN microstructures. The resulting PAN microstructures were carbonized at various temperatures to create the GCMs. The analytical results revealed that the optimized fluence and carbonization temperature for well-defined GCMs was 3 × 10 15 ions cm −2 and 100 °C, respectively, and that the resulting GCMs created at the optimized condition exhibited a greatly low surface roughness of 0.36 nm, a good electrical conductivity of about 600 S cm −1 , and a high work function of 5.11 eV. Noticeably, the GCM electrodes-based p-type OFET showed a comparable performance to that of the gold electrode-based one, demonstrating that the practical use of GCMs as cheap electrodes to replace expensive metallic ones for organic electronic devices.
- Published
- 2015
23. Transition of graphene oxide-coated fiber bundles from insulator to conductor by chemical reduction
- Author
-
Suyong Jung, Wan Joong Kim, Yongseok Jun, Daehee Kim, Ho Jong Kim, Dong Han Ha, Yong Ju Yun, and Sam Nyung Yi
- Subjects
chemistry.chemical_classification ,Materials science ,Graphene ,Mechanical Engineering ,Metals and Alloys ,Oxide ,Nanotechnology ,Insulator (electricity) ,Polymer ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,law.invention ,Conductor ,Polyester ,symbols.namesake ,chemistry.chemical_compound ,Electrical resistance and conductance ,chemistry ,Mechanics of Materials ,law ,Materials Chemistry ,symbols ,Composite material ,Raman spectroscopy - Abstract
We fabricate graphene oxide (GO)-coated fiber bundles via electrostatic deposition of GO sheets on polyester/cotton fiber bundles and investigate the changes in their properties by chemical reduction in a hydroiodic acid solution. The structural properties of GO sheets change rapidly upon exposure to reduction agents but remain under a high defect density regime after the reduction. The electrical resistance of the fiber bundles decreases logarithmically for the first minute of the reduction. In contrast to the structural property, a longer chemical reduction over tens of minutes deteriorates the electrical property. The effect of chemical reduction on the electrical conductance of GO-coated fiber bundles is discussed based on the competition of various factors, such as the number of conducting pathways and the carrier density, among others.
- Published
- 2015
24. Synergistic Use of Gold Nanoparticles (AuNPs) and 'Capillary Enzyme-Linked Immunosorbent Assay (ELISA)' for High Sensitivity and Fast Assays
- Author
-
Bongjin Jeong, Sangwon Byun, Hyo Young Cho, Young Jun Kim, Jae-Doo Huh, and Wan-Joong Kim
- Subjects
Capillary action ,Metal Nanoparticles ,Enzyme-Linked Immunosorbent Assay ,02 engineering and technology ,Conjugated system ,Optical density ,lcsh:Chemical technology ,01 natural sciences ,Biochemistry ,Horseradish peroxidase ,Antibodies ,Article ,Analytical Chemistry ,Absorbance ,capillary ELISA ,ImmunoGold conjugate ,C-reactive protein (CRP) ,point-of-care (POC) ,lcsh:TP1-1185 ,Electrical and Electronic Engineering ,Instrumentation ,Horseradish Peroxidase ,chemistry.chemical_classification ,Chromatography ,biology ,010401 analytical chemistry ,021001 nanoscience & nanotechnology ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Highly sensitive ,Enzyme ,chemistry ,Colloidal gold ,biology.protein ,Gold ,0210 nano-technology - Abstract
Using gold nanoparticles (AuNPs) on “capillary enzyme-linked immunosorbent assay (ELISA)”, we produced highly sensitive and rapid assays, which are the major attributes for point-of-care applications. First, in order to understand the size effect of AuNPs, AuNPs of varying diameters (5 nm, 10 nm, 15 nm, 20 nm, 30 nm, and 50 nm) conjugated with Horseradish Peroxidase (HRP)-labeled anti-C reactive protein (antiCRP) (AuNP•antiCRP-HRP) were used for well-plate ELISA. AuNP of 10 nm produced the largest optical density, enabling detection of 0.1 ng/mL of CRP with only 30 s of incubation, in contrast to 10 ng/mL for the ELISA run in the absence of AuNP. Then, AuNP of 10 nm conjugated with antiCRP-HRP (AuNP•antiCRP-HRP) was used for “capillary ELISA” to detect as low as 0.1 ng/mL of CRP. Also, kinetic study on both 96-well plates and in a capillary tube using antiCRP-HRP or AuNP•antiCRP-HRP showed a synergistic effect between AuNP and the capillary system, in which the fastest assay was observed from the “AuNP capillary ELISA”, with its maximum absorbance reaching 2.5 min, while the slowest was the typical well-plate ELISA with its maximum absorbance reaching in 13.5 min.
- Published
- 2017
25. Sensitivity response to coating material thickness for an optical resonant reflective biosensor based on a guided mode resonance filter
- Author
-
Won Ick Jang, Chul Huh, Hyunsung Ko, Sun-Hee Park, Bong Kyu Kim, Jongcheol Hong, Wan-Joong Kim, Soo Jun Park, Kyung-Hyun Kim, and Gun Yong Sung
- Subjects
Materials science ,business.industry ,High-refractive-index polymer ,Guided-mode resonance ,technology, industry, and agriculture ,Biomedical Engineering ,Analytical chemistry ,Physics::Optics ,Bioengineering ,macromolecular substances ,Grating ,engineering.material ,Waveguide (optics) ,Laser linewidth ,Coating ,engineering ,Optoelectronics ,Electrical and Electronic Engineering ,business ,Biosensor ,Refractive index ,Biotechnology - Abstract
Sensitivity is a very important parameter for biosensor applications. We have numerically and experimentally studied the sensitivity and linewidth responses of optical resonant reflective biosensors to the thickness of high refractive index materials coating the grating layer used to create a guided mode. Zero sensitivity, which may create serious problems in biosensors, is obtained when the coating material has a relatively low refractive index and a thin coating thickness (near the cutoff condition in which a high index layer is no longer capable of acting as a waveguide). The sensitivity and linewidth are greatly influenced by the thickness of the coating material. The thickness also has an optimal state, which is a very important factor for designing highly sensitive optical resonant reflective biosensors using a guided mode resonance filter.
- Published
- 2014
26. Colorimetric quantitative sensing of alkali metal ions based on reversible assembly and disassembly of gold nanoparticles
- Author
-
Wan Soo Yun, Chil Seong Ah, Sang-Woo Joo, and Wan-Joong Kim
- Subjects
Ionic radius ,Chemistry ,Inorganic chemistry ,General Physics and Astronomy ,Nanoparticle ,Alkali metal ,Ion ,Metal ,Colloid ,Colloidal gold ,Color changes ,visual_art ,visual_art.visual_art_medium ,General Materials Science - Abstract
A novel and simple method for the colorimetric quantitative sensing of individual alkali metal ions (Li + , Na + , K + , and Rb + ) based on the reversible properties of self-assembled aggregates and individual gold nanoparticles (Au NPs) is described. This paper demonstrates reversible self-assembly processes where the degree of assembly and disassembly is dependent on the individual alkali metal ion concentration, nanoparticle size, and alkali metal ionic radii. The color changes of the colloidal Au NPs with metal ion concentrations in colloidal NP solutions occur reversibly. Below a certain concentration of alkali metal ions, the aggregates of Au NPs are redispersed. As the Au NP diameters and the alkali metal ionic radii increase, the critical concentration decreases.
- Published
- 2013
27. Cell patterning on poly(sodium 4-styrenesulfonate)-patterned fluoropolymer substrate
- Author
-
Sung-Kwon Hong, Chang-Hee Jung, In-Tae Hwang, Jae-Hak Choi, Wan-Joong Kim, and Chan-Hee Jung
- Subjects
Nuclear and High Energy Physics ,Materials science ,Sodium ,chemistry.chemical_element ,Substrate (chemistry) ,Adhesion ,Vinyl ether ,stomatognathic diseases ,chemistry.chemical_compound ,chemistry ,Polymerization ,Polymer chemistry ,medicine ,Surface modification ,Fluoropolymer ,Wetting ,Instrumentation ,medicine.drug - Abstract
The surface functionalization of bio-inert fluoropolymer films through ion beam-induced surface graft polymerization was investigated to control the cellular behavior. The surface of poly(tetrafluoroethylene-co-perfluoropropl vinyl ether) (PFA) films was selectively activated by 150 keV H + ion implantation in the presence of a pattern mask and sodium 4-styrenesulfonate (SS) was then graft polymerized onto the implanted PFA films to form hydrophilic poly(sodium 4-styrenesulfonate) (PSS)-patterned PFA films. The surface of the resulting PSS-patterned PFA films was investigated in terms of the degree of graft polymerization, chemical structure, chemical composition, wettability, and morphology. The analytical results revealed that PSS was selectively grafted onto the implanted regions of the PFA films. Furthermore, in vitro cell culture on the PSS-patterned PFA films exhibited a preferential adhesion and growth of cells onto the PSS-grafted regions, resulting in well-organized 100 μm cell patterns.
- Published
- 2013
28. Direct Detection System for Escherichia coli Using Au–Ag Alloy Microchips
- Author
-
Sanghee Kim, Ae Rhan Kim, Wan-Joong Kim, and Dong Jin Yoo
- Subjects
Aqueous solution ,Materials science ,Scanning electron microscope ,General Chemical Engineering ,Alloy ,technology, industry, and agriculture ,Analytical chemistry ,Nanoparticle ,General Chemistry ,engineering.material ,equipment and supplies ,medicine.disease_cause ,Industrial and Manufacturing Engineering ,chemistry.chemical_compound ,Sodium borohydride ,chemistry ,Silanization ,Sodium citrate ,medicine ,engineering ,Escherichia coli ,Nuclear chemistry - Abstract
Au–Ag alloy nanoparticles (NPs) were prepared by the reduction of metal ion mixtures in aqueous sodium citrate solution using sodium borohydride (NaBH4). The resulting Au–Ag alloy NPs were analyzed by various techniques. Alloy-attached chips for the detection of microorganisms were fabricated simply by the attachment of Au–Ag alloy nanoparticles onto glass slides after silanization through self-assembled monolayers (SAMs) for the formation of activated amine (−NH2) as a terminal function group. The alloy-attached chips were investigated for their ability to bind the target Escherichia coli (E. coli) in water. E. coli was detected in water as a function of time and concentration by UV–vis spectroscopic measurements based on the interaction between the alloy-attached chip and E. coli. Field-emission scanning electron microscopy (FE-SEM) was used to directly observe the E. coli captured on the alloy chips. These studies demonstrated that E. coli in drinking water can be directly detected with Au–Ag alloy mic...
- Published
- 2013
29. Photo selective protein immobilization using bovine serum albumin
- Author
-
Jongcheol Hong, Chil Seong Ah, Chan Woo Park, Chul Huh, Wan-Joong Kim, Bong Kyu Kim, Jong-Heon Yang, Yo Han Choi, Kwang Hyo Chung, Ansoon Kim, and Gun Yong Sung
- Subjects
Materials science ,Chromatography ,biology ,General Physics and Astronomy ,Substrate (chemistry) ,Surfaces and Interfaces ,General Chemistry ,Condensed Matter Physics ,Surfaces, Coatings and Films ,chemistry.chemical_compound ,chemistry ,Ellipsometry ,Diazirine ,biology.protein ,Fluorescence microscope ,Molecule ,Bovine serum albumin ,Bifunctional ,Protein adsorption - Abstract
A simple and selective technique which immobilizes protein onto a solid substrate by using UV illumination has been developed. In protein immobilization, a Bovine serum albumin (BSA) performed bifunctional role as a cross-linker between substrate and proteins and as a blocker inhibiting a nonspecific protein adsorption. A new photo-induced protein immobilization process has been investigated at each step by fluorescence microscopy, ellipsometry, and Fourier transform infrared (FT-IR) spectroscopy. A UV photomask has been used to induce selective protein immobilization on target regions of the surface of the SiO2 substrates under UV illumination with negligible nonspecific binding. The UV illumination also showed improved photostability than the conventional methods which employed bifunctional photo-crosslinker molecules of photo-reactive diazirine. This new UV illumination-based photo-addressable protein immobilization provides a new approach for developing novel protein microarrays for multiplexed sensing as well as other types of bio-immobilization in biomedical devices and biotechnologies.
- Published
- 2012
30. Plasmon-Coupled CdSe/ZnS and CdTe/CdS/ZnS Coreshells for Hybrid Light Emitting Devices
- Author
-
Quinton Rice, Anderson Hayes, Sungsoo Jung, Andrew Wang, Hyoyoung Cho, Wan-Joong Kim, William Yu, Mahmoud Abdel-Fattah, Bagher Tabibi, and Jaetae Seo
- Subjects
Materials science ,Condensed Matter::Other ,business.industry ,Band gap ,Exciton ,Biomedical Engineering ,Physics::Optics ,Bioengineering ,General Chemistry ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Condensed Matter Physics ,Cadmium telluride photovoltaics ,law.invention ,Condensed Matter::Materials Science ,Quantum dot ,law ,Energy level ,Optoelectronics ,General Materials Science ,business ,Plasmon ,Visible spectrum ,Light-emitting diode - Abstract
Plasmon-coupled CdSe/ZnS and CdTe/CdS/ZnS coreshells are investigated for their optoelectronic applications because of their high color purity, wide optical tunability, large PL enhancement, and compact and easy integration into electronic devices. The quantum confinement of carriers within quantum dots (QDs) with sizes near the exciton Bohr radius (CdSe ~ 5.8 nm, CdTe ~ 7 nm) exhibits the features of discrete energy states and blue-shift from the bulk bandgap (CdSe ~718 nm, CdTe ~ 863 nm) in the optical spectrum. While the fluorescence from the QDs is attributable to the exciton carrier recombination, large PL enhancement and fast emission time is achieved through plasmon-exciton coupling via the Coulomb interaction. Large PL enhancement of QDs in the vicinity of plasmonic particles was observed and attributed to the reduction of the non-radiative decay rate and large local field enhancement. The large PL enhancement and wide optical tunability along with high color purity from plasmon-coupled QDs enables the realization of hybrid LEDs.
- Published
- 2016
31. Inhibitory effect of Pterocarpus indicus Willd water extract on IgE/Ag-induced mast cell and atopic dermatitis-like mouse models
- Author
-
Hae-Sim Cha, Sunyoung Kim, Myung-Hun Lee, Kwang-Ho Lee, Seo Ho Kim, Tack-Joong Kim, and Wan-Joong Kim
- Subjects
0301 basic medicine ,Male ,MAP Kinase Kinase 4 ,Syk ,Immunoglobulin E ,medicine.disease_cause ,Applied Microbiology and Biotechnology ,Biochemistry ,Cell Degranulation ,Analytical Chemistry ,Mice ,0302 clinical medicine ,Anti-Allergic Agents ,Dinitrochlorobenzene ,Mast Cells ,Phosphorylation ,Skin ,Mitogen-Activated Protein Kinase 1 ,Mice, Inbred ICR ,Mitogen-Activated Protein Kinase 3 ,biology ,Chemistry ,Degranulation ,General Medicine ,Atopic dermatitis ,Mast cell ,medicine.anatomical_structure ,Antiallergic agent ,Allergic response ,Irritants ,Biotechnology ,Signal Transduction ,Pterocarpus ,Dermatitis, Atopic ,03 medical and health sciences ,medicine ,Animals ,Syk Kinase ,Molecular Biology ,Phospholipase C gamma ,Plant Extracts ,Organic Chemistry ,Water ,medicine.disease ,Disease Models, Animal ,030104 developmental biology ,Gene Expression Regulation ,Immunology ,biology.protein ,Proto-Oncogene Proteins c-akt ,030215 immunology - Abstract
Pterocarpus indicus Willd has been widely used as a traditional medicine to treat edema, cancer, and hyperlipidemia, but its antiallergic properties and underlying mechanisms have not yet been studied. The purpose of this study was to evaluate the antiallergic activity of Pterocarpus indicus Willd water extract (PIW) using activated mast cells and an atopic dermatitis (AD)-like mouse model. PIW decreased IgE/Ag-induced mast cell degranulation and the phosphorylation of Syk and downstream signaling molecules such as PLC-γ, Akt, Erk 1/2, JNK compared to stimulated mast cells. In DNCB-induced AD-like mice, PIW reduced IgE level in serum, as well as AD-associated scratching behavior and skin severity score. These results indicate that PIW inhibits the allergic response by reducing mast cell activation and may have clinical potential as an antiallergic agent for disorders such as AD.
- Published
- 2016
32. Coptis japonica Makino extract suppresses angiogenesis through regulation of cell cycle-related proteins
- Author
-
Seo Ho Kim, Eok-Cheon Kim, Sunyoung Kim, Myung-Hun Lee, Tack-Joong Kim, and Wan-Joong Kim
- Subjects
0301 basic medicine ,Male ,Vascular Endothelial Growth Factor A ,Cyclin E ,Cell cycle checkpoint ,Angiogenesis ,Cell Survival ,Cyclin D ,Angiogenesis Inhibitors ,Applied Microbiology and Biotechnology ,Biochemistry ,Analytical Chemistry ,Neovascularization ,Rats, Sprague-Dawley ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Cell Movement ,medicine ,Human Umbilical Vein Endothelial Cells ,Animals ,Humans ,Molecular Biology ,Cell Proliferation ,Tube formation ,biology ,Neovascularization, Pathologic ,Plant Extracts ,Organic Chemistry ,Cyclin-Dependent Kinase 2 ,Cyclin-Dependent Kinase 4 ,General Medicine ,Cell cycle ,G1 Phase Cell Cycle Checkpoints ,Cell biology ,Rats ,Vascular endothelial growth factor ,030104 developmental biology ,chemistry ,Gene Expression Regulation ,030220 oncology & carcinogenesis ,Immunology ,biology.protein ,medicine.symptom ,Biotechnology ,Coptis - Abstract
Angiogenesis, neovascularization from pre-existing vessels, is a key step in tumor growth and metastasis, and anti-angiogenic agents that can interfere with these essential steps of cancer development are a promising strategy for human cancer treatment. In this study, we characterized the anti-angiogenic effects of Coptis japonica Makino extract (CJME) and its mechanism of action. CJME significantly inhibited the proliferation, migration, and invasion of vascular endothelial growth factor (VEGF)-stimulated HUVECs. Furthermore, CJME suppressed VEGF-induced tube formation in vitro and VEGF-induced microvessel sprouting ex vivo. According to our study, CJME blocked VEGF-induced cell cycle transition in G1. CJME decreased expression of cell cycle-regulated proteins, including Cyclin D, Cyclin E, Cdk2, and Cdk4 in response to VEGF. Taken together, the results of our study indicate that CJME suppresses VEGF-induced angiogenic events such as proliferation, migration, and tube formation via cell cycle arrest in G1.
- Published
- 2016
33. Detection of uncharged or feebly charged small molecules by field-effect transistor biosensors
- Author
-
Joon Sung Lee, Wan-Joong Kim, Gun Yong Sung, Jong-Heon Yang, Kwang Hyo Chung, Chan Woo Park, Chil Seong Ah, Yo Han Choi, Jungho Kim, and In Bok Baek
- Subjects
Aflatoxin B1 ,Transistors, Electronic ,Chemistry ,Transistor ,Biomedical Engineering ,Biophysics ,Analytical chemistry ,Metal Nanoparticles ,Ionic bonding ,Nanoparticle ,Biosensing Techniques ,General Medicine ,Ochratoxins ,Small molecule ,law.invention ,Isoelectric point ,law ,Electrochemistry ,Zearalenone ,Molecule ,Field-effect transistor ,Gold ,Biosensor ,Biotechnology - Abstract
This paper describes a new technique for the detection of uncharged or feebly charged small molecules (
- Published
- 2012
34. Bio-functionalized Gold Nanoparticles for Surface-Plasmon- Absorption-Based Protein Detection
- Author
-
Young-S. Rho, Dong-Jin Yoo, Wan-Joong Kim, and Soo-Hee Choi
- Subjects
chemistry.chemical_classification ,Streptavidin ,biology ,Absorption spectroscopy ,Chemistry ,Biomolecule ,Nanotechnology ,General Chemistry ,Combinatorial chemistry ,chemistry.chemical_compound ,Biotin ,Colloidal gold ,Biotinylation ,biology.protein ,Biosensor ,Avidin - Abstract
Bio-functionalized gold nanoparticles (AuNPs), which bio-specifically interact with biotin-(strept)avidin, were investigated in this study. AuNPs were functionalized with a synthetically-provided biotin-linked thiol (BLT), which was synthesized by amidation of the active ester of biotin with 2-mercaptoethylamine. The BLT-attached AuNP was bio-specific for streptavidin, making it potentially useful for biosensor applications. To test the bio-specific interactions, the colors, absorption spectra and TEM images were investigated for proteins such as streptavidin, cytochrome C, myoglobin and hemoglobin. The colors and absorption spectra changed when streptavidin was added to the BLT-attached AuNP solution. However, the color and spectra did not change when the other proteins were added to the same solution. These results show that the AuNPs provided a colloidal solution with excellent stability and highly selective absorption characteristics for streptavidin as a target molecule. Proteins were also screened in order to identify a general strategy for the use of optical biosensing proteins based on AuNPs. In addition, TEM images confirmed that streptavidin led the BLT-attached AuNPs to aggregate or precipitate.
- Published
- 2011
35. Plasmon coupling of R6G-linked gold nanoparticle assemblies for surface-enhanced Raman spectroscopy
- Author
-
Jaetae Seo, Wan-Joong Kim, Maria Veronica Rigo, and Sungsoo Jung
- Subjects
Materials science ,business.industry ,Analytical chemistry ,Nanoparticle ,Surface-enhanced Raman spectroscopy ,Rhodamine 6G ,symbols.namesake ,Wavelength ,chemistry.chemical_compound ,chemistry ,symbols ,Optoelectronics ,Surface plasmon resonance ,business ,Spectroscopy ,Raman scattering ,Excitation ,Localized surface plasmon - Abstract
This paper presents the study of surface-enhanced Raman scattering (SERS) for Rhodamine 6G (R6G)-linked gold (Au) assemblies. The nano-assemblies fabricated with Au nanoparticles, having diameters (D) of ∼5–40 nm, possessed interparticle gaps of ∼0.03–0.2D, respectively. The R6G-linked Au assemblies displayed weak spectral shifts of localized surface plasmon resonance (LSPR) mode at shorter wavelength region and large fractional red-shifts Δλ ∼ 0.07–0.47λo at longer wavelength region. The resonant spectral coupling of the nano-assemblies LSPR mode at the longer wavelength region and the optical excitation at ∼785 nm, in addition to the highly localized hot spots, could support the large SERS enhancement of R6G-linked Au assemblies.
- Published
- 2011
36. A Compact Tunable VCSEL and a Built-in Wavelength Meter for a Portable Optical Resonant Reflection Biosensor Reader
- Author
-
Jongcheol Hong, Ho-Jin Jang, Chul Huh, Gun Yong Sung, Kyung-Hyun Kim, Bong-Kyu Kim, Seon-Hee Park, Wan-Joong Kim, Hyunsung Ko, and Seong-Seok Yang
- Subjects
Materials science ,business.industry ,Guided-mode resonance ,Laser ,Atomic and Molecular Physics, and Optics ,Optical spectrometer ,law.invention ,Vertical-cavity surface-emitting laser ,Wavelength ,Optics ,law ,Photonics ,business ,Biosensor ,Tunable laser - Abstract
This study reports a portable and precision photonic biosensor reader that can measure the concentration of a particular antigen using an optical resonant reflection biosensor (ORRB). To create a compact biosensor reader, a compact tunable vertical-cavity surface-emitting laser (VCSEL) and a compact built-in wavelength meter were manufactured. The wavelength stability and accuracy of the compact built-in wavelength meter were measured to be less than 0.02 nm and 0.06 nm, respectively. The tunable VCSEL emission wavelength was measured with the compact built-in wavelength meter, it has a fast sweep time (~ 10 seconds) and a wide tuning range (> 4 nm) that are sufficient for biosensor applications based on ORRB. The reflection spectrum of a plastic based ORRB chip was measured by the fabricated portable photonic biosensor reader using the VCSEL and wavelength meter. Although the reader is the size of a palmtop device, it could make a precise measurement of the peak wavelength on equal terms with a conventional bulky optical spectrometer.
- Published
- 2010
37. Response to Cardiac Markers in Human Serum Analyzed by Guided-Mode Resonance Biosensor
- Author
-
Jongcheol Hong, Chil Seong Ah, Ansoon Kim, Junghan Song, Bong Kyu Kim, Seon Hee Park, Wan-Joong Kim, Sanghoon Song, Kyung-Hyun Kim, Gun Yong Sung, and Chul Huh
- Subjects
Detection limit ,Cardiac troponin ,Chromatography ,Immobilized enzyme ,Myoglobin ,Chemistry ,Photoelectron Spectroscopy ,Troponin I ,Immobilized Antibodies ,Biosensing Techniques ,Immunogold labelling ,Analytical Chemistry ,chemistry.chemical_compound ,Creatine Kinase, MB Form ,Humans ,Gold ,Antibodies, Immobilized ,Biosensor ,Biomarkers - Abstract
Cardiac markers in human serum with concentrations less than 0.1 ng/mL were analyzed by use of a guided-mode resonance (GMR) biosensor. Cardiac troponin I (cTnI), creatine kinase MB (CK-MB), and myoglobin (MYO) were monitored in the serum of both patients and healthy controls. Dose-response curves ranging from 0.05 to 10 ng/mL for cTnI, from 0.1 to 10 ng/mL for CK-MB, and from 0.03 to 1.7 μg/mL for MYO were obtained. The limits of detection (LOD) for cTnI, CK-MB, and MYO were less than 0.05, 0.1, and 35 ng/mL, respectively. Analysis time was 30 min, which is short enough to meet clinical requirements. Antibody immobilization and the hydrophilic properties of the guided-mode resonance filter (GMRF) surface were investigated by X-ray photoelectron spectroscopy (XPS) and by monitoring the peak wavelength shift and water contact angle (CA). Both assays used to evaluate the surface density of the immobilized antibodies, a sandwich enzyme-linked immunosorbent assay (ELISA) and a sandwich immunogold assay, showed that the antibodies were successfully immobilized and sufficiently aligned to detect the low concentration of biomarkers. Our results show that the GMR biosensor will be very useful in developing low-cost portable biosensors that can screen for cardiac diseases.
- Published
- 2010
38. Fabrication of a Nanosize Pattern Embedded Plastic Chip via an Injection Molding Method for Application to an Optical Biosensor
- Author
-
Hyunsung Ko, Gun Yong Sung, Wan-Joong Kim, Jung-Ki Hong, Bong-Kyu Kim, Chul Huh, and Kyuheon Kim
- Subjects
Fabrication ,Materials science ,Polymers and Plastics ,Polymethyl methacrylate ,General Chemical Engineering ,Nano ,Materials Chemistry ,Analytical chemistry ,Nanotechnology ,Optical biosensor ,Molding (process) ,Chip ,Industrial and Manufacturing Engineering - Abstract
We demonstrate a commercialized injection molding method for nano patterning of polymethyl methacrylate (PMMA) for the purpose of mass production of a label-free optical biosensor chip. Scanning electron microscope (SEM) images clearly show uniform nanopattern transfer on the plastic chip fabricated by an injection molding method. A uniformly deposited silicon nitride layer having a high refractive index by a plasma enhanced chemical vapor deposition (PECVD) technique is also observed. A unique characterization method is described wherein optical resonance reflection is used accurately and quickly to characterize the geometrical sensor structure. The authors anticipate that this robust method will provide an excellent means of producing an optical resonance reflection biosensor (ORRB).
- Published
- 2010
39. Electronic Detection of Biomarkers by Si Field-Effect Transistor from Undiluted Sample Solutions with High Ionic Strengths
- Author
-
Jong-Heon Yang, Chil Seong Ah, Chang-Geun Ahn, Gun Yong Sung, Tae-Youb Kim, Chan Woo Park, Ansoon Kim, Wan-Joong Kim, and In Bok Baek
- Subjects
Ionic strength ,Chemistry ,Phosphate buffered saline ,Analytical chemistry ,Ionic bonding ,Direct monitoring ,Field-effect transistor ,General Chemistry ,Biosensor ,Dilution - Abstract
In this study, we have developed a new detection method using Si field effect transistor (FET)-type biosensors, which enables the direct monitoring of antigen-antibody binding within very high-ionic-strength solutions such as 1×PBS and human serum. In the new method, as no additional dilution or desalting processes are required, the FET-type biosensors can be more suitable for ultrasensitive and real-time analysis of raw sample solutions. The new detection scheme is based on the observation that the strength of antigen-antibody-specific binding is significantly influenced by the ionic strength of the reaction solutions. For a prostate specific antigen (PSA), in some conditions, the binding reaction between PSA and anti-PSA in a low-ionic strength reaction solution such as 10 µM phosphate buffer is weak (reversible), while that in high-ionic strength reaction solutions such as 1×PBS or human serum is strong.
- Published
- 2010
40. Fabrication of Anionic Sulfate-Functionalized Nanoparticles as an Immunosensor by Protein Immobilization
- Author
-
Chil Seong Ah, Wan-Joong Kim, Ansoon Kim, Sungho Ko, Hyeon-Bong Pyo, and Sanghee Kim
- Subjects
Anions ,Surface Properties ,Analytical chemistry ,Emulsion polymerization ,Nanoparticle ,Antibodies ,Antigen-Antibody Reactions ,chemistry.chemical_compound ,X-ray photoelectron spectroscopy ,Electrochemistry ,Zeta potential ,Humans ,Bicinchoninic acid assay ,General Materials Science ,Particle Size ,Spectroscopy ,Immunoassay ,Sulfates ,Troponin I ,Models, Immunological ,Surfaces and Interfaces ,Potassium persulfate ,Condensed Matter Physics ,chemistry ,Immunoglobulin G ,Nanoparticles ,Polystyrenes ,Particle ,Polystyrene ,Nuclear chemistry - Abstract
Anionic sulfate (SO(4)(-))-functionalized polystyrene (PS) nanoparticles were prepared by the thermal decomposition of potassium persulfate (KPS) in the presence of sodium tetraborate via emulsion polymerization. The presence of a SO(4)(-) group at a solid/liquid interface of a particle surface was confirmed by a zeta potential value of -40.6 mV as well as the shifting of S 2p spectra toward a lower-binding-energy region around 162.7 eV (2p(3/2)) and 164.4 eV (2p(1/2)) in X-ray photoelectron spectroscopy (XPS) analysis. The electrostatic attraction between positively charged antibodies of human immunoglobulin G (hIgG) and cardiac troponin I (cTnI) and negatively charged particle surfaces was accomplished. The atomic force microscopy (AFM) measurement and bicinchoninic acid (BCA) assay results show binding structure between hIgG and antibodies of hIgG (anti-hIgG) with a gradual increase in particle diameter to 152.6 nm (bare), 170.2 nm (hIgG), and 178.9 nm (hIgG/anti-hIgG). Surface coverage densities of 331.4 ng/cm(2) (hIgG) and 320.3 ng/cm(2) (cTnI) and the binding capacity of hIgG to HyLite-750-labeled Fab-specific anti-hIgG (approximately 81.2%) indicate that the majority of hIgG was immobilized with a Y-shaped orientation. The sandwich immunoassay results provide the evidence that the immunological activity of cTnI on the PS nanoparticle surface was retained because the binding activity of the cTnI-PS nanoparticle/cTnI (antigen)/detection cTnI-antibody reaction showed a 5-fold higher activity than that of the cTnI-PS nanoparticle/human serum albumin (HSA)/detection cTnI antibody used as a negative control.
- Published
- 2010
41. Specific binding of streptavidin onto the nonbiofouling titanium/titanium oxide surface through surface-initiated, atom transfer radical polymerization and bioconjugation of biotin
- Author
-
Bong-Soo Lee, Wan Joong Kim, Sung Min Kang, Hyuk Jun Jung, Eu Gene Oh, Mun Jae Kil, and Insung S. Choi
- Subjects
chemistry.chemical_classification ,Materials science ,Polymers and Plastics ,Atom-transfer radical-polymerization ,General Chemical Engineering ,Organic Chemistry ,Inorganic chemistry ,technology, industry, and agriculture ,chemistry.chemical_element ,Polymer ,Polymer engineering ,Titanium oxide ,chemistry.chemical_compound ,chemistry ,Polymerization ,Polymer chemistry ,Materials Chemistry ,Surface modification ,Ethylene glycol ,Titanium - Abstract
Chemical modification of titanium/titanium oxide (Ti/TiO2) substrates has recently gained a great deal of attention because of the applications of Ti/TiO2-based materials to biomedical areas. The reported modification methods generally involve passive coating of Ti/TiO2 substrates with protein-resistant materials, and poly(ethylene glycol) (PEG) has proven advantageous for bestowing a nonbiofouling property on the surface of Ti/TiO2. However, the wider applications of Ti/TiO2-based materials to biomedical areas will require the introduction of biologically active moieties onto Ti/TiO2, in addition to nonbiofouling property. In this work, we therefore utilized surface-initiated polymerization to coat the Ti/TiO2 substrates with polymers presenting the nonbiofouling PEG moiety and subsequently conjugated biologically active compounds to the PEG-presenting, polymeric films. Specifically, a Ti/TiO2 surface was chemically modified to present an initiator for atom transfer radical polymerization, and poly(ethylene glycol) methacrylate (PEGMA) was polymerized from the surface. After activation of hydroxyl groups of poly(PEGMA) (pPEGMA) withN,N′-disuccinimidyl carbonate, biotin, a model compound, was conjugated to the pPEGMA films. The reactions were confirmed by infrared spectroscopy, X-ray photoelectron spectroscopy, contact angle goniometry, and ellipsometry. The biospecific binding of target proteins was also utilized to generate micropatterns of proteins on the Ti/TiO2 surface.
- Published
- 2009
42. Colorimetric Analysis on Flocculation of Bioinspired Au Self-Assembly for Biophotonic Application
- Author
-
Wan Soo Yun, Jasmine Austin, Shanghee Kim, Ansoon Kim, Jaetae Seo, Gun Yong Sung, Chil Seong Ah, and Wan-Joong Kim
- Subjects
Materials science ,Article Subject ,Absorption spectroscopy ,Surface plasmon ,Physics::Optics ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Colloidal gold ,lcsh:Technology (General) ,lcsh:T1-995 ,General Materials Science ,Self-assembly ,0210 nano-technology ,Absorption (electromagnetic radiation) ,Colorimetric analysis ,Plasmon ,Localized surface plasmon - Abstract
Gold nanoparticles exhibited strong surface plasmon absorption and couplings between neighboring particles within bioactivated self-assembly modified their optical properties. Colorimetric analysis on the optical modification of surface plasmon resoanance (SPR) shift and flocculation parameter functionalized bioinspired gold assembly for biophotonic application. The physical origin of bioinspired gold aggregation-induced shifting, decreasing, or broadening of the plasmon absorption spectra could be explained in terms of dynamic depolarization, collisional damping, and shadowing effects.
- Published
- 2009
43. Effect of aspect ratio of nanostrip on transformation of transverse domain wall due to adiabatic spin torque
- Author
-
Wan-Joong Kim, Kyung Jin Lee, Taeyeop Lee, and Soo-Man Seo
- Subjects
Physics::Fluid Dynamics ,Physics ,Transverse plane ,Domain wall (magnetism) ,Transformation (function) ,Aspect ratio ,Condensed matter physics ,Dynamics (mechanics) ,Torque ,Condensed Matter Physics ,Adiabatic process ,Electronic, Optical and Magnetic Materials ,Spin-½ - Abstract
We have studied the current-induced dynamics of the transverse domain wall in the adiabatic limit. Above the threshold current density for the continuous domain wall motion, the transverse wall is transformed by the injection of the antivortex. In general, the wall velocity increases and the wall width decreases as the antivortex is injected. However, detailed time-dependent profiles of the wall velocity and the wall width are significantly affected by the aspect ratio of the nanostrip. The mean velocity of the TW decreases as the aspect ratio increases.
- Published
- 2007
44. Domain wall pinning by alternating materials in current-induced domain wall motion
- Author
-
Taeyeop Lee, Wan-Joong Kim, and Kyung Jin Lee
- Subjects
Physics ,Condensed matter physics ,Edge (geometry) ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Physics::Fluid Dynamics ,Domain wall (magnetism) ,Position (vector) ,Condensed Matter::Superconductivity ,Current (fluid) ,Electric current ,Anisotropy ,Micromagnetics ,Current density - Abstract
For the application of current-induced domain wall motion, the pinning position of a domain wall must be precisely defined with a low depinning current density. A conventional way of pinning a domain wall is to use a notch which is patterned on an edge of nanostrip. As an alternative scheme of domain wall pinning, we performed micromagnetic investigation of the current-induced domain wall motion in a nanostrip with alternating materials. A segment with different magnetic parameters such as saturation magnetization, exchange constant or crystalline anisotropy can effectively pin a domain wall. It is because the segment acts as an energy barrier in the domain wall motion. Threshold current densities to depin the domain wall in nanostrips with alternating materials were of the order of 10 8 A/cm 2 , and can be modulated by changing the material parameters and the length of the segment.
- Published
- 2007
45. Surface-Initiated, Atom Transfer Radical Polymerization of Oligo(ethylene glycol) Methyl Ether Methacrylate and Subsequent Click Chemistry for Bioconjugation
- Author
-
Jeewon Lee, Bong-Soo Lee, Wan Joong Kim, Young Hwan Jung, Jungkyu K. Lee, Insung S. Choi, and Sang Jun Sim
- Subjects
Bioconjugation ,Free Radicals ,Polymers and Plastics ,Polymers ,Surface Properties ,Chemistry ,Atom-transfer radical-polymerization ,Biotin ,Proteins ,Biocompatible Materials ,Tissue Adhesions ,Bioengineering ,Ether ,Methacrylate ,Biomaterials ,chemistry.chemical_compound ,End-group ,Polymethacrylic Acids ,1,3-Dipolar cycloaddition ,Polymer chemistry ,Materials Chemistry ,Click chemistry ,Adsorption ,Ethylene glycol - Published
- 2007
46. Synthesis of New Anthracycline Derivatives Containing Lactic or Stearic Acid Moiety
- Author
-
Wan-Joong Kim, Young S. Rho, and Dong Jin Yoo
- Subjects
Anthracycline ,food and beverages ,General Chemistry ,Lactic acid ,chemistry.chemical_compound ,chemistry ,Nucleophile ,Reagent ,medicine ,Sodium lactate ,Moiety ,Organic chemistry ,Doxorubicin ,Stearic acid ,medicine.drug - Abstract
Novel anthracycline analogues 2-9 as potential anticancer agents were synthesized from daunomycin (1a) and doxorubicin (1b). Compounds 2, 6, and 7 were prepared by the nucleophilic displacement type esterification of a 14-bromodaunomycin (1c) with a sodium lactate, and stearic acid, respectively. Compounds 3-5 and 7-9 were prepared by the reaction of either daunomycin (1a) or doxorubicin (1b) with L-lactic and stearic acids in the presence of EDCI/PP reagents.
- Published
- 2006
47. Temperature-induced control of aspect ratio of gold nanorods
- Author
-
Chil Seong Ah, Kwang-Pil Lee, Hyung Ju Park, Wan Soo Yun, Wan-Joong Kim, and Insung S. Choi
- Subjects
Materials science ,Aqueous solution ,Hydrogen ,Aspect ratio ,Inorganic chemistry ,Nanowire ,food and beverages ,chemistry.chemical_element ,Nanoparticle ,Surfaces and Interfaces ,Condensed Matter Physics ,Ascorbic acid ,Silver nanoparticle ,Surfaces, Coatings and Films ,chemistry ,Nanorod - Abstract
Aspect ratio of gold nanorods can be controlled by simply adjusting the reaction temperature in the seed-mediated synthesis of the nanorods. The gold nanorods were synthesized by the injection of gold nanoparticle seeds of around 4nm in diameter into a reaction mixture containing hydrogen tetrachloroaurate, hexadecyltrimethylammonium bromide, and ascorbic acid. Average aspect ratio of the resulting nanorod increases from 1 to about 40 with decreasing the reaction temperature from 315to276K, which can be attributed to the temperature-induced change in the shape of the micellar templates. For further understanding of the growth mechanism, silver nanoparticles were also used as seeds in the preparation of the gold nanorod.
- Published
- 2006
48. Formation of Thermoresponsive Gold Nanoparticle/PNIPAAm Hybrids by Surface-Initiated, Atom Transfer Radical Polymerization in Aqueous Media
- Author
-
Wan-Joong Kim, Hyeon Choi, Hyun-jong Paik, Bokyung Kong, Dong Jin Kim, Insung S. Choi, and Sung Min Kang
- Subjects
Materials science ,Polymers and Plastics ,Atom-transfer radical-polymerization ,Organic Chemistry ,Nanoparticle ,Condensed Matter Physics ,Ring-opening polymerization ,Silver nanoparticle ,chemistry.chemical_compound ,Monomer ,chemistry ,Polymerization ,Dynamic light scattering ,Polymer chemistry ,Materials Chemistry ,Reversible addition−fragmentation chain-transfer polymerization ,Physical and Theoretical Chemistry - Abstract
We investigated the formation of thermoresponsive gold nanoparticle/poly(N-isopropylacrylamde) (AuNP/ PNIPAAm) core/shell hybrid structures by surface-initiated, atom transfer radical polymerization (SI-ATRP) in aqueous media and the effect of cross-linking on the thermoresponsiveness of the AuNP/PNIPAAm hybrids. The disulfide containing an ATRP initiator was attached onto AuNPs and the monomer, NIPAAm, was polymerized from the surface of AuNPs in the absence or presence of a cross-linker, ethylene diacrylate, in aqueous media at room temperature. The resulting brush-type and cross-linked AuNP/PNIPAAm hybrids were characterized by Fourier-transform infrared spectroscopy, transmission electron microscopy, and variable temperature dynamic light scattering.
- Published
- 2005
49. Size-Controlled Synthesis of Machinable Single Crystalline Gold Nanoplates
- Author
-
Chil Seong Ah, Wan Soo Yun, Hyung Ju Park, Yong Ju Yun, Wan-Joong Kim, and and Dong Han Ha
- Subjects
Materials science ,Hydrogen ,General Chemical Engineering ,Surface plasmon ,technology, industry, and agriculture ,chemistry.chemical_element ,Nanotechnology ,General Chemistry ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Molar ratio ,Sodium citrate ,Materials Chemistry ,Absorption (chemistry) - Abstract
Monodispersive size-controlled gold nanoplates were synthesized with high purity from the reduction of hydrogen tetrachloroaurate by reduced amount of sodium citrate, which kinetically controls the reaction pathway, in the presence of poly(vinyl pyrrolidone) (PVP). With the insufficient addition of the reductant, the molar ratio of sodium citrate and PVP relative to hydrogen tetrachloroaurate played an important role in determining the geometric shape and size of the product. These nanoplates were single crystals with planar width of 80−500 nm and thickness of 10−40 nm, exhibiting strong surface plasmon absorption in the near-infrared (NIR) region of 700−2000 nm. The gold nanoplates were used as the synthetically provided nanoblocks to fabricate single-crystalline nanocomponents, such as a nanoscaled gear or a nanoscaled letter.
- Published
- 2005
50. Functionalization of Shortened Single-Walled Carbon Nanotubes with Poly(p-dioxanone) by'Grafting-From' Approach
- Author
-
Kuk Ro Yoon, Insung S. Choi, and Wan-Joong Kim
- Subjects
chemistry.chemical_classification ,Thermogravimetric analysis ,Nanocomposite ,Materials science ,Polymers and Plastics ,Organic Chemistry ,Polymer ,Carbon nanotube ,Condensed Matter Physics ,Ring-opening polymerization ,law.invention ,Differential scanning calorimetry ,Polymerization ,chemistry ,law ,Polymer chemistry ,Materials Chemistry ,Thermal stability ,Physical and Theoretical Chemistry - Abstract
It has been a real challenge to form carbon nanotube (CNT)/polymer composites where CNTs are well-dispersed in the polymer matrix and the interactions between CNTs and polymers are effectively strong. In this paper, we applied surface-initiated, ring-opening polymerization (SI-ROP) of p-dioxanone (PDX) to shortened single-walled carbon naotubes (s-SWCNTs) and successfully formed s-SWCNT/PPDX composites (see Figure). Due to intimate interactions between s-SWCNTs and PPDX, we observed dramatic changes in PPDX properties upon the formation of the composites: 10%-weight-loss-temperature of PPDX increased by 20°C (measured by thermogravimetric analysis) and the patterns of T g and T m were greatly altered. We did not observed any noticeable peaks from the composite up to 120°C in differential scanning calorimetry (DSC), while DSC data of PPDX itself showed T g and T m at 13.4 and 103°C respectively.
- Published
- 2004
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.