Junhong Min

Chung-Ang University, Sŏul, Seoul, South Korea

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Publications (107)372.86 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: A cytochrome c/11-MUA heterolayer was fabricated to analyze its electrochemical characteristics in harsh conditions for a stable bioelectronic device. Since a cytochrome c/11-MUA heterolayer has been applied to construct the bioelectronics device such as non-volatile biomemory device, an understanding of electrochemical property of the heterolayer in harsh conditions such as variation of temperature and pH, and repetition of usage is necessary to manufacture a stable platform of bioelectronic device. Cytochrome c, a metalloprotein to have a heme group, was self-assembled on the Au surface via the chemical linker 11-mercaptoundecanoic acid (11-MUA). Immobilization of the heterolayer was confirmed by surface-enhanced Raman spectroscopy (SERS) and scanning tunneling microscopy (STM). The fatigue test was done by investigating the redox properties based on cyclic voltammetry (CV) of the heterolayer. The retention time test and pH dependence, thermal test of the fabricated heterolayer were conducted by CV, which showed that the fabricated film retained redox properties for more than 33 days, and from pH 5.0 to pH 9.0, from 15 °C to 55 °C. Taken together, our results show that a cytochrome c/11-MUA heterolayer is very stable, which could be used as a platform of bioelectronic device.
    Journal of Nanoscience and Nanotechnology 08/2015; 15(8). DOI:10.1166/jnn.2015.10445 · 1.34 Impact Factor
  • Yong Hyun Choi, Junhong Min, Sungbo Cho
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    ABSTRACT: Analysis on the interaction between proteins and cells is required for understanding the cellular behaviour and response. In this article, we characterized the adhesion and growth of 293/GFP cells on fetal bovine serum (FBS) coated indium tin oxide (ITO) electrode. Using optical and electrochemical measurement, it was able to detect the adsorption of the protein on the surface of the ITO electrode dependent on the concentration of the protein in the immersing solution or the immersing time. An increase in the amount of the adsorbed serum protein resulted in a decrease in anodic peak current and an increase in the charge transfer resistance extracted from the equivalent circuit fitting analysis. More cells adhered and proliferated on the ITO electrode which was pre-immersed in FBS medium rather than bare electrode. The effect of the FBS on cell behaviors was reflected in the impedance monitoring of cells at 21.5 kHz.
    Japanese Journal of Applied Physics 06/2015; 54(6S1):06FN03. DOI:10.7567/JJAP.54.06FN03 · 1.06 Impact Factor
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    ABSTRACT: The removal of humic acid from soil samples is of great importance for the nucleic acid based detection of pathogenic bacteria because it is one of the main enzyme (polymerase) reaction inhibitors. A simple and effective detection tool that detects pathogens in fertilized soil samples was developed here by the combination of sample preparation steps (the concentration of bacteria and removal of humic acid) and micro amplification steps in a microfluidic pillar chip with a single chamber. The pH dependent ternary interactions between E. coli O157:H7, humic acid, and solid surface were investigated and optimized for maximum adsorption of E. coli O157:H7 and desorption of humic acid on a solid surface to perform serial processes ((1) concentration of bacteria, (2) removal of humic acid, (3) nucleic acid extraction/amplification, and (4) fluorescent detection) in a microfluidic chip. These serial processes were successfully performed in a microfluidic PDMS chip with 400 micro pillars, resulting in the 87.5% rate of success in detection of 103 cfu of E. coli O157:H7 in fertilized soil (15 g) containing humic acid (up to 5000 ppm) for 2 h.
    Sensors and Actuators B Chemical 03/2015; 208. DOI:10.1016/j.snb.2014.11.028 · 3.84 Impact Factor
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    ABSTRACT: This study described a novel fabrication of fluorescence co-encapsulating silica nanotubes (F@SNT) and the further application of the as-synthesized nanostructure as a ratiometric pH sensor in buffer solution. Silica nanotubes (SNTs) embedded anodic alumina oxide (AAO) template was fabricated by sol–gel technique, tetramethyl rhodamine (TMR—the reference dye) was incorporated directly onto silica layer via hydrophobic interaction. Subsequently, fluorescent isothiocyanate (FITC-pH sensitive dye) was encapsulated inside poly-dimethylsiloxane (PDMS) matrix and the FITC-PDMS nanocomposite was doped into the hollow structure of SNT using nano-molding lithography. On removing AAO, free-standing SNTs were obtained and were subsequently applied as a ratiometric pH sensor in phosphate buffer solution. The dual dye-doped SNTs showed excellent fluorescence and a good pH sensing performance from pH 5.2–8.0. The results were distinguishable by the emission spectra and by fluorescent visualization. High photostability, sensitivity, biocompatibility with adjustable sizes make dual dye doped-SNT a promising nanostructure for bioapplications.
    Journal of Nanoscience and Nanotechnology 11/2014; 14(11). DOI:10.1166/jnn.2014.9974 · 1.34 Impact Factor
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    ABSTRACT: For early diagnosis of several diseases, highly sensitive detection technology is necessary to analyze biomarkers quantitatively at low concentrations. To develop a sensitive detection system, a well-designed probe is very critical, and it mainly consisted of several bio- and nanomaterials, such as gold (Au) and silica nanoparticles. In this study, an ultrasensitive nanoprobe for the detection of versatile biomolecules was developed by the sandwich immuno-reaction technique. The developed nanoprobe was composed of aptamer-functionalized Au nanoparticles and magnetic microparticles (MMPs). In order to enhance the detection ability of the Au probe, the orientation of antibodies was defined using aptamer-induced specific binding to the F c region of the antibody. And target antigens could be detected by the real-time polymerase chain reaction (RT-PCR) method, which was able to measure the concentration of aptamers with Au nanoparticles. Selected targets were prostate specific antigen (PSA) and Escherichia coli O157:H7 (E. coli O157:H7). This system can be applied to the diagnosis of several diseases and environmental toxicity testing, especially for the detection of very low concentrations.
    Science of Advanced Materials 11/2014; 6(11). DOI:10.1166/sam.2014.2239 · 2.91 Impact Factor
  • Applied Surface Science 11/2014; 320:448-454. DOI:10.1016/j.apsusc.2014.09.020 · 2.54 Impact Factor
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    ABSTRACT: A simple and sensitive amperometric sensor was developed based on electrochemical co-reduction of graphene oxide/nanoparticle (ERGO-NP) composite films by chronoamperometrymethod on indium tin oxide (ITO) electrodes. By analyzing the properties of the composite films with experimental results and theoretical investigations, a comprehensive report on the physical and electrochemical interfacial properties of graphene mixed gold nanoparticles composite electrode is presented. The developed electrodes were applied for the detection of hydrogen peroxide (H2O2) based on the direct electrochemistry of horseradish peroxidase (HRP). Standard carbodiimide chemistry enabled the covalent tethering of HRP on to the modified film thus maintaining its native structures, consequently facilitating the direct electron transfer between the protein and the underlying surface. The electrochemical result revealed that the ERGO-NP/ITO electrodes exhibited much higher conductivity (ca. 5 times) when compared with unmodified electrode. The developed sensor using amperometric measurements revealed high sensitivity (1808.9 mu A.mM(-1) cm(-2)), with detection limit (0.6 mu M) achieved under optimized conditions toward H2O2. Further, the sensor showed good specificity, stability and reproducibility toward H2O2 detection, therefore results proved that well-dispersed, high surface area and highly conductive modified surface could be a promising material for protein adsorption and fabrication of electrochemical biosensors.
    Journal of The Electrochemical Society 10/2014; 161(14):G133-G140. DOI:10.1149/2.1001414jes · 2.86 Impact Factor
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    ABSTRACT: Sample preparation has recently been an issue in the detection of food poisoning pathogens, particularly viruses such as norovirus (NoV), in food because of the complexity of foods and raw fresh materials. Here, we demonstrate a total analytical microfluidic chip module to automatically perform a series of essential processes (cell concentration, lysis (RNA extraction), nucleic acid amplification, and detection) for the fast but sensitive detection of norovirus in oysters. The murine NoV spiked oyster was stomached using a standard method. The supernatant was first loaded into a shape switchable sample preparation chamber consisting of charge switchable micro-beads. Murine NoV, which was adsorbed on microbeads by electrostatic physisorption, was lysed using bead beating. The extracted RNA was transferred to the detection chamber to be amplified using Nucleic Acid Sequence Based Amplification (NASBA). The optimal surface functionality, size, and number of microbeads were achieved for the virus concentration and the stable RNA extraction in the shape-switchable micro-channel. As a result, murine NoV in a single oyster was successfully detected within 4h by the microfluidic chip developed here, and could be directly applied to the large volume environmental sample as well as the food sample. Copyright © 2014 Elsevier B.V. All rights reserved.
    Biosensors & Bioelectronics 10/2014; 67. DOI:10.1016/j.bios.2014.09.083 · 6.45 Impact Factor
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    ABSTRACT: A novel incentive enzymatic glucose detection using ratiometric fluorescent co-doped silica nanotube was devel-oped. With the great biocompatibility and multifunctional structure, silica nanotube allows both co-encapsulation of fluorescent dyes and bioconjugation of glucose oxidase without increasing its dynamic size. In our study, two kinds of fluorophore, namely Fluorescent isothiocyanate and Tetramethyl rhodamine, were employed as reporting and calibrating probe, respectively. Firstly, silica nanotubes were synthesized using anodic alumina membrane and Tetramethyl rhodamine, pH-insensitive dye, was embedded inside silica matrix during synthe-sis. Secondly, Fluorescent isothiocyanate, pH-sensitive dye, was subsequently embedded inside hollow void of nanotube using nano-molding lithography. Finally, glucose oxidase was covalently immobilized onto the outer surface of free-standing silica nanotubes. During enzymatic reaction, gluconic acid was generated and decreased pH of solution. The concentration of glucose was quantified by fluorescent ratiometric measurement based on the decreased emission intensity of Fluoresecein thioisocyanate compared to that of Tetramethyl rhodamine
    Science of Advanced Materials 10/2014; 6. DOI:10.1166/sam.2014.2211 · 2.91 Impact Factor
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    ABSTRACT: This study described the prospect of silica nanotube surface modification in simultaneous detection of pathogenic bacteria by coupling cation exchange magnetic separation with quantum dot label-ing. The outer surface of magnetic nanoparticles embedded long silica nanotube (capturing SNT) was modified with poly-L-lysine to serve as a cation exchange magnetic nano-complex to capture and isolateEscherichia coli (E.coli)O157:H7 andSalmonella enteritis typhimurium(S.typhimurium) in aqueous phase. Antibody conjugated quantum dot-embedded short SNT (reporting SNT) was used to simultaneously detect both bacteria, giving a high intensity and photo-stable fluorescent image that can detect single leveled bacterium binding on the capturing SNT. The fluorescent inten-sity generated from the capturing of both bacteria at different concentration was in the range of 10^2 –10^5 CFU/ml for bothE.coli and S.typhimurium. Keywords:Silica Nanotube, Quantum Dot, Cation Exchange, Bacteria Concentration
    Journal of Nanoscience and Nanotechnology 08/2014; 14(8):5646-5649. DOI:10.1166/jnn.2014.8784 · 1.34 Impact Factor
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    ABSTRACT: Recently, the fabrication of protein bilayer has been required for the development of protein or enzyme complex formation. In the present study, we fabricated a fusion protein bilayer composed of recombinant azurin-cytochrome P450, which was synthesized by a site-specific sortase-mediated ligation method. The Pseudomonas aeruginosa azurin was modified by DNA recombinant technique, for enzymatic ligation and immobilization. The Pseudomonas putida cytochrome P450 was also modified for enzymatic ligation. The recombinant metalloproteins were conjugated via the sortase A. The conjugation was confirmed by SDS-PAGE and UV-vis. Then, the prepared fusion protein was immobilized on Au substrate, by the self-assembly method. The Azu-P450 (recombinant azurin-cytochrome P450) fusion protein layer was confirmed by AFM (Atomic Force Microscopy) and SERS (Surface-enhanced Raman Spectroscopy), to confirm the fusion protein bilayer orientation. Moreover, the electrochemical property of Azu-P450 was observed by cyclic voltammetry (CV). As a result, the Azu-P450 fusion protein bilayer shows good orientation on the Au substrate. Also, the original redox property of this fusion protein bilayer has been well maintained. The proposed fusion protein bilayer can.
    Colloids and surfaces B: Biointerfaces 08/2014; 120. DOI:10.1016/j.colsurfb.2014.03.034 · 4.29 Impact Factor
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    ABSTRACT: Several fluorescent or luminescent organisms with biological, chemical, and ecological diversity have been proposed as substitutes for use in new imaging and diagnostic technologies. Inspired by these trends, we designed a synthetic fluorescent light-encoding particulate to serve as a novel and prospective cancer-diagnostic imaging platform. The fluorescence-emitting particulate was used practically for both in vitro and in vivo selective cancer diagnostic imaging. (c) 2014 Elsevier B.V. All rights reserved.
    Colloids and surfaces B: Biointerfaces 07/2014; 122. DOI:10.1016/j.colsurfb.2014.07.033 · 4.29 Impact Factor
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    ABSTRACT: This study describes a simple but effective combinatory effect of magnetic silica nanotubes (MSNTs) in bacterial separation and impedimetric signal enhancement for the label-free detection of Salmonella typhimurium. The outer surface of MSNTs was functionalized with positive charges for the successful concentration and the isolation of bacteria from a high-volume sample. Scanning electron microscopy (SEM) was used to confirm the bacterial adsorption on MSNT. Antibody specific to S. typhimurium was immobilized on the interdigitated microelectrode of an impedimetric sensor. Bacteria binding MSNT (bacteria–MSNT complex) was successfully conjugated with antibody immobilized impedimetric sensor. The decrease of the impedance response was automatically shown due to the antigen–antibody recognition between bacteria and antibody immobilized impedimetric microelectrodes. The presence of MSNT significantly enhanced the impedimetric sensor performance by generating highly discriminated impedance signals in correspond with different bacterial concentrations 103–107 CFU. The total detection time from bacteria isolation to measurement was completed within roughly 30 min with low cost and an ease of operation. This study shows the potential use of MSNT in antibody-free bio-separation and in impedimetric signal enhancement with the effort to develop a label-free, automatic pathogenic detection system.
    Sensors and Actuators B Chemical 07/2014; 197:314–320. DOI:10.1016/j.snb.2014.02.089 · 3.84 Impact Factor
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    ABSTRACT: The films organized with biomolecules and organic materials are important elements for developing bioelectronic devices according to their electron transfer property. Until now, several concepts of techniques have been accomplished to be used for developing biomemory devices. However it is difficult to detect the current signal from the electron transfer between biomolecules and the substrate in these fabricated films. To enhance the current signal, the silver nanoparticle was introduced to the cytochrome c in this present study. The surface morphology of the fabricated film was investigated by atomic force microscopy. The current signal enhancement was investigated by cyclic voltammetry. As a result, we could obtain the redox potentials. Moreover, by chronoamperometry, we validated that this proposed layer showed the signal-enhanced memory property for biomemory devices. This new film composed of the cytochrome c and the silver nanoparticle showed the signal enhancement. Using chronoamperometry, the areas under the graphs between 0 s and 50 ms were calculated. The calculated result showed that the areas under the cytochrome c/SNP graph and cytochrome c graph were 6.93 x 10(-7) C and 4.54 x 10(-7) C, respectively. This numerical value verified that the cytochrome c/silver nanoparticle hetero-layer film showed better electron charged biomemory performance compared to the cytochrome c monolayer. This signal-enhanced film can be applied to the bioelectronic devices which are able to replace existing electronic devices in the near future.
    Journal of Nanoscience and Nanotechnology 03/2014; 14(3):2466-71. DOI:10.1166/jnn.2014.8542 · 1.34 Impact Factor
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    ABSTRACT: Major challenges in molecular electronics include miniaturization, and the realization of a simple function to alter silicon-based electronics. It has been hard to develop a single molecular-based computing system, since such systems need complex functionality to be developed at the single-molecular level. To develop a molecular-based biocomputing system, a bioprocessing device is demonstrated that consists of recombinant azurin/DNA/inorganic material hybrid to perform the various functions in a device. A metalloprotein which exhibits redox behavior is used as a biomemory source. The redox property could be controlled with command materials (conducting nanoparticles, heavy metal ions, and semiconducting nanoparticles) to perform ‘information reinforcement,’ ‘information regulation,’ and ‘information amplification’ functions, respectively. This bioprocessing device could be a foundation to develop single-biomolecular-based computing systems.
    Advanced Functional Materials 03/2014; 24(12). DOI:10.1002/adfm.201302397 · 10.44 Impact Factor
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    ABSTRACT: A subnanometer gap-separated linear chain gold nanoparticle (AuNP) silica nanotube peapod (SNTP) was fabricated by self-assembly. The geometrical configurations of the AuNPs inside the SNTPs were managed in order to pose either a single-line or a double-line nanostructure by controlling the diameters of the AuNPs and the orifice in the silica nanotubes (SNTs). The AuNPs were internalized and self-assembled linearly inside the SNTs by capillary force using a repeated wet-dry process on a rocking plate. Transmission electron microscopy (TEM) images clearly indicated that numerous nanogap junctions with sub-1-nm distances were formed among AuNPs inside SNTs. Finite-dimension time domain (FDTD) calculations were performed to estimate the electric field enhancements. Polarization-dependent SERS spectra of bifunctional aromatic linker p-mercaptobenzoic acid (p-MBA)-coated AuNP-embedded SNTs supported the linearly aligned nanogaps. We could demonstrate a silica wall-protected nanopeapod sensor with single nanotube sensitivity. SNTPs have potential application to intracellular pH sensors after endocytosis in mammalian cells for practical purposes. The TEM images indicated that the nanogaps were preserved inside the cellular constituents. SNTPs exhibited superior quality surface-enhanced Raman scattering (SERS) spectra in vivo due to well-sustained nanogap junctions inside the SNTs, when compared to simply using AuNPs without any silica encapsulation. By using these SNTPs, a robust intracellular optical pH sensor could be developed with the advantage of the sustained nanogaps, due to silica wall-protection.
    Journal of the American Chemical Society 02/2014; 136(10). DOI:10.1021/ja411034q · 11.44 Impact Factor
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    ABSTRACT: In the present study, we investigated the simultaneous detection of multilevel electrochemical signals from various metalloprotein heterolayers for the bioelectronic devices. A layer-by-layer assembly method based on simple electrostatic interaction was introduced to form protein bilayers. The gold substrate was modified with poly (ethylene glycol) thiol acid as the precursor, which introduced negative charges to the surface. Based on the isoelectric point, net-charge controlled metalloproteins by pH adjustment were sequentially immobilized on this negatively charged substrate. The degree of protein immobilization on the gold substrate was confirmed by surface plasmon resonance spectroscopy, and the surface topology changes due to the protein immobilization were confirmed by atomic force microscopy. Redox signals in the protein layers were measured by cyclic voltammetry. As a result, various redox signals generated from different metalloproteins on a single electrode were monitored. This proposed method for the detection of multi-level electrochemical signals can be directly applied to bioelectronic devices that store multi-information in a single electrode.
    Thin Solid Films 01/2014; 551:174–180. DOI:10.1016/j.tsf.2013.11.077 · 1.87 Impact Factor
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    ABSTRACT: Rare-earth doped nanoparticle (RE), termed upconversion nanoparticle (UCNP), is a new generation of phosphorescence which has recently attracted significant research interest. Due to the unique upconversion properties, UCNP has been considered to be an excellent alternative for conventional fluorescence. Since its first emergence in mid-1960s, UCNPs have been studied in a wide range of fields, including those in biological applications. Owing to its suitable size distribution and biocompatibility, UCNP could be conjugated with various kinds of biomolecules, resulting in the development of numerous biological platforms such as biodetection assays and therapeutic modalities. The unique optical properties of UCNP such as prominent luminescence, deep penetration to biological tissues without damaging the cells, low background and high resistance to photo-bleaching enhance UCNP prospects as an excellent contrast agent in both in vitro and in vivo. In this review, we discuss the recent developments of UCNP in bioassays, optical imaging, and therapy, also the prospects and challenges of UCNP-based detection in the development of biomedical science.
    Journal of Nanoscience and Nanotechnology 01/2014; 14(1):157-74. DOI:10.1166/jnn.2014.8894 · 1.34 Impact Factor
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    ABSTRACT: Biomolecular computing devices that are based on the properties of biomolecular activities offer a unique possibility for constructing new computing structures. A new concept of using various biomolecules has been proposed in order to develop a protein-based memory device that is capable of switching physical properties when electrical input signals are applied to perform memory switching. To clarify the proposed concept, redox protein is immobilized on Au nanoelectrodes to catalyze reversible reactions of redox-active molecules, which is controlled electrochemically and reversibly converted between its ON/OFF states. In this review, we summarize recent research towards developing nanoscale biomemory devices including design, synthesis, fabrication, and functionalization based on the proposed concept. At first we analyze the memory function properties of the proposed device at bulk material level and then explain the WORM (write-once-read-many times) nature of the device, later we extend the analysis to multi-bit and multi-level storage functions, and then we focus the developments in nanoscale biomemory devices based on the electron transport of redox molecules to the underlying Au patterned surface. The developed device operates at very low voltages and has good stability and excellent reversibility, proving to be a promising platform for future memory devices.
    Journal of Nanoscience and Nanotechnology 01/2014; 14(1):433-46. DOI:10.1166/jnn.2014.9006 · 1.34 Impact Factor
  • Jaehwan Ahn, Sungbo Cho, Junhong Min
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    ABSTRACT: Electrochemical measurements using the microelectrodes are increasingly utilized for the label-free detection of the small amount of biological materials such as DNA, protein, and cells. However, the interfacial electrode impedance increases and may hinder the detection of weak signals as the size of electrode decreases. To enhance the measurement sensitivity while reducing the electrode size, in this study, microelectrodes employing a nanoporous structure were fabricated and characterized by using electrical impedance spectroscopy. We made the highly ordered honeycomb nanoporous structure of Anodic Aluminum Oxide (AAO) by electrochemical anodizing and formed Au layer on the surface of AAO (Au/AAO) by electroless Au plating method. The electrical characteristics of the fabricated Au/AAO electrodes were evaluated by using de Levie's model derived for the pore electrodes. As a result, the interfacial electrode impedance of the fabricated Au/AAO electrodes was 2-3 order lower than the value of the planar electrodes at frequencies below 1 kHz. It implies this nanoporous electrode could be directly applied to label free detection of biomaterials.
    Journal of Nanoscience and Nanotechnology 11/2013; 13(11):7482-6. DOI:10.1166/jnn.2013.7904 · 1.34 Impact Factor

Publication Stats

640 Citations
372.86 Total Impact Points

Institutions

  • 2012–2015
    • Chung-Ang University
      • School of Integrative Engineering
      Sŏul, Seoul, South Korea
  • 2007–2011
    • Gachon University
      • College of BioNano Technology
      Sŏngnam, Gyeonggi Province, South Korea
  • 1997–2010
    • Sogang University
      • Department of Chemical and Biomolecular Engineering
      Seoul, Seoul, South Korea
  • 2000
    • Korea University
      Sŏul, Seoul, South Korea