Publications by authors named "Doohwan Jung"

12 Publications

  • Page 1 of 1

A CMOS Multi-Modal Electrochemical and Impedance Cellular Sensing Array for Massively Paralleled Exoelectrogen Screening.

IEEE Trans Biomed Circuits Syst 2021 04 25;15(2):221-234. Epub 2021 May 25.

The paper presents a 256-pixel CMOS sensor array with in-pixel dual electrochemical and impedance detection modalities for rapid, multi-dimensional characterization of exoelectrogens. The CMOS IC has 16 parallel readout channels, allowing it to perform multiple measurements with a high throughput and enable the chip to handle different samples simultaneously. The chip contains a total of 2 × 256 working electrodes of size 44 μm × 52 μm, along with 16 reference electrodes of dimensions 56 μm × 399 μm and 32 counter electrodes of dimensions 399 μm × 106 μm, which together facilitate the high resolution screening of the test samples. The chip was fabricated in a standard 130nm BiCMOS process. The on-chip electrodes are subjected to additional fabrication processes, including a critical Al-etch step that ensures the excellent biocompatibility and long-term reliability of the CMOS sensor array in bio-environment. The electrochemical sensing modality is verified by detecting the electroactive analyte NaFeEDTA and the exoelectrogenic Shewanella oneidensis MR-1 bacteria, illustrating the chip's ability to quantify the generated electrochemical current and distinguish between different analyte concentrations. The impedance measurements with the HEK-293 cancer cells cultured on-chip successfully capture the cell-to-surface adhesion information between the electrodes and the cancer cells. The reported CMOS sensor array outperforms the conventional discrete setups for exoelectrogen characterization in terms of spatial resolution and speed, which demonstrates the chip's potential to radically accelerate synthetic biology engineering.
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http://dx.doi.org/10.1109/TBCAS.2021.3068710DOI Listing
April 2021

Sulfonate Version of OHPAS Linker Has Two Distinct Pathways of Breakdown: Elimination Route Allows Para-Hydroxy-Protected Benzylsulfonate (PHP-BS) to Serve as an Alternative Self-Immolative Group.

Bioconjug Chem 2020 05 2;31(5):1392-1399. Epub 2020 Apr 2.

Recently we have reported that the ortho-hydroxy-protected aryl sulfate (OHPAS) system can be exploited as a new self-immolative group (SIG) for phenolic payloads. We extended the system to nonphenolic payloads by simply introducing a para-hydroxy benzyl (PHB) spacer. As an additional variation of the system, we explored a benzylsulfonate version of the OHPAS system and found that it has two distinct breakdown pathways, cyclization and 1,4-elimination, the latter of which implies that para-hydroxy-protected (PHP) benzylsulfonate (BS) can also be used as an alternative SIG. The PHP-BS system was found to be stable chemically and in mouse and human plasma, having payload release rates comparable to those of the original OHPAS conjugates.
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http://dx.doi.org/10.1021/acs.bioconjchem.0c00116DOI Listing
May 2020

Intracellular cardiomyocytes potential recording by planar electrode array and fibroblasts co-culturing on multi-modal CMOS chip.

Biosens Bioelectron 2019 Nov 28;144:111626. Epub 2019 Aug 28.

School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA, USA. Electronic address:

Intracellular action potential signals reveal enriched physiological information. Patch clamp techniques have been widely used to measure intracellular potential. Despite their high signal fidelity, they suffer from low throughput. Recently, 3D nanoelectrodes have been developed for intracellular potential recording. However, they are limited by scalability, yield, and cost, directly constraining their use in monitoring large number of cells and high throughput applications. In this paper, we demonstrate intracellular potential monitoring of cardiomyocytes using simple 2D planar electrode array in a standard CMOS process without patch clamps or post fabricated 3D nanoelectrodes. This is enabled by our unique cardiomyocytes/fibroblasts co-culturing technique and electroporation. The co-cultured fibroblasts promote tight sealing of cardiomyocytes on electrodes and enable high-fidelity intracellular potential monitoring based on 2D planar electrode. Compared to existing technologies, our platform has a unique potential to achieve an unprecedented combination of throughput, spatiotemporal resolution, and a tissue-level field-of-view for cellular electrophysiology monitoring.
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http://dx.doi.org/10.1016/j.bios.2019.111626DOI Listing
November 2019

Aryl Sulfate is a Useful Motif for Conjugating and Releasing Phenolic Molecules: Sulfur Fluorine Exchange Click Chemistry Enables Discovery of Ortho-Hydroxy-Protected Aryl Sulfate Linker.

Bioconjug Chem 2019 07 28;30(7):1957-1968. Epub 2019 Jun 28.

A new self-immolative linker motif, Ortho Hydroxy-Protected Aryl Sulfate (OHPAS), was devised, and OHPAS-containing antibody drug conjugates (ADC) were tested in vitro and in vivo. Conveniently synthesized using Sulfur Fluorine Exchange (SuFEx) chemistry, it is based structurally on diaryl sulfate, with one aryl acting as a payload and the other as a self-immolative sulfate unit having a latent phenol function at the ortho position. The chemically stable OHPAS linker was stable in plasma samples from 5 different species, yet it can release the payload molecule smoothly upon chemical or biological triggering. The payload release proceeds via intramolecular cyclization, producing a cyclic sulfate coproduct that eventually hydrolyzes to a catechol monosulfate. A set of OHPAS-containing ADCs based on Trastuzumab were prepared with a drug to antibody ratio of ∼2, and were shown to be cytotoxic in 5 different cancer cell lines in vitro and dose-dependently inhibited tumor growth in a NCI-N87 mouse xenograft model. We conclude that OHPAS conjugates will be of considerable use for delivering phenol-containing payloads to tissues targeted for medical intervention.
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http://dx.doi.org/10.1021/acs.bioconjchem.9b00340DOI Listing
July 2019

Introduction of Para-Hydroxy Benzyl Spacer Greatly Expands the Utility of Ortho-Hydroxy-Protected Aryl Sulfate System: Application to Nonphenolic Payloads.

Bioconjug Chem 2019 07 28;30(7):1969-1978. Epub 2019 Jun 28.

The ortho-hydroxy-protected aryl sulfate (OHPAS) linker is composed of a diaryl sulfate backbone equipped with a latent phenol moiety at the ortho position of one of the aryl units. The Ar-OH released when the ortho phenol undergoes intramolecular cyclization and displaces the second aryl unit can be viewed as a payload. We have shown in the preceding paper that the OHPAS linkers are highly stable chemically and in various plasmas, yet release payloads when exposed to suitable triggering conditions. As an extension of the OHPAS system, we employed a para-hydroxy benzyl (PHB) spacer for coupling to nonphenolic payloads; this tactic again provided a highly stable system capable of smooth release of appended payloads. The PHB modification works beautifully for tertiary amine and N-heterocycle payloads.
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http://dx.doi.org/10.1021/acs.bioconjchem.9b00341DOI Listing
July 2019

Electrode-Electrolyte Interface Impedance Characterization of Ultra-Miniaturized Microelectrode Arrays Over Materials and Geometries for Sub-Cellular and Cellular Sensing and Stimulation.

IEEE Trans Nanobioscience 2019 04 15;18(2):248-252. Epub 2019 Mar 15.

Electrochemical interfaces with low-impedance, high biocompatibility, and long-term stability are of paramount importance for microelectrode arrays (MEAs), that are widely used in numerous cellular sensing/stimulation applications, e.g., brain interface, electroceuticals, neuroprosthetics, drug discovery, chemical screening, and fundamental biological research. It is becoming increasingly critical since sensing/actuations at sub-cellular resolution necessitate ultra-miniaturized electrodes, which exhibit exacerbated electrochemical interfaces, especially on interfacial impedance. This paper reports the first comprehensive characterization and interfacial electrochemical impedance spectroscopy (EIS) of the ultra-miniaturized electrodes for different electrode sizes ( 8×8 μm , 16×16 μm , and 32×32 μm ) and a wide material collection (Au, Pt, TiN, and ITO). Equivalent electrochemical interfacial circuit models with interface capacitance, charge transfer resistance, and solution resistance are obtained for all the electrode designs based on their EIS measurements. The results can potentially guide the designs of ultra-miniaturized MEAs for future bioelectronics systems.
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http://dx.doi.org/10.1109/TNB.2019.2905509DOI Listing
April 2019

Preparation and Characteristics of SiO Coated Carbon Nanotubes with High Surface Area.

Nanomaterials (Basel) 2012 Jun 18;2(2):206-216. Epub 2012 Jun 18.

Fuel Cell Research Center, Korea Institute of Energy Research, Daejeon 305-343, Korea.

An easy method to synthesize SiO coated carbon nanotubes (SiO-CNT) through thermal decomposition of polycarbomethylsilane adsorbed on the surface of CNTs is reported. Physical properties of SiO-CNT samples depending on various Si contents and synthesis conditions are examined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen isotherm, scanning electron microscope (SEM), and transmission electron microscope (TEM). Morphology of the SiO-CNT appears to be perfectly identical to that of the pristine CNT. It is confirmed that SiO is formed in a thin layer of approximately 1 nm thickness over the surface of CNTs. The specific surface area is significantly increased by the coating, because thin layer of SiO is highly porous. The surface properties such as porosity and thickness of SiO layers are found to be controlled by SiO contents and heat treatment conditions. The preparation method in this study is to provide useful nano-hybrid composite materials with multi-functional surface properties.
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http://dx.doi.org/10.3390/nano2020206DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5327897PMC
June 2012

Electrochemical catalytic activity for oxygen reduction reaction of nitrogen-doped carbon nanofibers.

J Nanosci Nanotechnol 2011 Jul;11(7):6350-8

Advanced Energy Technology, University of Science and Technology (UST), Daejeon 305-333, Republic of Korea.

The electrocatalytic activity of nitrogen-doped carbon nanofibers (N-CNFs), which are synthesized directly from vaporized acetonitrile over nickel-iron based catalysts, for oxygen reduction reaction (ORR), was investigated. The nitrogen content and specific surface area of N-CNFs can be controlled through the synthesis temperature (300-680 degrees C). The graphitization degree of N-CNFs also are significantly affected by the temperature, whereas the chemical compositions of nitrogen species are similar irrespective of the synthesis conditions. From measurement of the electrochemical double layer capacitance, the surface of N-CNFs is found to have stronger interaction with ions than undoped-carbon surfaces. Although N-CNFs show higher over-potential than Pt catalysts do, N-CNFs were observed to have a noticeable ORR activity, as opposed to the carbon samples without nitrogen doping. The activity dependency of N-CNFs on the content of the nitrogen with which they were doped is discussed, based on the experiment results. The single cell of the direct methanol fuel cell (DMFC) was tested to investigate the performance of a membrane-electrode assembly that includes N-CNFs as the cathode catalyst layer.
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http://dx.doi.org/10.1166/jnn.2011.4443DOI Listing
July 2011

Study on the water flooding in the cathode of direct methanol fuel cells.

J Nanosci Nanotechnol 2011 Jul;11(7):5788-94

Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 305-701, Republic of Korea.

Water flooding phenomena in the cathode of direct methanol fuel cells were analyzed by using electrochemical impedance spectroscopy. Two kinds of commercial gas diffusion layers with different PTFE contents of 5 wt% (GDL A5) and 20 wt% (GDL B20) were used to investigate the water flooding under various operating conditions. Water flooding was divided into two types: catalyst flooding and backing flooding. The cathode impedance spectra of each gas diffusion layer was obtained and compared under the same conditions. The diameter of the capacitive semicircle became larger with increasing current density for both, and this increase was greater for GDL B20 than GDL A5. Catalyst flooding is dominant and backing flooding is negligible when the air flow rate is high and current density is low. An equivalent model was suggested and fitted to the experimental data. Parameters for catalyst flooding and backing flooding were individually obtained. The capacitance of the catalyst layer decreases as the air flow rate decreases when the catalyst flooding is dominant.
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http://dx.doi.org/10.1166/jnn.2011.4504DOI Listing
July 2011

Characteristics of porous carbon nano-fibers synthesized by selective catalytic gasification.

J Nanosci Nanotechnol 2011 Jul;11(7):5775-80

Advanced Energy Technology, University of Science and Technology (UST), 113 Gwahangno, Yuseong-gu, Daejeon, 305-333, Republic of Korea.

Carbon nanofibers (CNFs) with uniquely oriented channels were prepared via selective catalytic gasification in air at 450 and 500 degrees C, using Pt or Ru nano particles as catalysts. Catalytic gasification was chosen because it can selectively generate channels in the vicinity of the catalyst particles at relatively low temperatures, where thermal oxidation does not intensively occur. The structures and surface properties of the CNFs were examined via X-ray diffraction, analysis of the nitrogen adsorption-desorption isotherms, and high-resolution transmission electron microscopy. The effects of the catalyst species and loading amount on the formation of pores (channels) were investigated. The gasification mechanism, especially the channeling direction, throught the selection of the gasification catalysts, is discussed based on the results. This process can be effectively utilized for preparation of porous carbons, which have a well-aligned graphitic structure, and also channel-type pores can be designed by selection of gasification catalysts and conditions. The present porous CNF can be applied for catalyst support in fuel cells, without further treatment (e.g., acid treatment for the removal of metallic components).
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http://dx.doi.org/10.1166/jnn.2011.4452DOI Listing
July 2011

Preparation of mesoporous carbon-carbon nanotube composites using the template method.

J Nanosci Nanotechnol 2011 Jul;11(7):5761-8

Advanced Fuel Cell Research Center, Korea Institute of Energy Research, 102 Gajeong-ro, Yuseong-gu, Daejeon 305-343, Republic of Korea.

Reported herein is a simple template method for preparing mesoporous carbons (MPCs) from a mesophase pitch, using homemade nano-sized MgOs and MgO-carbon nanotube (CNT) composites as templates. Nano-sized MgO particles containing iron-molybdenum were synthesized through the heat treatment of the precursor ash, and the MgO-CNT composites were prepared via catalytic chemical vapor deposition of CH4 over the MgO-based particles. MPCs with a high surface area of 443-578 m2/g were obtained through the heat treatment of well-mixed mesophase pitch-MgO (or MgO-CNT), followed by mild-acid treatment to remove the MgO and other catalyst components. All the materials (the precursors, nano-particles, and MPCs) were analyzed via powder X-ray diffraction, N2 adsorption-desorption isotherms, scanning electron microscopy, and high resolution transmission electron microscopy. The formation of the pore structure in the MPCs is discussed, and the potential application of the MPC-CNT composite is demonstrated through cyclic voltammetry.
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http://dx.doi.org/10.1166/jnn.2011.4448DOI Listing
July 2011

Ionic-liquid-assisted sonochemical synthesis of carbon-nanotube-based nanohybrids: control in the structures and interfacial characteristics.

Small 2009 Aug;5(15):1754-60

Department of Chemsitry and Biomolecular Engineering (BK 21), Korea Advanced Institute of Science and Technology, Yuseong-gu, Daejeon, 305-701, Republic of Korea.

A versatile, facile, and rapid synthetic method of advanced carbon nanotube (CNT)-based nanohybrid fabrication, or the so-called ionic-liquid-assisted sonochemical method (ILASM), which combines the supramolecular chemistry between ionic liquids (ILs) and CNTs with sonochemistry for the control in the size and amount of uniformly decorated nanoparticles (NPs) and interfacial engineering, is reported. The excellence in electrocatalysis of hybrid materials with well-designed nanostructures and favorable interfaces is demonstrated by applying them to electrochemical catalysis. The synthetic method discussed in this report has an important and immediate impact not only on the design and synthesis of functional hybrid nanomaterials by supramolecular chemistry and sonochemistry but also on applications of the same into electrochemical devices such as sensors, fuel cells, solar cells, actuators, batteries, and capacitors.
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http://dx.doi.org/10.1002/smll.200900128DOI Listing
August 2009
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