Publications by authors named "Seunghun Hong"

132 Publications

Reusable surface plasmon resonance biosensor chip for the detection of H1N1 influenza virus.

Biosens Bioelectron 2020 Nov 25;168:112561. Epub 2020 Aug 25.

Department of Physics and Astronomy, And Institute of Applied Physics, Seoul National University, Seoul, 08826, Republic of Korea. Electronic address:

We developed a reusable magnetic surface plasmon resonance (SPR) sensor chip for detecting various target molecules repeatedly in a conventional SPR system. Here, ferromagnetic patterns on a SPR sensor chip were utilized to trap a layer of magnetic particles, and they were utilized as a solid substrate for SPR sensing in a conventional SPR system. After a sensing experiment, the used magnetic particles were removed by external magnetic fields, and a new layer of magnetic particles was immobilized to the SPR sensor chip for additional sensing measurements. Since magnetic particles were trapped on the ferromagnetic patterns, we could use our reusable SPR chip for SPR sensing measurements in a traditional SPR system without any applied magnetic fields. Significantly, ferromagnetic patterns on the sensor chip surface deflected the strong external fields, so that the large aggregation of magnetic particles on the sensor surface was reduced. We demonstrated using a single reusable SPR sensor chip to measure the nucleoprotein (NP) of H1N1 influenza virus solution ranging repeatedly for more than 7 times without significant signal degradation. Also, different target molecules could be repeatedly measured in a single SPR chip. Since our reusable SPR sensor chip can be repeatedly used in a conventional SPR system without any chemical processes for refreshment, the cost for SPR sensing should be significantly reduced. In this case, our reusable SPR sensor chip can be a major breakthrough and can be used for versatile practical applications of SPR sensors.
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http://dx.doi.org/10.1016/j.bios.2020.112561DOI Listing
November 2020

Ion-Selective Carbon Nanotube Field-Effect Transistors for Monitoring Drug Effects on Nicotinic Acetylcholine Receptor Activation in Live Cells.

Sensors (Basel) 2020 Jun 30;20(13). Epub 2020 Jun 30.

Department of Physics and Astronomy and Institute of Applied Physics, Seoul National University, Seoul 08826, Korea.

We developed ion-selective field-effect transistor (FET) sensors with floating electrodes for the monitoring of the potassium ion release by the stimulation of nicotinic acetylcholine receptors (nAChRs) on PC12 cells. Here, ion-selective valinomycin-polyvinyl chloride (PVC) membranes were coated on the floating electrode-based carbon nanotube (CNT) FETs to build the sensors. The sensors could selectively measure potassium ions with a minimum detection limit of 1 nM. We utilized the sensor for the real-time monitoring of the potassium ion released from a live cell stimulated by nicotine. Notably, this method also allowed us to quantitatively monitor the cell responses by agonists and antagonists of nAChRs. These results suggest that our ion-selective CNT-FET sensor has potential uses in biological and medical researches such as the monitoring of ion-channel activity and the screening of drugs.
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http://dx.doi.org/10.3390/s20133680DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7374424PMC
June 2020

Bioelectronic Skin Based on Nociceptive Ion Channel for Human-Like Perception of Cold Pains.

Small 2020 07 23;16(30):e2001469. Epub 2020 Jun 23.

Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, South Korea.

A bioelectronic skin device based on nociceptive ion channels in nanovesicles is developed for the detection of chemical cold-pain stimuli and cold environments just like human somesthetic sensory systems. The human transient receptor potential ankyrin 1 (hTRPA1) is involved in transmission and modulation of cold-pain sensations. In the bioelectronic skin, the nanovesicles containing the hTRPA1 nociceptive ion channel protein reacts to cold-pain stimuli, and it is electrically monitored through carbon nanotube transistor devices based on floating electrodes. The bioelectronic skin devices sensitively detect chemical cold-pain stimuli like cinnamaldehyde at 10 fm, and selectively discriminate cinnamaldehyde among other chemical stimuli. Further, the bioelectronic skin is used to evaluate the effect of cold environments on the response of the hTRPA1, finding that the nociceptive ion channel responds more sensitively to cinnamaldehyde at lower temperatures than at higher temperatures. The bioelectronic skin device could be useful for a basic study on somesthetic systems such as cold-pain sensation, and should be used for versatile applications such as screening of foods and drugs.
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http://dx.doi.org/10.1002/smll.202001469DOI Listing
July 2020

Micelle-stabilized Olfactory Receptors for a Bioelectronic Nose Detecting Butter Flavors in Real Fermented Alcoholic Beverages.

Sci Rep 2020 06 3;10(1):9064. Epub 2020 Jun 3.

Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea.

A bioelectronic nose device based on micelle-stabilized olfactory receptors is developed for the selective discrimination of a butter flavor substance in commercial fermented alcoholic beverages. In this work, we have successfully overexpressed ODR-10, a type of olfactory receptor, from Caenorhabditis elegans using a bacterial expression system at a low cost and high productivity. The highly-purified ODR-10 was stabilized in micelle structures, and it was immobilized on a carbon nanotube field-effect transistor to build a bioelectronic nose for the detection of diacetyl, a butter flavor substance, via the specific interaction between diacetyl and ODR-10. The bioelectronic nose device can sensitively detect diacetyl down to 10 fM, and selectively discriminate it from other substances. In addition, this sensor could directly evaluate diacetyl levels in a variety of real fermented alcoholic beverages such as beer, wine, and makgeolli (fermented Korean wine), while the sensor did not respond to soju (Korean style liquor without diacetyl). In this respect, our sensor should be a powerful tool for versatile food industrial applications such as the quality control of alcoholic beverages and foods.
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http://dx.doi.org/10.1038/s41598-020-65900-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7270175PMC
June 2020

Bioelectronic sensor mimicking the human neuroendocrine system for the detection of hypothalamic-pituitary-adrenal axis hormones in human blood.

Biosens Bioelectron 2020 Apr 3;154:112071. Epub 2020 Feb 3.

School of Chemical and Biological Engineering, Institute of Chemical Processes, Seoul National University, Seoul, 08826, Republic of Korea. Electronic address:

In the neuroendocrine system, corticotropin-releasing hormone (CRH) and adrenocorticotropic hormone (ACTH) play important roles in the regulation of the hypothalamic-pituitary-adrenal (HPA) system. Disorders of the HPA system lead to physiological problems, such as Addison's disease and Cushing's syndrome. Therefore, detection of CRH and ACTH is essential for diagnosing disorders related to the HPA system. Herein, receptors of the HPA axis were used to construct a bioelectronic sensor system for the detection of CRH and ACTH. The CRH receptor, corticotropin-releasing hormone receptor 1 (CRHR1), and the ACTH receptor, melanocortin 2 receptor (MC2R), were produced using an Escherichia coli expression system, and were reconstituted using nanodisc (ND) technology. The receptor-embedded NDs were immobilized on a floating electrode of a carbon nanotube field-effect transistor (CNT-FET). The constructed sensors sensitively detected CRH and ACTH to a concentration of 1 fM with high selectivity in real time. Furthermore, the reliable detection of CRH and ACTH in human plasma by the developed sensors demonstrated their potential in clinical and practical applications. These results indicate that CRHR1 and MC2R-based bioelectronic sensors can be applied for rapid and efficient detection of CRH and ACTH.
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http://dx.doi.org/10.1016/j.bios.2020.112071DOI Listing
April 2020

Long-Range Order Self-Assembly of Conjugated Block Copolymers at Inclined Air-Liquid Interfaces.

ACS Appl Mater Interfaces 2020 Jan 15;12(4):5099-5105. Epub 2020 Jan 15.

Department of Chemistry and Nanoscience , Ewha Womans University , 52 Ewhayeodae-gil , Seodaemun-gu, Seoul 03760 , Korea.

Here, we report that long-range order, direction-controlled, ultrathin conjugated polymer films can be formed by the self-assembly of conjugated block copolymers (i.e., poly(3-hexylthiophene)--poly(ethylene glycol)) at inclined air-water interfaces. Structure analyses revealed well-aligned nanowire arrays of poly(3-hexylthiophene) with a dramatically increased ordered domain size compared to the polymer films formed on a flat water surface. The improved degree of order was attributed to the flow field created by the enhanced solvent evaporation at the top of the water contact line. Note that it is challenging to prepare such well-ordered and molecularly thin films of conjugated polymers by conventional fabrication methods. The long-range order polymer film showed hole mobility an order of magnitude higher than polymer films formed on a flat interface when implemented as an active layer of field-effect transistor devices. This study demonstrates that a simple interface modification can significantly impact the self-assembly process, structure, and function of polymer films formed at the air-liquid interface.
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http://dx.doi.org/10.1021/acsami.9b20026DOI Listing
January 2020

Binary Self-Assembly of Conjugated Block Copolymers and Quantum Dots at the Air-Liquid Interface into Ordered Functional Nanoarrays.

ACS Appl Mater Interfaces 2019 Aug 25;11(31):28538-28545. Epub 2019 Jul 25.

Department of Chemistry and Nanoscience , Ewha Womans University , 52 Ewhayeodae-gil, Seodaemun-gu , Seoul 03760 , Korea.

Controlling the nanoscale morphology of conducting polymer/nanoparticle hybrid films is a highly desired but challenging task. Here, we report that such functional hybrid films with unprecedented structural order can be formed through the self-assembly of conjugated block copolymers and CdSe quantum dots at the air-water interface. The one-step assembly of quantum dots and block copolymers composed of polythiophene and polyethylene glycol (P3HT--PEG) at the fluidic interface generated a highly ordered assembly structure of P3HT nanowires and one-dimensional quantum dot arrays. Structure analyses revealed a unique self-assembly behavior and size dependency, which are distinct from the conventional self-assembly of coil-type polymers on solid substrates. Interestingly, hydrophobic quantum dots reside at the interface between P3HT and PEG domains without disrupting the P3HT packing structure, which is advantageous for the optoelectronic properties. Furthermore, large particles bridge the P3HT nanowires at both ends, while small particles decorate each P3HT/PEG interfaces, thus forming tight p-n junctions for a broad size range of nanoparticles. The nanoparticle-incorporated hybrid films showed more than an order of magnitude higher photocurrent and light sensitivity compared to polymer-only films, consistent with the assembly structure with close contact between the organic and inorganic semiconductors.
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http://dx.doi.org/10.1021/acsami.9b08892DOI Listing
August 2019

Nafion-Radical Hybrid Films on Carbon Nanotube Transistors for Monitoring Antipsychotic Drug Effects on Stimulated Dopamine Release.

ACS Appl Mater Interfaces 2019 Mar 27;11(10):9716-9723. Epub 2019 Feb 27.

We developed floating electrode-based carbon nanotube biosensors for the monitoring of antipsychotic drug effects on the dopamine release from PC12 cells under potassium stimulation. Here, carbon nanotube field-effect transistors with floating electrodes were functionalized with 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals by Nafion films. This method allows us to build selective biosensors for dopamine detection with a detection limit down to 10 nM even in the presence of other neurotransmitters such as glutamate and acetylcholine, resulting from the selective interaction between ABTS radicals and dopamine. The sensors were also utilized to monitor the real-time release of dopamine from PC12 cells upon the stimulation of high-concentrated potassium solutions. Significantly, the antipsychotic effects of pimozide on the dopamine release from potassium-stimulated PC12 cells could also be evaluated in a concentration-dependent manner by using the sensors. The quantitative and real-time evaluation capability of our strategy should provide a versatile tool for many biomedical studies and applications.
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http://dx.doi.org/10.1021/acsami.8b18752DOI Listing
March 2019

Electronic Traps and Their Correlations to Perovskite Solar Cell Performance via Compositional and Thermal Annealing Controls.

ACS Appl Mater Interfaces 2019 Feb 8;11(7):6907-6917. Epub 2019 Feb 8.

Herein, underlying factors for enabling efficient and stable performance of perovskite solar cells are studied through nanostructural controls of organic-inorganic halide perovskites. Namely, MAPbI, (FAMA)Pb(IBr), and (CsFAMA)Pb(IBr) perovskites (abbreviated as MA, FAMA, and CsFAMA, respectively) are examined with a grain growth control through thermal annealing. FAMA- and CsFAMA-based cells result in stable photovoltaic performance, while MA cells are sensitively dependent on the perovskite grain size dominated by annealing time. Micro-/nanoscopic features are comprehensively analyzed to unravel the origin that is directly correlated to the cell performance with the applications of electronic-trap characterizations such as photoconductive noise microscopy and capacitance analyses. It is revealed that CsFAMA has a lower trap density compared to MA and FAMA through the analyses of 1/ f noises and trapping/detrapping capacitances. Also, an open-circuit voltage ( V) change is correlated to the variation of trap states during the shelf-life test: FAMA and CsFAMA cells with the negligible change of V over weeks exhibit trap states shifting toward the band edge, although the power-conversion efficiencies are clearly reduced. The origins that critically affect the solar cell performance through the characterizations of shallow/deep traps with additional mobile defects in the perovskite and interfaces are discussed.
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http://dx.doi.org/10.1021/acsami.8b17431DOI Listing
February 2019

Nanoscale enhancement of photoconductivity by localized charge traps in the grain structures of monolayer MoS.

Sci Rep 2018 Oct 25;8(1):15822. Epub 2018 Oct 25.

Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea.

We report a method for mapping the nanoscale anomalous enhancement of photoconductivity by localized charge traps in the grain structures of a molybdenum disulfide (MoS) monolayer. In this work, a monolayer MoS film was laterally scanned by a nanoscale conducting probe that was used to make direct contact with the MoS surface. Electrical currents and noise maps were measured through the probe. By analyzing the data, we obtained maps for the sheet resistance and charge trap density for the MoS grain structures. The maps clearly show grains for which sheet resistance and charge trap density were lower than those of the grain boundaries. Interestingly, we found an unusual inverse proportionality between the sheet resistance and charge trap density in the grains, which originated from the unique role of sulfur vacancies acting as both charge hopping sites and traps in monolayer MoS. In addition, under light illumination, the larger the trap density of a region was, the larger the photocurrent of the region was, indicating anomalous enhancement of the photocurrent by traps. Since our method provides valuable insights to understand the nanoscale effects of traps on photoconductive charge transport, it can be a powerful tool for noise studies and the practical application of two-dimensional materials.
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http://dx.doi.org/10.1038/s41598-018-34209-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6202400PMC
October 2018

Human-like smelling of a rose scent using an olfactory receptor nanodisc-based bioelectronic nose.

Sci Rep 2018 09 17;8(1):13945. Epub 2018 Sep 17.

Department of Physics and Astronomy and Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea.

We report a strategy for the human-like smelling of a rose scent utilizing olfactory receptor nanodisc (ND)-based bioelectronic nose devices. In this strategy, a floating electrode (FE)-based carbon nanotube (CNT) field effect transistor (FET) was functionalized with human olfactory receptor 1A2 (hOR1A2)-embedded NDs (hOR1A2NDs). The hOR1A2NDs responded to rose scent molecules specifically, which were monitored electrically using the underlying CNT-FET. This strategy allowed us to quantitatively assess the contents of geraniol and citronellol, the main components of a rose scent, as low as 1 fM and 10 fM, respectively. In addition, it enabled us to selectively discriminate a specific rose odorant from other odorants. Significantly, we also demonstrated that the responses of hOR1A2NDs to a rose scent could be strongly enhanced by enhancer materials like a human nose. Furthermore, the method provided a means to quantitatively evaluate rose scent components in real samples such as rose oil. Since our method allows one to quantitatively evaluate general rose scent ingredients just like a human nose, it could be a powerful strategy for versatile basic research and various applications such as fragrance development.
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http://dx.doi.org/10.1038/s41598-018-32155-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6141559PMC
September 2018

Dye-functionalized Sol-gel Matrix on Carbon Nanotubes for Refreshable and Flexible Gas Sensors.

Sci Rep 2018 Aug 10;8(1):11958. Epub 2018 Aug 10.

Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul, 151-747, Republic of Korea.

We report a colorimetric dye-functionalized sol-gel matrix on carbon nanotubes for use as a refreshable and flexible gas sensor with humidity calibration. Here, we fabricated gas sensors by functionalizing dye molecules on the top of carbon nanotube networks via a sol-gel method. Using hybrid gas sensors with different dye molecules, we could selectively detect various hazardous gases, such as NH, Cl and SO gases, via optical and electrical signals. The sensors exhibited rather large conductance changes of more than 50% following exposure to gas species with concentrations even under the permissible exposure limit. Significantly, we could refresh used gas sensors by simply exposing them to fresh N gas without any heat treatment. Additionally, our sensors can be bent to form versatile practical sensor devices, such as tube-shape sensors for ventilation tubes. This work shows a simple but powerful method for building refreshable and selective gas sensors for versatile industrial and academic applications.
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http://dx.doi.org/10.1038/s41598-018-30481-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6086896PMC
August 2018

Nanoscale anomalous noise source switching with a trap-free current transition in a PEDOT:PSS film.

Nanotechnology 2018 Oct 1;29(42):425704. Epub 2018 Aug 1.

Department of Physics and Astronomy and Institute of Applied Physics, Seoul National University, Seoul 08826, Republic of Korea.

We imaged localized charge traps in a PEDOT:PSS film by using a scanning noise microscopy (SNM) system and observed anomalous noise source switching behaviors affecting the electrical characteristics of the film. The SNM system enabled us to measure the localized electrical current and noise maps of a PEDOT:PSS film with nanoscale resolution. The measured maps of the currents and noises were utilized to calculate effective charge trap densities in the film. As a result, we found non-homogeneous distributions of currents and effective charge trap densities on the localized area of the film due to the non-uniform distribution of PEDOT-rich and PSS-rich grains. At a low bias voltage, we observed high current levels and high charge trap densities in PEDOT-rich grains, while PSS-rich grains showed low-current levels and charge trap densities. Interestingly, the charge trap densities in both grains showed a noise source switching behavior with respect to the applied bias voltages, and the behavior strongly affected their electrical characteristic such as the trap-free transition of currents. These results indicate that the charge traps in a PEDOT:PSS film play an important role in the electrical characteristics of the films. Our observations provide a valuable insight on the understanding of the electrical characteristics of PEDOT:PSS films and an important guideline for its practical applications.
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http://dx.doi.org/10.1088/1361-6528/aad761DOI Listing
October 2018

Bioelectronic Nose Using Olfactory Receptor-Embedded Nanodiscs.

Methods Mol Biol 2018 ;1820:239-249

School of Chemical and Biological Engineering, Seoul National University, Seoul, South Korea.

Olfactory receptors (ORs) are the largest family of the G protein-coupled receptors (GPCRs), which are significantly involved in many human diseases and 40% of all drug targets. A platform containing stable and high-quality OR would be a powerful tool for the development of a practical biosensor that can be applied to various applications, such as the early diagnosis of diseases, assessment of food quality, and drug and fragrance development. Significant efforts have been made to develop the biosensor using GPCRs; nevertheless, they remain a challenge. This chapter describes an attractive methodology for the development of a stable bioelectronic nose using OR-embedded nanodiscs. The ORs were produced in Escherichia coli (E. coli), purified with column chromatography, reconstituted into nanodiscs and applied to a carbon nanotube-field effect transistor (CNT-FET) with floating electrodes. The nanodisc-based bioelectronic nose exhibits high-performance in terms of sensitivity, selectivity and stability. This strategy can be used as a practical method for the receptor-based sensing approach, which represents significant progress in nano-bio technology toward a practical biosensor.
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http://dx.doi.org/10.1007/978-1-4939-8609-5_18DOI Listing
March 2019

Mapping reversible photoswitching of molecular resistance fluctuations during the conformational transformation of azobenzene-terminated molecular switches.

Nanotechnology 2018 Sep 7;29(36):365704. Epub 2018 Jun 7.

Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul 08826, Republic of Korea.

We report a direct mapping and analysis of electrical noise in azobenzene-terminated molecular monolayers, revealing reversible photoswitching of the molecular resistance fluctuations in the layers. In this work, a conducting atomic force microscope combined with a homemade spectrum analyzer was used to image electrical current and noise at patterned self-assembled monolayers (SAMs) of azobenzene-terminated molecular wires on a gold substrate. We analyzed the current and noise imaging data to obtain maps of molecular resistances and amount of mean-square fluctuations in the resistances of the regions of trans-azobenzene and a cis/trans-azobenzene mixture. We revealed that the fluctuations in the molecular resistances in the SAMs were enhanced after the trans-to-cis isomerization, while the resistances were reduced. This result could be attributed to enhanced disorders in the molecular arrangements in the cis-SAMs. Furthermore, we observed that the changes in the resistance fluctuations were reversible with respect to repeated trans-to-cis and cis-to-trans isomerizations, indicating that the effects originated from reversible photoswitching of the molecular structures rather than irreversible damages of the molecules. These findings provide valuable insights into the electrical fluctuations in photoswitchable molecules, which could be utilized in further studies on molecular switches and molecular electronics in general.
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http://dx.doi.org/10.1088/1361-6528/aacb17DOI Listing
September 2018

Nanoscale "Noise-Source Switching" during the Optoelectronic Switching of Phase-Separated Polymer Nanocomposites.

Small 2018 Jun 27;14(25):e1800885. Epub 2018 May 27.

Department of Physics and Astronomy, Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea.

A method is developed to directly map nanoscale "noise-source switching" phenomena during the optoelectronic switching of phase-separated polymer nanocomposites of tetrathiafulvalene (TTF) and phenyl-C -butyric acid methyl ester (PCBM) molecules dispersed in a polystyrene (PS) matrix. In the method, electrical current and noise maps of the nanocomposite film are recorded using a conducting nanoprobe, enabling the mapping of a conductivity and a noise-source density. The results provide evidence for a repeated modulation in noise sources, a "noise-source switching," in each stage of a switching cycle. Interestingly, when the nanocomposite is "set" by a high bias, insulating PS-rich phases shows a drastic decrease in a noise-source density which becomes lower than that of conducting TTF-PCBM-rich phases. This can be attributed to a trap filling by charge carriers generated from a TTF (donor)-PCBM (acceptor) complex. In addition, when the film is exposed to UV, an optical switching occurs due to chemical reactions which lead to irreversible changes on the noise-source density and conductivity. The method provides a new insight on noise-source activities during the optoelectronic switching of polymer nanocomposites and thus can be a powerful tool for basic noise research and applications in organic memory devices.
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http://dx.doi.org/10.1002/smll.201800885DOI Listing
June 2018

High-Speed Lateral Flow Strategy for a Fast Biosensing with an Improved Selectivity and Binding Affinity.

Sensors (Basel) 2018 May 10;18(5). Epub 2018 May 10.

Department of Physics and Astronomy and Institute of Applied Physics, Seoul National University, Seoul 08826, Korea.

We report a high-speed lateral flow strategy for a fast biosensing with an improved selectivity and binding affinity even under harsh conditions. In this strategy, biosensors were fixed at a location away from the center of a round shape disk, and the disk was rotated to create the lateral flow of a target solution on the biosensors during the sensing measurements. Experimental results using the strategy showed high reaction speeds, high binding affinity, and low nonspecific adsorptions of target molecules to biosensors. Furthermore, binding affinity between target molecules and sensing molecules was enhanced even in harsh conditions such as low pH and low ionic strength conditions. These results show that the strategy can improve the performance of conventional biosensors by generating high-speed lateral flows on a biosensor surface. Therefore, our strategy can be utilized as a simple but powerful tool for versatile bio and medical applications.
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http://dx.doi.org/10.3390/s18051507DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5982462PMC
May 2018

Modified Floating Electrode-Based Sensors for the Quantitative Monitoring of Drug Effects on Cytokine Levels Related with Inflammatory Bowel Diseases.

ACS Appl Mater Interfaces 2018 May 9;10(20):17100-17106. Epub 2018 May 9.

Department of Internal Medicine and Healthcare Research Institute , Seoul National University Hospital Healthcare System Gangnam Center , Seoul 06236 , Korea.

Modified floating electrode-based sensors were developed to quantitatively monitor the levels of tumor necrosis factor α (TNF-α), a pro-inflammatory cytokine related with inflammatory bowel disease (IBD), and to evaluate the effect of drugs on the cytokine levels. Here, antibodies (anti-TNF-α) were immobilized on the floating electrodes of carbon nanotube devices, enabling selective and real-time detection of TNF-α among various cytokines linked to IBD. This sensor was able to measure the concentrations of TNF-α with a detection limit of 1 pg/L, allowing the quantitative estimation of TNF-α secretion from mouse macrophage Raw 264.7 cells stimulated by lipopolysaccharides (LPS). Notably, this method also allowed us to monitor the anti-inflammatory effect of a drug, lupeol, on the activation of the LPS-induced nuclear factor κB signaling in Raw 264.7 cells. These results indicate that our novel TNF sensor can be a versatile tool for biomedical research and clinical applications such as screening drug effects and monitoring inflammation levels.
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http://dx.doi.org/10.1021/acsami.8b04287DOI Listing
May 2018

Magnetically-focusing biochip structures for high-speed active biosensing with improved selectivity.

Nanotechnology 2018 Jun 6;29(26):265501. Epub 2018 Apr 6.

Department of Physics and Astronomy, and Institute of Applied Physics, Seoul national University, Seoul 08826, Republic of Korea.

We report a magnetically-focusing biochip structure enabling a single layered magnetic trap-and-release cycle for biosensors with an improved detection speed and selectivity. Here, magnetic beads functionalized with specific receptor molecules were utilized to trap target molecules in a solution and transport actively to and away from the sensor surfaces to enhance the detection speed and reduce the non-specific bindings, respectively. Using our method, we demonstrated the high speed detection of IL-13 antigens with the improved detection speed by more than an order of magnitude. Furthermore, the release step in our method was found to reduce the non-specific bindings and improve the selectivity and sensitivity of biosensors. This method is a simple but powerful strategy and should open up various applications such as ultra-fast biosensors for point-of-care services.
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http://dx.doi.org/10.1088/1361-6528/aabc4dDOI Listing
June 2018

Mapping nanoscale effects of localized noise-source activities on photoconductive charge transports in polymer-blend films.

Nanotechnology 2018 May 28;29(20):205204. Epub 2018 Feb 28.

We develolped a method to directly image the nanoscale effects of localized noise-source activities on photoconducting charge transports in domain structures of phase-separated polymer-blend films of Poly(9,9-di-n-octylfluorenyl-2,7-diyl) and Poly(9,9-di-n-octylfluorene-alt-benzothiadiazole). For the imaging, current and noise maps of the polymer-blend were recorded using a conducting nanoprobe in contact with the surface, enabling the conductivity (σ) and noise-source density (N ) mappings under an external stimulus. The blend-films exhibited the phase-separation between the constituent polymers at domains level. Within a domain, high σ (low N ) and low σ (high N ) regions were observed, which could be associated with the ordered and disordered regions of a domain. In the N maps, we observed that noise-sources strongly affected the conduction mechanism, resulting in a scaling behavior of σ ∝ [Formula: see text] in both ordered and disordered regions. When a blend film was under an influence of an external stimulus such as a high bias or an illumination, an increase in the σ was observed, but that also resulted in increases in the N as a trade-off. Interestingly, the Δσ versus ΔN plot exhibited an unusual scaling behavior of Δσ ∝ [Formula: see text] which is attributed to the de-trapping of carriers from deep traps by the external stimuli. In addition, we found that an external stimulus increased the conductivity at the interfaces without significantly increasing their N , which can be the origin of the superior performances of polymer-blend based devices. These results provide valuable insight about the effects of noise-sources on nanoscale optoelectronic properties in polymer-blend films, which can be an important guideline for improving devices based on polymer-blend.
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http://dx.doi.org/10.1088/1361-6528/aab2ddDOI Listing
May 2018

Fourier Transform Surface Plasmon Resonance of Nanodisks Embedded in Magnetic Nanorods.

Nano Lett 2018 03 12;18(3):1984-1992. Epub 2018 Feb 12.

Department of Physics and Astronomy and Institute of Applied Physics , Seoul National University , Seoul , 151-747 South Korea.

In this study, we demonstrate the synthesis and application of magnetic plasmonic gyro-nanodisks (GNDs) for Fourier transform surface plasmon resonance based biodetection. Plasmonically active and magnetically responsive gyro-nanodisks were synthesized using electrochemical methods with anodized aluminum templates. Due to the unique properties of GNDs (magnetic responsiveness and surface plasmon bands), periodic extinction signals were generated under an external rotating magnetic field, which is, in turn, converted into frequency domains using Fourier transformation. After the binding of a target on GNDs, an increase in the shear force causes a shift in the frequency domain, which allows us to investigate biodetection for HA1 (the influenza virus). Most importantly, by modulating the number and the location of plasmonic nanodisks (a method for controlling the hydrodynamic forces by rationally designing the nanomaterial architecture), we achieved enhanced biodetection sensitivity. We expect that our results will contribute to improved sensing module performance, as well as a better understanding of dynamic nanoparticle systems, by harnessing the perturbed periodic fluctuation of surface plasmon bands under the modulated magnetic field.
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http://dx.doi.org/10.1021/acs.nanolett.7b05439DOI Listing
March 2018

A triangle study of human, instrument and bioelectronic nose for non-destructive sensing of seafood freshness.

Sci Rep 2018 01 11;8(1):547. Epub 2018 Jan 11.

Department of Food and Nutrition, Myongji University, Yongin, Gyeonggi, 449-728, Republic of Korea.

Because the freshness of seafood determines its consumer preference and food safety, the rapid monitoring of seafood deterioration is considered essential. However, the conventional analysis of seafood deterioration using chromatography instruments and bacterial colony counting depends on time-consuming and food-destructive treatments. In this study, we demonstrate a non-destructive and rapid food freshness monitoring system by a triangular study of sensory evaluation, gas chromatography-mass spectroscopy (GC-MS), and a bioelectronic nose. The sensory evaluation indicated that the acceptability and flavor deteriorated gradually during post-harvest storage (4 °C) for 6 days. The GC-MS analysis recognized the reduction of freshness by detecting a generation of dimethyl sulfide (DMS) from the headspace of oyster in a refrigerator (4 °C) at 4 days post-harvest. However, the bioelectronic nose incorporating human olfactory receptor peptides with the carbon nanotube field-effect transistor sensed trimethylamine (TMA) from the oyster at 2 days post-harvest with suggesting early recognition of oysters' quality and freshness deterioration. Given that the bacterial species producing DMS or TMA along with toxins were found in the oyster, the bacterial contamination-driven food deterioration is rapidly monitored using the bioelectronic nose with a targeted non-destructive freshness marker.
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http://dx.doi.org/10.1038/s41598-017-19033-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5765080PMC
January 2018

Nanoscale Mapping of Molecular Vibrational Modes via Vibrational Noise Spectroscopy.

Nano Lett 2018 02 8;18(2):1001-1009. Epub 2018 Jan 8.

Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University , Seoul 08826, Korea.

We have developed a "vibrational noise spectroscopy (VNS)" method to identify and map vibrational modes of molecular wires on a solid substrate. In the method, electrical-noises generated in molecules on a conducting substrate were measured using a conducting atomic force microscopy (AFM) with a nanoresolution. We found that the bias voltage applied to the conducting AFM probe can stimulate specific vibrational modes of measured molecules, resulting in enhanced electrical noises. Thus, by analyzing noise-voltage spectra, we could identify various vibrational modes of the molecular wires on the substrates. Further, we could image the distribution of vibrational modes on molecule patterns on the substrates. In addition, we found that VNS imaging data could be further analyzed to quantitatively estimate the density of a specific vibrational mode in the layers of different molecular species. The VNS method allows one to measure molecular vibrational modes under ambient conditions with a nanoresolution, and thus it can be a powerful tool for nanoscale electronics and materials researches in general.
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http://dx.doi.org/10.1021/acs.nanolett.7b04457DOI Listing
February 2018

Fourier Transform Surface Plasmon Resonance (FTSPR) with Gyromagnetic Plasmonic Nanorods.

Angew Chem Int Ed Engl 2018 02 16;57(7):1841-1845. Epub 2018 Jan 16.

Department of Chemistry and Energy Science, Sungkyunkwan University, Suwon, 440-746, South Korea.

An unprecedented active and dynamic sensing platform based on a LSPR configuration that is modulated by using an external magnetic field is reported. Electrochemically synthesized Au/Fe/Au nanorods exhibited plasmonically active behavior through plasmonic coupling, and the middle ferromagnetic Fe block responded to a magnetic impetus, allowing the nanorods to be modulated. The shear force variation induced by the specific binding events between antigens and antibodies on the nanorod surface is used to enhance the sensitivity of detection of antigens in the plasmonics-based sensor application. As a proof-of-concept, influenza A virus (HA1) was used as a target protein. The limit of detection was enhanced by two orders of magnitude compared to that of traditional LSPR sensing.
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http://dx.doi.org/10.1002/anie.201710619DOI Listing
February 2018

Nanodisc-Based Bioelectronic Nose Using Olfactory Receptor Produced in Escherichia coli for the Assessment of the Death-Associated Odor Cadaverine.

ACS Nano 2017 12 13;11(12):11847-11855. Epub 2017 Nov 13.

School of Chemical and Biological Engineering, Seoul National University , Seoul 08826, Republic of Korea.

Cadaverine (CV), a death-associated odor, is an important target molecule for various sensor applications, including the evaluation of food spoilage. In this study, we developed an oriented nanodisc (ND)-functionalized bioelectronic nose (ONBN), based on carbon nanotube transistors and nanodiscs embedded with an olfactory receptor produced in Escherichia coli (E. coli) for detection of CV. To fabricate ONBN devices, a trace-amine-associated receptor 13c (TAAR13c) binding to CV was produced in E. coli, purified, reconstituted into NDs, and assembled, in the desired orientation, onto a carbon- nanotube-based field-effect transistor with floating electrodes. The ONBN showed high performance in terms of sensitivity and selectivity. Moreover, the ONBN was used to measure CV in diverse real-food samples for the determination of food freshness. These results indicate ONBN devices can be utilized to evaluate the quality of food samples quantitatively, which should enable versatile practical applications such as food safety and preservative development. Moreover, the ONBN could provide a useful tool for detection of corpses, which could be practically used in disaster responses.
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http://dx.doi.org/10.1021/acsnano.7b04992DOI Listing
December 2017

Transparent p-CuI/n-BaSnO heterojunctions with a high rectification ratio.

J Phys Condens Matter 2017 Sep 30;29(38):384004. Epub 2017 Jun 30.

Center for Novel States of Complex Materials Research, Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea.

Transparent p-CuI/n-BaSnO heterojunction diodes were successfully fabricated by the thermal evaporation of a (1 1 1) oriented γ-phase CuI film on top of an epitaxial BaSnO (0 0 1) film grown by the pulsed laser deposition. Upon the thickness of the CuI film being increased from 30 to 400 nm, the hole carrier density was systematically reduced from 6.0  ×  10 to 1.0  ×  10 cm and the corresponding rectification ratio of the pn diode was proportionally enhanced from ~10 to ~10. An energy band diagram exhibiting the type-II band alignment is proposed to describe the behavior of the heterojunction diode. A shift of a built-in potential caused by the hole carrier density change in the CuI film is attributed to the thickness-dependent rectification ratio. The best performing p-CuI/n-BaSnO diode exhibited a high current rectification ratio of 6.75  ×  10 at  ±2 V and an ideality factor of ~1.5.
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http://dx.doi.org/10.1088/1361-648X/aa7cbfDOI Listing
September 2017

Quantitative electrophysiological monitoring of anti-histamine drug effects on live cells via reusable sensor platforms.

Biosens Bioelectron 2017 Aug 31;94:707-713. Epub 2017 Mar 31.

Department of Physics and Astronomy and Institute of Applied Physics, Seoul National University, Seoul 08826, South Korea; Department of Biophysics and Chemical Biology, Seoul National University, Seoul 08826, South Korea. Electronic address:

We demonstrated the quantitative electrophysiological monitoring of histamine and anti-histamine drug effects on live cells via reusable sensor platforms based on carbon nanotube transistors. This method enabled us to monitor the real-time electrophysiological responses of a single HeLa cell to histamine with different concentrations. The measured electrophysiological responses were attributed to the activity of histamine type 1 receptors on a HeLa cell membrane by histamine. Furthermore, the effects of anti-histamine drugs such as cetirizine or chlorphenamine on the electrophysiological activities of HeLa cells were also evaluated quantitatively. Significantly, we utilized only a single device to monitor the responses of multiple HeLa cells to each drug, which allowed us to quantitatively analyze the antihistamine drug effects on live cells without errors from the device-to-device variation in device characteristics. Such quantitative evaluation capability of our method would promise versatile applications such as drug screening and nanoscale bio sensor researches.
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http://dx.doi.org/10.1016/j.bios.2017.03.063DOI Listing
August 2017

Air-Liquid Interfacial Self-Assembly of Non-Amphiphilic Poly(3-hexylthiophene) Homopolymers.

ACS Appl Mater Interfaces 2017 Apr 3;9(14):12865-12871. Epub 2017 Apr 3.

Department of Chemistry and Nano Science, Ewha Womans University , 52 Ewhayeodae-gil, Seodaemun-gu, Seoul 03760, Korea.

Here, we demonstrate that the self-assembly of poly(3-hexylthiophene) (P3HT) at the air-water interface can lead to free-standing films of densely packed P3HT nanowires. Interfacial self-assembly on various liquid subphases, such as water, diethylene glycol, and glycerol, indicates that the viscosity of the subphase is an important factor for the formation of well-ordered nanostructures. The thin-film morphology is also sensitive to the concentration of P3HT, its molecular weight (MW), and the presence of oxidative defects. The densely packed nanowire films can be easily transferred to solid substrates for device applications. The ultrathin films of P3HT prepared by the interfacial assembly showed significantly higher hole mobility (∼3.6 × 10 cm/V s) in a field-effect transistor than comparably thin spin-cast films. This work demonstrates that the air-liquid interfacial assembly is not limited to amphiphilic polymers and can, under optimized conditions, be applied to fabricate ultrathin films of widely used conjugated polymers with controlled morphologies.
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http://dx.doi.org/10.1021/acsami.7b01058DOI Listing
April 2017

Direct mapping of electrical noise sources in molecular wire-based devices.

Sci Rep 2017 02 24;7:43411. Epub 2017 Feb 24.

Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul 151-747, Korea.

We report a noise mapping strategy for the reliable identification and analysis of noise sources in molecular wire junctions. Here, different molecular wires were patterned on a gold substrate, and the current-noise map on the pattern was measured and analyzed, enabling the quantitative study of noise sources in the patterned molecular wires. The frequency spectra of the noise from the molecular wire junctions exhibited characteristic 1/f behavior, which was used to identify the electrical signals from molecular wires. This method was applied to analyze the molecular junctions comprising various thiol molecules on a gold substrate, revealing that the noise in the junctions mainly came from the fluctuation of the thiol bonds. Furthermore, we quantitatively compared the frequencies of such bond fluctuations in different molecular wire junctions and identified molecular wires with lower electrical noise, which can provide critical information for designing low-noise molecular electronic devices. Our method provides valuable insights regarding noise phenomena in molecular wires and can be a powerful tool for the development of molecular electronic devices.
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http://dx.doi.org/10.1038/srep43411DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5324066PMC
February 2017

Nanoscale hybrid systems based on carbon nanotubes for biological sensing and control.

Biosci Rep 2017 04 2;37(2). Epub 2017 Mar 2.

Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea

This paper provides a concise review on the recent development of nanoscale hybrid systems based on carbon nanotubes (CNTs) for biological sensing and control. CNT-based hybrid systems have been intensively studied for versatile applications of biological interfaces such as sensing, cell therapy and tissue regeneration. Recent advances in nanobiotechnology not only enable the fabrication of highly sensitive biosensors at nanoscale but also allow the applications in the controls of cell growth and differentiation. This review describes the fabrication methods of such CNT-based hybrid systems and their applications in biosensing and cell controls.
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http://dx.doi.org/10.1042/BSR20160330DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5483890PMC
April 2017