Hyejung Seo
Pohang University of Science and Technology
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Publication
Featured researches published by Hyejung Seo.
Journal of Physics D | 2009
Gyoo-Cheon Kim; Gook-Hee Kim; S. Park; Sangmin Jeon; Hyejung Seo; Felipe Iza; Jae Koo Lee
Ambient air plasmas have been known to kill cancer cells. To enhance selectivity we have used antibody-conjugated nanoparticles. We achieved five times enhancement of melanoma cell death over the case of the plasma alone by using an air plasma with gold nanoparticles bound to anti-FAK antibodies. Our results show that this new interdisciplinary technique has enormous potential for use as a complement to conventional therapies.
Analytical Chemistry | 2010
Jinmyoung Joo; Jongmin Shim; Hyejung Seo; Namchul Jung; Ulrich Wiesner; Jinwoo Lee; Sangmin Jeon
Ordered mesoporous TiO(2) was synthesized using the combined assembly of soft and hard chemistries method and deposited as a film coating on a microcantilever sensor array along with two other types of TiO(2) film: one from nanoparticles and one prepared via a sol-gel reaction. After loading methylene blue molecules on the TiO(2) films, the films were exposed to ultraviolet radiation. The photocatalytic decomposition of methylene blue was monitored by measuring changes in the resonance frequency of each cantilever. The mesoporous TiO(2) film showed higher photocatalytic activity than conventional TiO(2) films fabricated from nanoparticles or via a sol-gel reaction; this difference is attributed to the purely anatase crystalline morphology of the mesoporous TiO(2) film as well as its well-organized pore structure. The three-dimensionally interconnected pore network facilitates the diffusion of methylene blue molecules to the photocatalytically active sites of the mesoporous TiO(2).
Journal of Laboratory Automation | 2008
Yeolho Lee; Sangkyu Lee; Hyejung Seo; Sangmin Jeon; Wonkyu Moon
With a piezoelectric micro cantilever sensor, a biomarker for various cancers is detected up to the concentration level required to determine a disease by using the mass micro balancing whose principle is that change of mechanical vibrant frequency is measured due to a target material attached on a sensor structure. The used piezoelectric micro cantilever sensor is designed so as to have the sufficient values of mass sensitivity and reliability. The used piezoelectric film, which acts as both sensor and actuator, is a plumbum zirconate titanate (PZT). Geometrical dimension of the micro cantilever is 100 μm (length) by 30 μm (width) by 5 μm (thickness). The 50-μm-long PZT film with thickness of 2.5 μm is covered from its root to its middle. Carcinoembryonic antigen (CEA), the biomarker for testing the sensor as label-free detection for pathological tests, is known as a biomarker for various cancers. The critical value of CEA concentration is known as 30 pM (5 ng/mL), and it is detected by the binding of antigen and antibody from high concentration to the critical concentration. From the results, the sensor could be applied to label-free detection sensors for pathological tests.
Nanotechnology | 2010
Hyejung Seo; Jinmyoung Joo; Wooree Ko; Namchul Jung; Sangmin Jeon
A novel microgravimetric immunosensor has been developed using TiO(2) nanoparticle-modified immunoassay and silver enhancement reaction. An antibody-conjugated TiO(2) nanoparticle is bound to the AFP antigen immobilized on a quartz resonator. When the nanoparticles are exposed to UV light in a silver nitrate solution, the photocatalytic reduction of silver ions results in the formation of metallic silver onto the nanoparticles and induces a decrease in the resonance frequency. The frequency change by this photocatalytic reduction reaction is three orders of magnitude larger than the change by antigen binding alone. The efficiency of the photocatalytic reaction has been found to increase with the fraction of anatase crystallites in the nanoparticles and the concentration of the AgNO(3) solution. The results highlight the potential of the photocatalytic nanoparticles for the detection of low concentrations of target molecules using gravimetric sensors.
Chemical Communications | 2012
Dongkyu Lee; Donghoon Kwon; Wooree Ko; Jinmyoung Joo; Hyejung Seo; Soo Suk Lee; Sangmin Jeon
A rapid and facile signal enhancement method for detecting alpha-fetoprotein (AFP) was developed using the magnetic agglomeration of ferromagnetic nanoparticles and microcantilever sensors. The resonance frequency and deflection of the cantilevers were found to be more than 10-fold greater than that before physical agglomeration of the free nanoparticles around the magnetized nanoparticles.
ieee sensors | 2008
Yeolho Lee; Hyejung Seo; Sangmin Jeon; Wonkyu Moon
Using the piezoelectric micro cantilever sensor, biomarkers of various diseases are detected at their critical concentration or below. The detection principle of the sensor is the mass-micro-balancing technique that utilizes the change of the mechanical resonance frequency due to an object attached on a structure. An Ohm-contact electrode is installed to remove the parasitic capacitance effects between the electrodes in the sensor. The first resonant frequency of the piezoelectric micro cantilever can be monitored by measurement of the conductance component of the admittance. The results of the bio-marker-detection experiments show that the detection sensitivity of the micro cantilever is from 2 to 3 orders of magnitude higher than that of the conventional quartz-crystal micro-balancing detection.
Applied Physics Letters | 2012
Hyejung Seo; Wooree Ko; Sangmin Jeon
Large unilamellar vesicles were prepared for adsorption on quartz crystal surfaces coated with gold, mercaptoundecanoic acid, or octadecanethiol self-assembled monolayers. The adsorption of the vesicles onto these surfaces decreases the resonance frequency of the quartz crystals. We found that frequency changes due to vesicle adsorption were much lower in degassed than in air-rich water. Further, the vesicles adsorbed in air-rich water desorbed when the medium was replaced with degassed water, indicating that the presence of dissolved air in water played a key role in the adsorption and stability of vesicles.
Sensors and Actuators B-chemical | 2009
Dongkyu Lee; Myungsun Yoo; Hyejung Seo; Youngjo Tak; Wan-Gee Kim; Kijung Yong; Shi-Woo Rhee; Sangmin Jeon
Sensors and Actuators B-chemical | 2007
Hyejung Seo; Sunghye Jung; Sangmin Jeon
Macromolecules | 2008
Namchul Jung; Hyejung Seo; Dongkyu Lee; Chang Y. Ryu; Sangmin Jeon