• Journal of the Korean Applied Science and Technology
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• v.28 no.1
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• pp.15-21
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• 2011

Threelectrodes systems were used in stripping voltammetry (SW) and cyclic voltammetry (CV) instead of the expensive platinum and Ag/AgCl reference electrodes. Moreover, the electrolyte solution was used with deep seawater, which can reduce water pollution, is more eco-friendly, and has a lower cost. The analytical optimum parameters measured via CV and SW and with working ranges were obtained from 10 to 80 ug/L using fluorine immobilized on a graphite pencil electrode (FE). Under the optimum conditions, the analytical detection limit of 6.30 ug/LAu was obtained. The results of the study can be applied to diagnostic assay for natural minerals and human finger tissue.

• Journal of Microbiology and Biotechnology
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• v.7 no.4
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• pp.242-249
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• 1997

Stability of bioluminescence was investigated with Photobacterium phosphoreum immobilized on the strontium alginate in order to develope continuous real time monitoring of pollutants. The stability of bioluminescence emission was improved by prolonged aging time. The aging time of ${\geq}40$ min and the cell concentration of ${\leq}0.6\;of\;OD_660$ were selected for the immobilization of P. phosphoreum to give linearity between cell concentrations and bioluminescence intensity. In sensitivity tests using phenol, it was found that this compound quenched bioluminescence proportional to the concentration without lowering of cell growth. The lower value for maximum quenching ($q_s$) and higher dissociation constant ($K_s$) were observed with strontium-alginate immobilized cells compared to free cells. The response of bioluminescence to toxicants was evaluated with the immobilized luminescent bacteria. The sensitivity of the immobilized cells was found to be good in response to toxicants, 4-nitrophenol, salicylate and cadmium, when evaluated with a specific rate of bioluminescence quenching.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1223-1224
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• 2015

Recently, Alzheimer's Disease (AD) is one of the biggest threats to healthy society. Current medical AD diagnosis depends on interviews and the molecular neuroimaging. There is no cure for the disease, which worsens as it progresses, and eventually leads to death. Amyloid ${\beta}$ and Tau-meditated neuronal injury and dysfunction are candidates of biomarker for AD diagnosis using blood. For highly sensitive and selective biosensor platform, interdigitated microelectrodes (IMEs) sensor was prepared with micro fabrication process and Amyloid ${\beta}$ antibody. Amyloid ${\beta}$ concentration of 1, 10, 100, and 1000 pg/mL was injected in reaction chamber with IME sensors, impedance and conductance of IMEs changed respectively. These results show our newly proposed IMEs sensor can be usefully utilized for AD early diagnosis.

• Journal of the Korean Applied Science and Technology
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• v.30 no.2
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• pp.197-203
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• 2013

The diagnostic assay of calcium ion was sought using a modified sensor with square-wave stripping voltammetry (SWSV) and cyclic voltammetry (CV). In this study, simple graphite pencil was used as working, reference, and auxiliary electrodes. By coating the working electrodes with DNA, their sensitivity was very much improved, and good results were yielded. Moreover, clean seawater was used as an electrolyte solution instead of acid and base electrolytes to lessen the expenses involved in the experiment. The analytical optimum conditions were also examined. These conditions were attained at the low detection limit of $0.6ugL^1$. After that, the results were applied to drinking water of milk contain.

• Journal of the Korean Applied Science and Technology
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• v.31 no.4
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• pp.663-668
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• 2014

An in-vivo diagnosis of trace Mg(II) ion was performed using a low-cost and environment-friendly voltammetric method, using a graphite counter and reference electrodes and a fluorine-immobilized graphite working electrode, and clean deep seawater was used as an electrolyte solution. Under optimum conditions, the analytical working ranges attained microgram ranges, and a detection limit of $80.6ugL^{-1}$ was obtained using stripping voltammety with 60 sec accumulation time. Ex-vivo application was performed on fish liver and mice droppings. The developed techniques can be applicable to tumor cell analysis.

• Journal of Biosystems Engineering
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• v.30 no.2 s.109
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• pp.114-120
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• 2005

In this study, a biological reaction and measurement control system was developed to rapidly measure the insecticide imidacloprid residues in agricultural products. The biological reaction part of the system was designed to include micro-pumps and valves for fluid transport, and a polystyrene covet as a reaction chamber. The measurement control part of the system consisted of a photodiode with a light-emitting diode for optical density measurement, and a control microcomputer to implement assay. Signal output was read as the rate of change in optical density at 645 nm. The sensitivity of the system was 2.2 ng/mL ($IC_50$). The system could execute a measurement cycle in about 19 minutes. Research will be continued to develop an automatic sampler fur imidacloprid residues from agricultural products.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.10
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• pp.449-452
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• 2005

We fabricated an electrochemical detector (ECD) to catalyze redox reaction efficiently by electrodepositing Prussian blue (PB) on the indium tin oxide (ITO) electrode. Capillary electrophoresis (CE) and amperometric method were used. We investigated the PB surface properties by topography from atomic force microscopy (AFM). Also PB film thickness calibration with respect to deposition time and voltage was used to get better PB surFace. The PB thin film of dense and smooth surface could catalyze redox reaction efficiently. Comparing with CE-ECD microchip using bare-lTO electrode, proposed CE-ECD microchip using PB deposited electrode has shown better sensitivity by determining the detected peak current from the electropherograms while the concentration of tested analyzes was maintained the same. It is verified that detection limit can be lowered for 0.01 mM of dopamine and catechol respectively.

• Bulletin of the Korean Chemical Society
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• v.18 no.11
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• pp.1149-1152
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• 1997

An enzyme electrode for the amperometric measurement of urea was prepared by co-immobilizing L-glutamate dehydrogenase and urease onto an Immobilon-AV affinity membrane attached to a glassy carbon electrode. The reduced nicotinamide adenine dinucleotide(NADH) was used as the electroactive species. The electrochemical oxidation of NADH was monitored at +1.0 volt vs. Ag/AgCl. The enzyme-immobilized electrode was linear over the range of 2.0 × 10-5 to 2 × 10-4 M. The response time of the electrode was approximately 3 min. and the optimum pH of the enzyme immobilized membrane was pH 7.4-7.6 (Dulbcco's buffer solution). It was stable for at least two weeks or 50 assays. There was no interference from other physiological species, except from high levels of ascorbic acid.

• Journal of Applied Biological Chemistry
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• v.44 no.4
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• pp.163-166
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• 2001

Piezoelectric (PZ) crystal biosensor system was used to detect the DNA of food pathogenic Listeria monocytogenes. L. monocytogenes-specific DNA was multiplied via the polymerase chain reaction using LM1 oligonucleotide (5'-TTACGAATTAAAAAGGAGCG-3') and LM2 oligonucleotide (5'-TTAAATCAGCAGGGGTCTTT-3') as primers. DNA fragment of 161 bp, which was specific only for L. monocytogenes, was observed. To obtain a large amount of single-stranded DNA containing an SH group used for coupling to the gold electrode chemisorptively, LM1 oligonucleotide containing a mercaptohexyl group was utilized as a single strand PCR primer. The PCR product was immobilized onto the gold electrode of PZ crystal, and hybridization was monitored in quartz crystal microbalance (QCM) system by injecting the antisense single-stranded DNA of 161 nucleotides obtained via the single strand PCR using the unmodified LM2 primer. Approximately 70 Hz of frequency drop was observed in the QCM system in the case of two consecutive injections of $5{\mu}g$ of the antisense single-stranded DNA.

• Bulletin of the Korean Chemical Society
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• v.32 no.6
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• pp.1975-1979
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• 2011

The modification of a gas diffusion layer (GDL), a vital component in polymer electrolyte fuel cells, is described here for use in the electrochemical detection of antibody-antigen biosensors. Compared to other substrates (gold foil and graphite), mouse anti-rHBsAg monoclonal antibody immobilized on gold-coated GDL (G-GDL) detected analytes of goat anti-mouse IgG antibody-ALP using a relatively low potential (-0.0021 V vs. Ag/AgCl 3 M NaCl), indicating that undesired by-reactions during electrochemical sensing should be avoided with G-GDL. The dependency of the signal against the concentration of analytes was observed, demonstrating the possibility of quantitative electrochemical biosensors based on G-GDL substrates. When a sandwich method was employed, target antigens of rHBsAg with a concentration as low as 500 ng/mL were clearly measured. The detection limit of rHBsAg was significantly improved to 10 ng/mL when higher concentrations of the 4-aminophenylphosphate monosodium salt (APP) acting on substrates were used for generating a redox-active product. Additionally, it was shown that a BSA blocking layer was essential in improving the detection limit in the G-GDL biosensor.