• Applied Biological Chemistry
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• v.49 no.4
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• pp.315-321
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• 2006

Inhibitors of acetylcholinesterase(AchE), such as organophosphates and carbamates, interfere the action of AchE in nerve and may lead to a severe impairment of nerve functions or even death. Therefore, insect AchE is the biological target of predominant insecticides used in agriculture. Biosensors are sensitive and can be used as dispoisable sensors for environmental control. In recent years, the use of AchEs in biosensor technology has gained enormous attention, in particular with respect to insecticide detection. The principle of biosensors using AchE as a biological recognition element is based on the inhibition the catalytic activity by the agents to be detected. We here present a strip-type biosensor based on AchE inhibition. In this study, acetylcholinesterase and PVA-SbQ(polyvinyl alcohol functionalized with methyl pyridinium methyl sulfate) were co-immobilized on immobilone-P membranes. Immobilization of the enzymes showed a stability in 6 months without activity loss in $4^{\circ}C$ storage. Enzymes immobilized on surfaces of membrane responded to organophosphates and carbamate more sensitivitive than enzyme in solution. Organophosphates and carbamates concentrations could be detected by entrapped and surface immobilized enzymes, in 5 min. For chlorpyrifos, carbofuran, cabaryl, and methidathion, the detection limits of AChE-strip were similar to that of HPLC/GC method.

• Korean Journal of Environmental Agriculture
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• v.29 no.1
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• pp.72-76
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• 2010

We have developed the bio-electrode measuring the variance of the amount of acetylcholine affected by residual pesticide. The working electrode of the biosensor was made by combination of cobalt phthalocyanine and carbon organic compounds. The biosensors were constructed by screen-printing method. The principle of working electrode is similar to thiocholine sensor. We have fabricated the biosensor using standard screen printing method. Generally, the biosensor made by printing method formed thick film biosensor. When the electrodes were made by electrochemical cells, the generation of current by the addition of enzyme substrate was inhibited by standard solutions of organo-phosphate pesticides. The detection limit of sensor is about 0.5 $\mu{g}/L$ for carbofuran. We could improve the responsibility of the sensor by controlling the cobalt phthalocyanine and thiocholine concentration ratio. Also we have tested the EPN and Chlorpyrifos pesticides and found that the biosensor is applicable to fast determination of residual pesticides.

• Journal of Plant Biotechnology
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• v.35 no.2
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• pp.141-145
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• 2008

In this study, glucose-inducible intergenic sequences were used to generate bioreporters of the cyanobacterium Synechocystis sp. PCC 6803 that could monitor environmental pollutants. Luciferase genes LuxAB from the marine bacterium Vibrio fischeri under the control of glucose-inducible intergenic seqeucens of eight genes (atpI, ndbA, ctaD1, tkt, pgi, pdh, ppc, and cydA) were successfully expressed in the cyano-bacterial transformants, showing 5-25 fold increases in biolumeniscence upon exposure to glucose. In addition, glucose-inducible cyanobacterial bioreporters were very sensitive to various chemicals such as heavy metals ($Hg^{2+}$, $Cu^{2+}$, $Zn^{2+}$), electron transport inhibitors (DCMU, DBMIB, $CN^-$), and antibiotics (chloramphenicol and rifampicin). These glucose-inducible cyanobacterial bioreporters would be useful to develop biosensors for rapid screening of environmental samples.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.7
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• pp.418-425
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• 2017

ZnO nanoparticles (ZnO NPs) are mainly used in semiconductors, solar cells, biosensors, and cosmetics (sunscreen). In this study, we investigated the behavior of ZnO NPs in aquatic and soil environments and their effects on plants (Artemisia annua L.) in hydroponic cultivation. It was confirmed that the ZnO NPs size increased and their dissolution decreased with increasing in pH. Leaching distance of ZnO NPs was less than 2.5 cm, indicating that ZnO NPs had a little potential to leach into deeper soil layers. When ZnO NPs were exposed to plant, the total weights of plants decreased. The effects on the length of root and shoot were not observed. In addition large amount of ZnO NPs were adsorbed on the surface of plant root and didn't translocate into shoot. These results suggest that ZnO NPs block the pores of the root cell wall and decrease the bioavailability of plant nutrients. Therefore it can be speculated that the particles increase in size and settle down in the water environment and may adversely affect the plant growth by firmly adhering to the root surface when the ZnO NPs are exposed to the environment.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.8
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• pp.900-906
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• 2005

The responses of two luminescence-based biosensors were studied on various heavy metals in aqueous solutions. One was recombinant E. coli ($DH5{\alpha}$/pSB311), genetically modified luminescence-based bacteria, and the other was Vibrio fisheri used for the LumisTox system. The recombinant E. coli was marked with the lux CDABE gene from multicopy plasmid, pACYC184, originally isolated from Photorhabdus luminescens. The $DH5{\alpha}$/pSB311 had a characteristic of no organic substrate for its luminescence reaction. Among the tested heavy metals Zinc and cadmium were less toxic than copper and mercury. The recombinant E. coli was more sensitive to toxicity of heavy metals than the LumisTox. The order of toxicity of the heavy metals to the recombinant E. coli was $Hg^{2+}>Cu^{2+}>Zn^{2+}>Cd^{2+}$. In case of the LumisTox, the order of the toxicity of heavy metals was $Hg^{2+}>Cu^{2+}>Cd^{2+}>Zn^{2+}$. The genetically modified luminescence-based biosensor offers a range of sensitive, rapid, and easy to use methods for assessing the potential toxicity of heavy metals in aqueous samples.

• Korean Journal of Microbiology
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• v.50 no.2
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• pp.128-136
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• 2014

Acyl homoserine lactone (AHL) lactonase has been proved to be the AHL-degrading enzyme with the highest substrate specificity for AHL molecules and has shown a considerable potential as low-cost and efficient quorum quenching (QQ) technique. However, few studies focused on its inhibitory effect on biofilm formation which is also a quorum sensing (QS)-regulated phenomenon. In this study, QQ activity of six isolates from biofouled reverse osmosis membranes was studied using Chromobacterium violaceum CV026 and Agrobacterium tumefaciens NTL4 as biosensors under various conditions. All of the isolates belonged to the genus Bacillus and showed QQ activity regardless of the acyl chain length or substitution of AHL molecule. The isolates were capable of significantly inhibiting biofilm formation (46.7-58.3%) by Pseudomonas aeruginosa PAO1 and produced heat-sensitive extracellular QQ substances. The LC-MS analysis of the QQ activity of a selected isolate, RO1S-5, revealed the degradation of N-(3-oxododecanoyl)-L-homoserine lactone (3-oxo-C12 AHL) and the production of corresponding acyl homoserine (3-oxo-C12-HS), which indicated the activity of AHL lactonase. The broad AHL substrate range and high substrate specificity suggested that the isolate would be useful for the control of biofilm-related pathogenesis and biofouling in industrial processes.

• Korean Chemical Engineering Research
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• v.55 no.1
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• pp.115-120
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• 2017

In recent, it is worldwide issued that nanoscale science and technology as a solution have supported to increase the sensing performance in carbon nanotube based biosensor system. Containing material chemistry in various nanostructures has formed their high potentials for stabilizing and activating biocatalyst as a bioreceptor for medical, food contaminants, and environmental detections using electrode modification technologies. Especially, the large surface area provides the attachment of biocatalysts increasing the biocatalyst loading. Therefore, nano-scale engineering of the biocatalysts have been suggested to be the next stage advancement of biosensors. Here, we would like to study the electrical mechanism depending on the exposure methods (soaking or dropping) to the sample solution to the assembled carbon nanotubes (CNTs) on the gold electrodes of biosensor for a simple and highly sensitive detection. We performed various experiments using polar and non-polar solutions as sampling tests and identified electrical response of assembled CNTs in those solutions.

• Journal of the Korean Electrochemical Society
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• v.23 no.3
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• pp.73-80
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• 2020

Fenton oxidation method using hydrogen peroxide is an eco-friendly oxidation method used in water treatment and soil restoration. When removing pollutants by this method, it is quite important to properly regulate the concentration of hydrogen peroxide according to the concentration of the contaminants. In this study, electrochemical biosensors using HRP (horseradish peroxidase) enzymes were manufactured and studies were conducted on the activity of enzymes and the detection characteristics of hydrogen peroxide. HRP were electro deposited with chitosan and AuNP on the working electrode surface of the SPCE (Screen Printed Carbon Electrode). Then, the fixation of enzymes was confirmed using the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The activity of HRP enzymes was also identified from chronoamperometry (CA) and UV spectroscopy. After immersing the biosensor in PBS solution the current generated from electrodes by titrating hydrogen peroxide was measured from CA analysis. The generated current increased linearly for the concentration of hydrogen peroxide, and a calibration curve was derived that could predict the concentration of hydrogen peroxide from the current.

• Journal of Life Science
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• v.21 no.9
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• pp.1323-1328
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• 2011

We herein report the development of an agarose-gel-immobilized recombinant bacterial biosensor simple system for the field monitoring of phenolic compounds. Escherichia coli cells harboring the pLZCapR plasmid, which was previously designed to express the ${\beta}$-galactosidase reporter gene in the presence of phenolic compounds, were co-immobilized with a substrate [chlorophenol red ${\beta}$-galactopyranoside (CPRG) in agarose gel, and dispensed to the wells of a 96-well plate. Field samples were added to the wells and color development was monitored. In the presence of 5 ${\mu}M$ to 10 mM of phenol, the biosensor developed a red (representing hydrolysis of CPRG) color. Other phenolic compounds were also detected by this immobilized system, with the pattern resembling that previously reported for the corresponding non-immobilized biosensor. The immobilized cells showed optimum activity when the gel was simultaneously supplemented with 6% dimethyl formamide (DMF), 0.1% SDS and 10 mM $CaCl_2$. The immobilized biosensor described herein does not require the addition of a substrate or the use of unwieldy instruments or sample pretreatments that could complicate field studies.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.281.2-281.2
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• 2013

Since heavy metal ions included in water or food resources have critical effects on human health, highly sensitive, rapid and selective analysis for heavy metal detection has been extensively explored by means of electrochemical, optical and colorimetric methods. For example, quantum dots (QDs), such as semiconductor QDs, have received enormous attention due to extraordinary optical properties including high fluorescence intensity and its narrow emission peaks, and have been utilized for heavy metal ion detection. However, the semiconductor QDs have a drawback of serious toxicity derived from cadmium, lead and other lethal elements, thereby limiting its application in the environmental screening system. On the other hand, Graphene oxide (GO) has proven its superlative properties of biocompatibility, unique photoluminescence (PL), good quenching efficiency and facile surface modification. Recently, the size of GO was controlled to a few nanometers, enhancing its optical properties to be applied for biological or chemical sensors. Interestingly, the presence of various oxygenous functional groups of GO contributes to opening the band gap of graphene, resulting in a unique PL emission pattern, and the control of the sp2 domain in the sp3 matrix of GO can tune the PL intensity as well as the PL emission wavelength. Herein, we reported a photoluminescent GO array on which heavy metal ion-specific DNA aptamers were immobilized, and sensitive and multiplex heavy metal ion detection was performed utilizing fluorescence resonance energy transfer (FRET) between the photoluminescent monolayered GO and the captured metal ion.