• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1629-1632
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• 2008

Rapid, real-time detection of pathogenic microorganisms is an emerging and quickly evolving field of research, especially with regard to microorganisms that pose a major threat to public health. Herein, a new method that uses bioimpedance and solid culture medium for the real-time detection of microorganisms is introduced. We fabricated a new impedimetric biosensor by integrating solid media and two plane electrodes attached on two facing sides of an acryl well. During bioelectrical impedance analysis, the solid medium showed the characteristics of a homogenous conductive material. In a real-time impedance measurement, our solid-medium biosensor could monitor bacterial growth in situ with a detection time of ${\sim}4$ hrs. Our data indicate that the solid-medium biosensor is useful for detecting airborne microorganisms, thereby providing a new analytical tool for impedance microbiology.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.30 no.4 s.48
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• pp.549-553
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• 2004

ATP bioluminescence system and impedance system were evaluated with the objective of reducing the time for microbial analysis of cosmetics formulations from 72 to 24 h. The meaningful correlation (at least $95\%$) was achieved when emulsion were artificially contaminated with low levels of different organisms, including Pseudomonas aeruinosa, Staphylococcus aureus, Escherichia coli and Ralstonia mannitolilytica. The standard agar plate method, ATP bioluminescence and impedance method were used for in this study. Successful evaluation and validation of automated systems has enabled the introduction of ATP bioluminescence and impedance method into routine use within the microbiology laboratory. This has provided a rapid assessment of product quality, resulting in faster throughput and resource maximization.

• Journal of Microbiology and Biotechnology
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• v.18 no.1
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• pp.145-152
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• 2008

A cell-based in vitro exposure system was developed to determine whether oxidative stress plays a role in the cytotoxic effects of volatile organic compounds (VOCs) such as benzene, toluene, xylene, and chlorobenzene, using human epithelial HeLa cells. Thin films based on cysteine-terminated synthetic oligopeptides were fabricated for immobilization of the HeLa cells on a gold (Au) substrate. In addition, an immobilized cell-based sensor was applied to the electrochemical detection of the VOCs. Layer formation and immobilization of the cells were investigated with surface plasmon resonance (SPR), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The adhered living cells were exposed to VOCs; this caused a change in the SPR angle and the VOC-specific electrochemical signal. In addition, VOC toxicity was found to correlate with the degree of nitric oxide (NO) generation and EIS. The primary reason for the marked increase in impedance was the change of aqueous electrolyte composition as a result of cell responses. The p53 and NF-${\kappa}B $ downregulation were closely related to the magnitude of growth inhibition associated with increasing concentrations of each VOC. Therefore, the proposed cell immobilization method, using a self-assembly technique and VOC-specific electrochemical signals, can be applied to construct a cell microarray for onsite VOC monitoring.

• Journal of Radiation Protection and Research
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• v.38 no.4
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• pp.202-207
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• 2013

Bioimpedance involves a lot of information related to living tissue. If there is alteration in bio tissue, its electrical characteristics also change. It is to study electrical characteristics of pork tenderlion in using a HP-4194A Impedance/Gain-phase analyzer instrument and electrical characteristics changes by graded radiation exposure dose. The results were as follow 1. Electrical characteristics of pork tenderlion in repeated measurement had high precision within ${\pm}5$% of coefficiency of variability. 2. During the measurement impedance absolute value and phase alteration did not show statistically significant difference.(p>0.05) 3. While impedance phase of electrical characteristics associated with frequency change was almost stable, impedance absolute value was in inverse proportion to frequency that means high inverse correlation of -0.096(r). 4. Impedance absolute value dropped in radiation exposure dose. The alteration of the value did not show statistically significant difference in 1 Gy, 2 Gy and 4 Gy.(p>0.05) However in radiation exposure dose of 10 Gy, the decrease of impedance absolute value was significantly different.(p<0.05) 5. Impedance phase according to radiation exposure dose change did not show statistically significant difference in 1 Gy, 2 Gy, 4 Gy, and 10 Gy(p>0.05).

• Journal of Sensor Science and Technology
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• v.17 no.3
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• pp.195-202
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• 2008

A biosensor based on the measurement of capacitance changes has been designed and fabricated for simple and realtime detection of bacteria. Compared to an impedance measurement technique, the capacitance measurement can make additional measurement circuits simpler, which improves a compatability for integration between the sensor and circuit. The fabricated sensor was characterized by detecting Escherichia coli(E. coli). The capacitance changes measured by the sensor were proportional to E. coli cell density, and the proposed sensor could detect $1{\times}10^6$ cfu/ml E. coli at least. The real-time detection was verified by measuring the capacitance every 20 minutes. After 7 hours of E. coli growth experiment, the capacitance of the sensor in the micro volume well with $4.5{\times}10^5$ cfu/ml of initial E. coli density increased by 20 pF, and that in another wells with $1.5{\times}10^6$ cfu/ml and $8.5{\times}10^7$ cfu/ml initial E. coli density increased by 56 pF and 71 pF, respectively. The proposed sensor has a possibility of the real-time detection for bacterial growth, and can detect E. coli cells with $1.8{\times}10^5$ cfu in nutrient broth in 5 hours.

• Journal of Microbiology and Biotechnology
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• v.23 no.1
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• pp.36-39
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• 2013

We introduce a high-performance microbial fuel cell (MFC) that was operated using a 0.1M bicarbonate buffer as the cathodic electrolyte. The MFC had a 136.42 $mW/m^2$ maximum power density under continuous feeding of 5 mM acetate as fuel. Results of the electrode potential measurements showed that the cathode potential of the bicarbonate-buffered condition was higher than the phosphate-buffered condition, although the phosphate condition had less interfacial resistance between the membrane and electrolyte. Therefore, we posit here that the increased power of the bicarbonate-buffered MFC may be caused by the higher cathode potential rather than by the interfacial membrane-electrolyte resistance.

• Journal of Food Hygiene and Safety
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• v.32 no.2
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• pp.83-88
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• 2017

We introduced disposable amperometric immunosensors for the detection of Sildenafil and Vardenafil (SDF/VDF) based on screen printed carbon electrodes. The developed immunosensors were used as a non-competitive sandwich-type enzyme immunoassay with a horseradish peroxidase label. The sensors were constructed on screen printed carbon electrodes by the simple electrochemical deposition of a reduced graphene oxide and chitosan (ErGO-CS) composite. To evaluate the sensing chemistry and optimize the sensor characteristics, a series of electrochemical experiments were carried out including electrochemical impedance spectroscopy, cyclic voltammetry and amperometry. The sensors showed a linear response to SDF/VDF concentrations in a range from 100 pg/mL to 300 ng/mL. The lower detection limit was calculated to be 55 pg/mL, the sensitivity was calculated to be $1.02{\mu}Ang/mL/cm^2$, and the sensor performance exhibited good reproducibility with a relative standard deviation (RSD) of 7.1%. The proposed sensing chemistry strategy and the sensor format can be used as a simple, cost-effective, and feasible method for the in-field analysis of SDF/VDF in functional or health supplement food samples.