Publications by authors named "Gyu-Hee Lee"

9 Publications

  • Page 1 of 1

Analysis of the Binding of Analyte-Receptor in a Micro-Fluidic Channel for a Biosensor based on Brownian Motion.

Micromachines (Basel) 2020 Jun 3;11(6). Epub 2020 Jun 3.

Dept. of Nano Manufacturing Technology, Korea Institute of Machinery and Materials, 156 Gajeongbuk-Ro, Yusung-Gu, Daejeon 34103, Korea.

This study experimentally analyses the binding characteristics of analytes mixed in liquid samples flowing along a micro-channel to the receptor fixed on the wall of the micro-channel to provide design tools and data for a microfluidic-based biosensor. The binding or detection characteristics are analyzed experimentally by counting the number of analytes bound to the receptor, with sample analyte concentration, sample flow rate, and the position of the receptor along the micro-channel length as the main variables. A mathematical model is also proposed to predict the number of analytes transported and bound to the receptor based on a probability density function for Brownian motion. The coefficient in the mathematical model is obtained by using a dimensionless mathematical model and the experimental results. The coefficient remains valid for all different conditions of the sample analyte concentration, flow rate, and the position of the receptor, which implies the possibility of deriving a generalized model. Based on the mathematical model derived from mathematical and experimental analysis on the detection characteristics of the microfluidic-based biosensor depending on previously mentioned variables and the height of the micro-channel, this study suggests a design for a microfluidic-based biosensor by predicting the binding efficiency according to the channel height. The results show the binding efficiency increases as the flow rate decreases and as the receptor is placed closer to the sample-injecting inlet, but is unaffected by sample concentration.
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http://dx.doi.org/10.3390/mi11060570DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7346006PMC
June 2020

Effect of Temperature on the Mechanical Properties and Polymerization Kinetics of Polyamide-6 Composites.

Polymers (Basel) 2020 May 15;12(5). Epub 2020 May 15.

Department of Mechanical System Engineering, Gyeongsang National University, 2, Tongyeonghaean-ro, Tongyeong-si, Gyeongsangnam-do 53064, Korea.

This work reports the preparation of carbon fiber reinforced thermoplastic composites via the in situ anionic ring opening polymerization of ε-caprolactam. Vacuum assisted resin transfer molding was used to fabricate polyamide-6/carbon fiber composites at different molding temperatures. As a result, the higher polymerization of ε-caprolactam was observed with the condition at 140 °C for satisfactory impregnation. Regarding molding temperature, the physical properties of polyamide-6/carbon fiber were observed that the bending and impact strengths at 140 °C were higher than those to at other molding temperatures. The polymerization kinetics of polyamide-6 was analyzed using differential scanning calorimetry by experimentally acquiring kinetic parameters according to model fitting approaches. Polymerization and crystallization, which occur simultaneously throughout the whole process, were separated using Gaussian and Maxwell-Boltzmann distributions to study polymerization kinetics. The result of the developed model was in good agreement with the experimental data for the presented first order autocatalytic reaction model.
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http://dx.doi.org/10.3390/polym12051133DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7284351PMC
May 2020

Residue analysis of tebufenozide and indoxacarb in chicken muscle, milk, egg and aquatic animal products using liquid chromatography-tandem mass spectrometry.

Biomed Chromatogr 2019 Jul 7;33(7):e4522. Epub 2019 Apr 7.

Department of Veterinary Pharmacology and Toxicology, College of Veterinary Medicine, Konkuk University, Seoul, Republic of Korea.

We developed an analytical method using liquid-liquid extraction (LLE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) to detect and quantify tebufenozide (TEB) and indoxacarb (IND) residues in animal and aquatic products (chicken muscle, milk, egg, eel, flatfish, and shrimp). The target compounds were extracted using 1% acetic acid (0.1% acetic acid for egg only) in acetonitrile and purified using n-hexane. The analytes were separated on a Gemini-NX C column using (a) distilled water with 0.1% formic acid and 5 mm ammonium acetate and (b) methanol with 0.1% formic acid as the mobile phase. All six-point matrix-matched calibration curves showed good linearity with coefficients of determination (R ) ≥0.9864 over a concentration range of 5-50 μg/kg. Intra- and inter-day accuracy was expressed as the recovery rate at three spiking levels and ranged between 73.22 and 114.93% in all matrices, with a relative standard deviation (RSD, corresponding to precision) ≤13.87%. The limits of quantification (LOQ) of all target analytes ranged from 2 to 20 μg/kg, which were substantially lower than the maximum residue limits (MRLs) specified by the regulatory agencies of different countries. All samples were collected from different markets in Seoul, Republic of Korea, and tested negative for tebufenozide and indoxacarb residues. These results show that the method developed is robust and may be a promising tool to detect trace levels of the target analytes in animal products.
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http://dx.doi.org/10.1002/bmc.4522DOI Listing
July 2019

Spherical Granule Production from Micronized Saltwort (Salicornia herbacea) Powder as Salt Substitute.

Prev Nutr Food Sci 2013 Mar;18(1):60-6

Department of Food Science and Biotechnology, Woosong University, Daejeon 300-718, Korea.

The whole saltwort plant (Salicornia herbacea) was micronized to develop the table salt substitute. The micronized powder was mixed with distilled water and made into a spherical granule by using the fluid-bed coater (SGMPDW). The SGMPDW had superior flowability to powder; however, it had low dispersibility. To increase the dispersibility of SGMPDW, the micronized powder was mixed with the solution, which contained various soluble solid contents of saltwort aqueous extract (SAE), and made into a spherical granule (SGMPSAE). The SGMPSAE prepared with the higher percentages of solid content of SAE showed improved dispersibility in water and an increase in salty taste. The SGMPSAE prepared with 10% SAE was shown to possess the best physicochemical properties and its relative saltiness compared to NaCl (0.39). In conclusion, SGMPSAEs can be used as a table salt substitute and a functional food material with enhanced absorptivity and convenience.
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http://dx.doi.org/10.3746/pnf.2013.18.1.060DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3867153PMC
March 2013

Volatile compounds of Panax ginseng C.A. Meyer cultured with different cultivation methods.

J Food Sci 2012 Jul 13;77(7):C805-10. Epub 2012 Jun 13.

Geumsan Ginseng and Medicinal Crop Experiment Station, CNARES, Geumsan 312-804, Korea.

The volatile compounds of Panax ginseng C.A. Meyer analyzed to interpret whether cultivation methods affect volatile compounds. The volatile compounds in Panax ginseng C.A. Meyer cultured with 3 different cultivation methods such as good agricultural practice, organic cultivation method, and general cultivation method were isolated by solid-phase microextraction fiber (polydimethylsiloxane 65 μm) and identified by gas chromatography mass spectrometry. Then, the scattering patterns of volatile compounds compared by principal component analysis. As the results, the 14 volatile compounds were identified from 30 ginseng samples and consisted mainly of sesquiterpene hydrocarbons. The differences among the different cultivation methods of the samples were obvious from the PC1 and PC2 scatter point plot. As the conclusion, the cultivation methods can affect to produce the volatile component of ginseng root. The organic and good agriculture practice cultivation can increase the ginseng characteristic volatile compounds.
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http://dx.doi.org/10.1111/j.1750-3841.2012.02765.xDOI Listing
July 2012

Characteristic aroma compounds of cooked and fermented soybean (Chungkook-Jang) inoculated with various Bacilli.

J Sci Food Agric 2013 Jan 12;93(1):85-92. Epub 2012 Jun 12.

Department of Food Science & Biotechnology, Woosong University, 17-2 Jayang-dong, Dong-ku, Daejeon 300-718, Korea.

Background: For selecting Chungkook-jang products with a less undesirable odour, the volatile compounds that affect the overall consumer acceptance of Chungkook-jang products were analysed. The volatile compounds of Chungkook-jang were extracted by using solid phase microextraction and direct solvent extraction and were detected by using gas chromatography-olfactometry. The results were represented as the mean of the log3 flavour dilution factors; principal component analysis was used to determine the effective components.

Results: Fifteen and 14 volatile compounds were detected in the extracts using solid phase microextraction and direct solvent extraction, respectively. The Bacillus species 2-M1L, which has the most overall acceptance, might have a nutty initial top note and nutty and cheesy long-lasting note aromas. In correlation analysis between the characteristic aromas and the overall acceptance, trimethyl pyrazine (nutty, pungent), butanoic acid (cheesy, butyric), and methyl pyrazine (burnt, roasted) were positively correlated with overall acceptance. In contrast, 3-hydroxy-2-butanone (buttery, fatty) and 2,3-butanediol (chemical, fatty) were negatively correlated with overall acceptance.

Conclusion: Consumers might prefer Chungkook-jang that has a more nutty and cheesy flavour and a less fatty one.
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http://dx.doi.org/10.1002/jsfa.5734DOI Listing
January 2013

Pinus densiflora leaf essential oil induces apoptosis via ROS generation and activation of caspases in YD-8 human oral cancer cells.

Int J Oncol 2012 Apr 11;40(4):1238-45. Epub 2011 Nov 11.

Department of Medical Genetic Engineering, Keimyung University School of Medicine, Daegu 704-701, Republic of Korea.

The leaf of Pinus (P.) densiflora, a pine tree widely distributed in Asian countries, has been used as a traditional medicine. In the present study, we investigated the anticancer activity of essential oil, extracted by steam distillation, from the leaf of P. densiflora in YD-8 human oral squamous cell carcinoma (OSCC) cells. Treatment of YD-8 cells with P. densiflora leaf essential oil (PLEO) at 60 µg/ml for 8 h strongly inhibited proliferation and survival and induced apoptosis. Notably, treatment with PLEO led to generation of ROS, activation of caspase-9, PARP cleavage, down-regulation of Bcl-2, and phosphorylation of ERK-1/2 and JNK-1/2 in YD-8 cells. Treatment with PLEO, however, did not affect the expression of Bax, XIAP and GRP78. Importantly, pharmaco-logical inhibition studies demonstrated that treatment with vitamin E (an anti-oxidant) or z-VAD-fmk (a pan-caspase inhibitor), but not with PD98059 (an ERK-1/2 inhibitor) or SP600125 (a JNK-1/2 inhibitor), strongly suppressed PLEO-induced apoptosis in YD-8 cells and reduction of their survival. Vitamin E treatment further blocked activation of caspase-9 and Bcl-2 down-regulation induced by PLEO. Thus, these results demonstrate firstly that PLEO has anti-proliferative, anti-survival and pro-apoptotic effects on YD-8 cells and the effects are largely due to the ROS-dependent activation of caspases.
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http://dx.doi.org/10.3892/ijo.2011.1263DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3584576PMC
April 2012

Volatile compounds and antimicrobial and antioxidant activities of the essential oils of the needles of Pinus densiflora and Pinus thunbergii.

J Sci Food Agric 2011 Mar 6;91(4):703-9. Epub 2011 Jan 6.

Seoul Metropolitan Government Research Institute of Public Health and Environment, Seoul 427-070, Korea.

Background: To investigate the volatile compounds and the antibacterial and antioxidant effects of the essential oils of Pinus densiflora needles (EPDN) and Pinus thunbergii needles (EPTN), the volatile compounds of steam-distilled essential oils were analysed by gas chromatography-mass spectrometry. Antibacterial activities were analysed by performing disc-agar diffusion assay and determining the minimum inhibitory concentrations (MICs) of the essential oils. Antioxidant activities were analysed via radical- and nitrite-scavenging activity assays.

Results: The yields of EPDN and EPTN were 0.304% (v/w) and 0.296% (v/w), respectively. In the antibacterial activity assay, the MICs of EPDN and EPTN for Klebsiella pneumoniae, Shigella flexneri and Proteus vulgaris were < 0.4 mg mL(-1) . In the antioxidant activity assay, the 50% inhibitory concentrations (IC(50) ) of EPDN and EPTN were 120 and 30 µg mL(-1) , respectively. At 1680 µg mL(-1) , both EPDN and EPTN exhibited > 50% nitrite-scavenging activity.

Conclusion: EPDN can be used as a natural antimicrobial substance.
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http://dx.doi.org/10.1002/jsfa.4239DOI Listing
March 2011

Production of spherical granule from viscous red ginseng extracts for improving product fluency and preservation and its physicochemical properties.

J Food Sci 2009 Nov-Dec;74(9):E519-25

School of Food Science and Biotechnology, Woosong Univ. 17-2, Jayang-dong Dong-ku, Daejon, 300-718, Korea.

Viscose red ginseng extracts dried and coated using fluidized bed coater may broaden their application in food processing industry and increasing the consumer acceptance. The operating conditions of fluidized bed coater were optimized for obtaining high yield and uniform spherical granule. The physicochemical properties and sensory characteristics among the concentrates, the fluidized bed dried core particle and the spherical granules of red ginseng extract were compared. The preservative properties of these materials were also analyzed. The predicted maximum yield of spherical granule was 85.42%, at a feeding rate (FR) of 111.04 mL/min, an atomization air pressure (AP) 275.30 kPa, and a product temperature (PT) of 68.53 degrees C. Most of ginsenosides, which were known as functional material, did not show significant changes after granulation, while the flowability and water solubility increased. Also, for a 10-mo storage at 30 degrees C, the spherical granule was the most stable among the materials considered. It can be concluded that the application of fluidized bed coater can be used for making the food product of viscous extracts more valuable.
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http://dx.doi.org/10.1111/j.1750-3841.2009.01361.xDOI Listing
September 2010