• Korean Chemical Engineering Research
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• v.46 no.2
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• pp.222-226
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• 2008

Nanoparticles have been developed and applied for various applications to intelligently deliver bioactive materials. Herein, lactocin was processed into nanoparticles with methacrylic acid-methyl methacrylate copolymer (1:1) (eudragit L100). The eudragit polymer can protect lactocin from the stomach acid and release lactocin in the intestines. When acetone and pH 7 buffer solution were used as non-solvent and solvent, respectively, the smallest volume-average particle size (290 nm) could be obtained. Freeze drying in presence of carrageenan (dispersant) can process the particles into dried powders with minimum aggregation. SEM observation revealed the primary particles prepared based on lactocin and eudragit were of a few tens of nanometers.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.8
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• pp.88-93
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• 2020

The goal of this study is to determine the influence of major factors on the spiral surface microparticle injection machining of cylindrical specimens by the statistical method ANOVA. Before the experiment, rod-shaped test specimens and jigs for helical surface spraying were prepared, and the surface roughness was measured with a surface roughness meter. The injection particle, nozzle diameter, and injection pressure were the primary parameters of the experiment. Other factors that were considered were injection height, injection time, revolutions, and feed distance. The surface roughness after machining was measured, and the effects of the surface roughness data on the primary factors were determined with ANOVA.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.3
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• pp.68-71
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• 2008

Transdermal and topical drug delivery with minimal tissue damage has been an area of vigorous research for a number of years. Our research team has initiated the development of an effective method for delivering drug particles across the skin (transdermal) for systemic circulation, and to localized (topical) areas. The device consists of a micro particle acceleration system based on laser ablation that can be integrated with endoscopic surgical techniques. A layer of micro particles is deposited on the surface of a thin metal foil. The rear side of the foil is irradiated with a laser beam, which generates a shockwave that travels through the foil. When the shockwave reaches the end of the foil, it is reflected as an expansion wave and causes instantaneous deformation of the foil in the opposite direction. Due to this sudden deformation, the microparticles are ejected from the foil at very high speeds, and therefore have sufficient momentum to penetrate soft body tissues. We have demonstrated this by successfully delivering cobalt particles $3\;{\mu}m$ in diameter into gelatin models that represent soft tissue with remarkable penetration depth.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.5
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• pp.223-227
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• 2009

$BaCO_3$ crystals with various morphology were prepared using precipitation, hydrothermal and ligand-assisted methods. An irregular structure of $BaCO_3$ microparticle was obtained by simple precipitation method from $Ba(NO_3)_2$ and $Na_2CO_3$ in aqueous solution. Hexagonal pyramidals of $BaCO_3$ were synthesized using a hydrothermal method between $Ba(NO_3)_2$ and urea. Hexagonal rods of $BaCO_3$ were also synthesized using the ligand-assisted hydrothermal method. The aspect ratio of $BaCO_3$ hexagonal rods was increased with the concentration of ligand.

• Polymer(Korea)
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• v.25 no.1
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• pp.41-48
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• 2001

Polyurethane(PU) microgels were synthesized from poly(caprolactone) diol(PCD) and/or poly(ethylene glycol)(PEG), diisocyanate and 1,2,6-hexane triol by solution polymerization method. A critical gelation concentration of the PU microgels with, mole ratios of PCD/PEG were the important factors influencing the formation and property microgel or macrogels. The physical and thermal properties of the PU microgels prepared with depending upon the structure of diisocyanate, mole ratio of PCD/PEG, and molecular weight of PEG were investigated. It was found that PU microgels were distributed by polydisperse, spherical small particles below 300nm and showed the properties of low viscosity.

• 한국연소학회:학술대회논문집
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• 2006.04a
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• pp.213-217
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• 2006

Recent advances in energetic materials modeling and high-resolution hydrocode simulation enable enhanced computational analysis of bio-medical treatments that utilize high-pressure shock waves. Of particular interest is in designing devices that use such technology in medical treatments. For example, the generated micro shock waves with peak pressure on orders of 10 GPa can be used for treatments such as kidney stone removal, trans-dermal micro-particle delivery. and cancer cell removal. In this work, we present a new computational methodology for applying the high explosive dynamics to bio-medical treatments by making use of high pressure shock physics and multi-material wave interactions. The preliminary calculations conducted by the in-house code, GIBBS2D, captures various features that are observed from the actual experiments under the similar test conditions. We expect to gain novel insights in applying explosive shock wave physics to the bio-medical science involving drug injection. Our forthcoming papers will illustrate the quantitative comparison of the modeled results against the experimental data.

• Korea-Australia Rheology Journal
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• v.19 no.3
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• pp.99-107
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• 2007

A nanofluid is a mixture of solid nanoparticles and a common base fluid. Nanofluids have shown great potential in improving the heat transfer properties of liquids. However, previous studies on the characteristics of nanofluids did not adequately explain the enhancement of heat transfer. This study examined the distribution of particles in a fluid and compared the mechanism for the enhancement of heat transfer in a nanofluid with that in a general microparticle suspension. A theoretical model was formulated with shear-induced particle migration, viscosity-induced particle migration, particle migration by Brownian motion, as well as the inertial migration of particles. The results of the simulation showed that there was no significant particle migration, with no change in particle concentration in the radial direction. A uniform particle concentration is very important in the heat transfer of a nanofluid. As the particle concentration and effective thermal conductivity at the wall region is lower than that of the bulk fluid, due to particle migration to the center of a microfluid, the addition of microparticles in a fluid does not affect the heat transfer properties of that fluid. However, in a nanofluid, particle migration to the center occurs quite slowly, and the particle migration flux is very small. Therefore, the effective thermal conductivity at the wall region increases with increasing addition of nanoparticles. This may be one reason why a nanofluid shows a good convective heat transfer performance.

• YAKHAK HOEJI
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• v.44 no.4
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• pp.293-299
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• 2000

Biodegradable microspheres made from poly-lactide-co-glycolide polymers have been considered as a new delivery system for single-dose vaccine. Purified tetanus toxoid (TT) was encapsulated in poly-lactide(PLA) and poly-lactide-co-glycolide (PLGA) microparticles using a solvent evaporation method in a multiple emulsion system (water-in oil-in water). The morphology of 77-loaded microparticles was spherical and the suface of them was smooth. The particle size was in a range of 2-10. Protein loading efficiency was 68-97.8%. PLGA (85:15) microparticle showed the highest efficiency. Protein release pattern was influenced by polymer molecular weight and composition. The release rate of PLA(Mw 100,000) microsphere was higher than any other microspheres. In consequence of the hydrolysis of PLGA(50:50) microspheres, environmental pH decreased from 7.4 to 5.0. The PLA, PLGA (75:25) and PLGA (85:15) microshperes showed no significant pH change. The antigenicity or n in microshperes was assayed by indirect sandwich ELISA using equine polyclonal tetanus antitoxin for capture antibody and human polyclonal tetanus antitoxin for primary antibody. The antigenicity of TT in PLA (Mw 100,000), PLGA(50:50, Mw 100,000) and PLGA (75:25, Mw 73,300) after 30 days incubation showed 54, 40.9 and 76.7%, respectively.

• Food Science and Biotechnology
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• v.17 no.4
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• pp.833-838
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• 2008

Size effects of rice product powders on physical properties including suspension stability were investigated in this study. Endosperm, bran, and husk powders of rice with different size particles were prepared using the pin crusher or the ultrafine air mill. The physical properties of the powders were examined using particle size analysis, scanning electron microscopy, and spectrophotometry. The peak of the volume-weighted particle distribution of ultrafine endosperm particles was at $5.4\;{\mu}m$ whereas those of the bran and the husk appeared at 65 and $35\;{\mu}m$, respectively. Ultrafine particles of the endosperm and the husks dispersed better than larger-sized particles. As time elapsed, the dispersibility decreased, but the ultrafine particles were precipitated at the slowest rate. Our results suggest that ultrafine particles, including future nanosized particles, provide improved solubility and dispersibility resulting in better stability in the food colloidal suspension.

• Journal of Korean Biological Nursing Science
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• v.24 no.4
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• pp.235-242
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• 2022

Purpose: To investigate associations of perceived stress level, serum cortisol level, and telomere length of community-dwelling adults in Korea. Methods: Data of a total of 135 community-dwelling adults aged over 40 years living in D metropolitan city from December 2020 to March 2021 were collected. Perceived stress level over the past month were measured using the Perceived Stress Score. Serum cortisol level was analyzed using a chemiluminescent microparticle immunoassay. Telomere length was determined using quantitative real-time polymerase chain reaction. The statistical package SPSS 23.0 was used to perform Chi-square test, independent t-test, and Pearson's correlation coefficient analysis. Results: There was no association between perceived stress and serum cortisol level (r = .07, p= .402). Serum cortisol level was not significantly associated with telomere length either (r = -.15, p= .081). However, the higher the perceived stress level, the shorter the telomere length (r= -.29, p= .001). Conclusion: These results suggest that perceived stress might induce physiological stress, which might partially affect gene biology. Further longitudinal research is needed to investigate the effect of perceived stress on telomere length. Intervention for relieving stress should be included in stabilizing the genetic environment of adults.