• Carbon letters
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• v.13 no.3
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• pp.173-177
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• 2012

A drug delivery system (DDS) was prepared with a temperature and pH-responsive hydrogel. Poly(vinyl alcohol) (PVA)/poly(acrylic acid) (PAAc)/poly(N-isopropylacrylamide) (PNIPAAm)/multi-walled carbon nanotube (MWCNT) nanocomposites were prepared by radical polymerization for the temperature and pH-responsive hydrogels. MWCNTs were employed to improve both the thermal conductivity and mechanical properties of the PVA/PAAc/PNIPAAm/MWCNT nanocomposite hydrogels. Various amounts of MWCNTs (0, 0.5, 1 and 3 wt%) were added to the nanocomposite hydrogels. PVA/PAAc/PNIPAAm/MWCNT nanocomposite hydrogels were characterized with a scanning electron microscope. The mechanical properties were measured with a universal testing machine. Swelling and releasing properties of nanocomposite hydrogels were investigated at various temperatures and pHs. Temperature and pH-responsive release behavior was found to be dependent on the content of MWCNTs in nanocomposite hydrogels.

• Polymer(Korea)
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• v.32 no.4
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• pp.397-402
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• 2008

Perfluoropolyether(PFPE) has been widely applied in industry because of its very excellent properties of very high contact angle and low surface energy, good lubricant property and antifouling property. But the difficulty to synthesize PFPE has limited the research on this field. In this study, the novel silicon-containing oligomer with perfluoropolyether moiety was synthesized, and the structure was characterized by $^{19}F$-NMR and $^1H$-NMR. The surface properties of contact angle, sliding angle, and soil release property were investigated. The results show that PFPE in this study can be utilized as an anti-smudge coating material because it shows lower sliding angle and better soil release property than commercial products.

• Journal of the Korean Institute of Gas
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• v.15 no.2
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• pp.69-74
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• 2011

As a way to propose a method for the establishment of practical damage-minimizing plan for chemical plants, the release scenario was established by using API-581 BRD and the effect zone was estimated by the KS-RBI program supporting the quantitative cause analysis. And the risk assessment was performed. As a result, we found that to minimize the damage of a chemical plant, it is effective to use four release hole diameters (small, medium, large and rupture) and release time estimated according to the classes of detection and isolation systems. In addition, it can be safely said that through appling the damage areas considering weighted average by failure frequency and worst-case simultaneously, industrial sites can come up with the effective emergency response plan.

• Korean Journal of Organic Agriculture
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• v.4 no.2
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• pp.86-96
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• 1995

This experiment was carried out to investigate the effect of slow-release fertilizers on yield of chinese cabbage and spinach. Fertilizers were treated with CDU, MEISTER, Jobi Gohyungbokhapbiryo, Kyungki Wonyebokbi 1ho, kyungkibokbi Nojeok, Kyungki Jeonjakgohyungbokbi, Traditional manuring, and No manuring. Yields of chinese cabbage were increased with slow-release fertilizers, and CDU was more effective to the head than to the out-leaf, especially. Spinach was increased with slow-release fertilizers, also. However, analysis of chemical components of plants and soil were no difference. It was very effective to increase yields of chinese cabbage and spinach, to reduce in number of supplementary manuring and laboring.

• Journal of Pharmaceutical Investigation
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• v.38 no.6
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• pp.387-392
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• 2008

Alfuzosin, an Alphal-adrenoceptor antagonist is used for the treatment of patients with voiding and in a lesser extent storage lower urinary tract symptoms (LUTS) associated to benign prostatic hyperplasia (BPH). The objective of this study was to formulate sustained release alfuzosin HCl granules and assess their formulation variables. The $Eudragit^{(R)}$ as a polymer, sustained release membrane, and dibutyl sebacate (DBS) as a plasticizer were used. Multi-coated alfuzosin HCl delivery systems composed of sugar sphere, various excipients, $Eudragit^{(R)}$ and HPMC (hydroxy propyl methyl cellulose), Cellulose Acetate were prepared by fluid-bed coater. Membrane layer were used $Eudragit^{(R)}$ RS PO and NE 30D. And the alfuzosin HCl coated beads were coated immediate release drug layer for initial burst. Its dissolution test was carried out compared to conventional products ($XATRAL^{(R)}$ XL). The release rate of drug from coated beads was higher than that from $XATRAL^{(R)}$ XL in pH 6.8.

• Bulletin of the Korean Chemical Society
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• v.32 no.3
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• pp.867-872
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• 2011

For the prolonged delivery and sustained release rates of low molecular weight drugs, poly(lactic-co-glycolic acid) (PLGA) microparticles containing the drug SKL-2020 have been investigated. On increasing polyvinyl alcohol (PVA) concentration (from 0.2% to 5%), the size of microparticles decreased (from $48.02{\mu}m$ to $10.63{\mu}m$) and more uniform size distribution was noticeable due to the powerful emulsifying ability of PVA. A higher drug loading (from 5% to 20%) caused a larger concentration gradient between 2 phases at the polymer precipitation step; this resulted in decreased encapsulation efficiency (from 34.19% to 25.67%) and a greater initial burst (from 61.71% to 70.05%). SKL-2020-loaded PLGA microparticles prepared with different fabrication conditions exhibited unique release patterns of SKL-2020. High PVA concentration and high drug loading led to an initial burst effect by rapid drug diffusion through the polymer matrix. Since PLGA microparticles enabled the slow release of SKL-2020 over 1 week in vitro and in vivo, more convenient and comfortable treatment could be facilitated with less frequent administration. It is feasible to design a release profile by mixing microparticles that were prepared with different fabrication conditions. By this method, the initial burst could be repressed properly and drug release rate could decrease.

• Polymer(Korea)
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• v.29 no.3
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• pp.282-287
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• 2005

A novel ice particle leaching method for fabrication of porous and biodegradable PLGA scaffold has been proposed for the application to tissue engineering. After uniform mixing of poly(L-lactide-co-glycolide) (PLGA) and bovine serum albumin-fluorescein isothiocyanate (FITC-BSA), the FITC-BSA loaded scaffold was fabricated by adding various ratio of ice particle. The release profiles of FITC-BSA were examined using pH 7.4 PBS for 28 days at $37^{circ}$. The release amount was determined by fluorescence intensity by using the fluorescence spectrophotometer and the morphological change of the scaffolds was observed by scanning electron microscope. The release initial burst of BSA containing scaffolds was lower than that of simple dipping scaffolds resulting in constant release aspect. Although the BSA concentration increased. the initial burst was not increased. As a result of this study, it can be suggested that ice particle leaching method for the tissue engineered scaffold miff be very useful and it is possible to impregnate with water soluble factors like cytokine. We suggest that ice particle leaching method may be useful to tissue engineered organ regeneration.

• YAKHAK HOEJI
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• v.37 no.5
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• pp.511-519
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• 1993

The short and variabke transit of drug throught GI tracj and the inter-and intra-subject variations of the transit restrict the sustained drug absorption after oral adminstration. These restrictions may be solved by retaining the dosage forms in the stomach. Then the dosage form will act as a platform which releases the drug slowly and makes the GI absorption occur for a long time. In this study, as the platforms, PVP hydrogels were synthesized by chemical and y-irradiation method in the cylindrical test tube. The chemical method means the synthesis of the hydrogel by heating the mixed solution of N-vinyl-2-pyrrolidone [monomer], acrylated albumin [crosslinking agent], 2, 2'-agobis(2-methylpropionitrile) [initiator] and proxyphylline [drug] at $65^{\circ}C$ for 5 hr. The $\gamma$-irradiation method means the synthesis of the hydrogel by irradiation with $^{60}$ Co $\gamma$-ray of the mixed solution of the monomer, acrylated albumin, and flurbiprofen [drug] at room temperature with total 0.2 Mrad for 3 hr. Our intention is to design the hydrogel tablet (diameter : 1.20 cm, thickness : 0.60 cm) which swells in the gastric fluid after oral administration to such a size that passing through the pylorus could be inhibited during the period of drug release. After releasing drug, the hydrogel should be degraded by the enzymeatic digestion in the stomach, or by hydrolysis and eventually solubilized. Thus, in votro tests were performed to examine the factors that affect swelling and drug release from the PVP hydrogels. Experimental results show that the hydrogels swell to a size larger than the diameter of the pylorus(l.3$\pm$0.7 cm) and the hydrogel prepared by the chemical method is digested by pepsin. But the hydrogel prepared by the $\gamma$-irradiation method was not digested by the pepsin and just collapsed with time. Thus, the swelling of the hydrogel synthesized by $\gamma$-irradiation was independent albumin acrylation time and pepsin concentration. But drug content and radiation dose affected the swelling and drug release kinetics of the hydrogel. Drug release from the hydrigels was prolonged up to about 24 hr. Therefore, it was concluded that by adjusting these factors, the albumin-crosslinked PVP hydrogel synthesized by $\gamma$-irradiation method is expected to be retained in the stomach for up to 60hr and be a potential platform of drugs for long-term GI absorption.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1893-1895
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• 2001

In this paper, novel release technique using wet etch is proposed. The results of this technique and the results of SAMs (Self-Assembled monolayers) coated after release using this technique are compared. Fabricated structure have 100 um in width and experimental length is from 100 um to 1 mm. Thickness of aluminum sacrificial layer is 2 um and structure thickness is 2.5 um. Cantilevers and bridges are fabricated with electroplated gold and silicon nitride deposited on substrate. An aluminium sacrificial layer was evaporated thermally and removed in various wet etching solutions. Detachment length of cantilever is 200 um and detachment length of bridge is 1 mm after isooctane rinsing. And the SAMs coating condition which is appropriate for gold and nitride are studied respectively.

• Korean Journal of Microbiology
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• v.39 no.1
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• pp.8-15
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• 2003

To evaluate the effects of slow release fertilizer and chemical dispersant on oil biodegradation, mesocosm studies were conducted on sand seashore. The rapid removal rates (85%) of aliphatic hydrocarbons and the simultaneous decreases of n-$C_{17}$/pristane (69%) and $n-C_{18}/phytane$ (61%) ratios by the addition of slow-release fertilizer (SRF) within 37 days of experiment indicated that SRF could enhance the oil degrading activity of indigenous microorganisms in sand mesocosm. Although the growth of heterotrophic bacteria and petroleumdegrading bacteria in the mesocosm treated with $Corexit 9527^{R}$ was stimulated, the biological oil removal based on the ratios of $Corexit 9527^{R}$ and $n-C_{18}/phytane$ was inhibited. Removal rates of aliphatic hydrocarbons (56%), and n-$C_{17}$/pristane (27%) and $n-C_{18}/phytane$ (17%) ratios by the addition of chemical dispersant $Corexit 9527^{R}$ were similar or lower than those values of control (50, 60, 46%), respectively. The biodegradation activity, however, when simultaneously treated with SRF and $Corexit 9527^{R}$, was not highly inhibited and even recovered after the elimination of chemical dispersant. From these results it could be concluded that the addition of SRF enhanced the oil removal rate in oligotrophic sand seashore and chemical dispersant possibly inhibit the oil biodegradation. Hence, in order to prevent the unrestrained usage of chemical dispersant in natural environments contaminated with oil, the National Contingency Plan of Oil Spill Response should be carefully revised in consideration of the application for bioremedaition techniques.