• Polymer(Korea)
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• v.28 no.1
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• pp.59-66
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• 2004

Thermosensitive poly(N-isopropylacrylamide) gels containing temperature-sensitive liposomes showing temperature-dependent sol-gel transition were prepared. The surface of temperature-sensitive liposome was modified with copolymers of N-isopropylacrylamide and octadecylacrylate, which exhibited a lower critical solution temperature at around 30 $^{\circ}C$ After mixing the modified temperature-sensitive liposomes with poly(N-isopropylacrylamide) solution, the temperature-sensitive 1iposomes formed physically cross-linked gels through heating the solution above their lower critical solution temperatures. The release of drug from temperature-sensitive liposomes was determined by measuring fluorescence intensity. The drug release from temperature-sensitive liposomes in poly(N-isopropylacrylamide) gel gradually showed sustained-release with increasing temperature.

• Journal of the Korean Chemical Society
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• v.47 no.3
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• pp.257-264
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• 2003

This study has investigated the temperature-sensitive liposomes, which release anticancer drug(doxorubicin) at the hyperthermia temperature$(~40^{\circ}C)$. The temperature-sensitive liposomes were modified with a copolymers of N-isopropylacrylamide(NIPAAm) and acrylamide(AAm), which exhibit a lower critical solution temperature (LCST) at the hyperthermia temperature. The release of doxorubicin from the modified liposomes was determined by measuring the fluorescence intensity with changing temperature and time. The release of doxorubicin from liposomes modified with poly(NIPAAm-co-AAm) copolymer was increased significantly, because poly(NIPAAm-co-AAm) could undergo the conformational transition in the narrow hyperthermia temperature region$(~40{\pm}2^{\circ}C)$. Moreover, we observed that doxorubicin released from liposomes within 5 minutes, and the size of modified liposomes was 120~170 nm. In this study, we have prepared temperature-sensitive liposomes which could be controlled by temperature. They can be applied in the field of a drug delivery system for tumor targeting by temperature control.

• Journal of the Korean Chemical Society
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• v.58 no.6
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• pp.575-579
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• 2014

Development of liposomes has been actively studied for effective delivery of drug at tumor site. However, despite their preferential accumulation at tumor site, the therapeutic efficacy of such liposomal drug has been limited because of low drug release. Therefore, we developed a temperature-sensitive liposome (TSL), which can be made to maximize release of drug by external stimulation such as ultrasound. Doxorubicin (DOX) as a model drug was encapsulated into TSL by a pH gradient method. The particle size of the TSL was $142.0{\pm}6.24nm$. Surface charge was $-10.55{\pm}1.12mV$. Release of drug from TSLs was up to 80% within 15 min at over $42^{\circ}C$ measured by fluorescence intensity. Cytotoxicity of released DOX from TSLs with ultrasound was highly increased compared to TSLs without ultrasound. Taken together, we demonstrate that temperature sensitive drug release from TSLs with ultrasound, which may be useful for cancer therapy to increase drug concentration at tumor site by external stimulation.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2019.04a
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• pp.82-82
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• 2019

종자은행은 종자를 보존하는 가장 경제적이고 효율적인 보전방법이지만, 수종에 따라 저장특성의 차이가 커서 수종별 저장방법의 확립이 필요하다. 초저온저장 방법은 세포 분열, 대사 작용을 정지 상태로 유지하므로 현재까지 장기간 보존을 위한 비용이 효율적이며 안정적인 방법이다. 공시재료는 멸종위기 야생식물 등 22종을 대상으로 하였다. 액체질소에 7일간 종자를 침지한 후 $37^{\circ}C$ 항온수조에서 10분간 해동하였다. 휴면이 있는 수종은 파종 전 종자를 저온습윤 하였고, 저온습윤 처리 후에도 휴면타파 되지 않는 수종은 농황산, 지베렐린을 개별 또는 혼용으로 처리하였다. 발아 및 유묘 평가는 $25^{\circ}C/20^{\circ}C$(광12h/암12h)조건에서 진행하였으며, 매일 28일차까지 발아조사를 수행한 후 평가하였다. 진달래속의 꼬리진달래와 철쭉이 초저온 민감성을 보였으며, 오리나무속의 물오리나무, 사방오리는 부분 민감성을 보였다. 민산초나무는 지하부건물중이 유의하게 감소한 결과를 보였으며, 이외의 수종은 초저온 민감성을 보이지 않았으므로 장기보존을 위한 초저온 동결보존이 가능한 것으로 보였다.

• Journal of the Korean GEO-environmental Society
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• v.18 no.12
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• pp.37-45
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• 2017

Structural instability and damage are caused by frost heave during the winter when atmospheric temperature maintains below $0^{\circ}C$. Frost heave is the most representative engineering characteristics of frozen ground and there are various frost susceptibility criteria. Frost susceptibility criteria can be roughly divided into three categories. First, frost susceptibility is determined from particle size distribution, which is practically useful and many countries are adopting. In this paper, several particle size distributions (PSDs) are applied to the frost susceptibility criteria but PSD seems to be not enough to determine whether soils are frost susceptible. Second, it is judged from laboratory frost heave testing results. Laboratory frost heave tests were performed with newly developed thermal controlled triaxial cell and the reliability of frost susceptibility criteria is evaluated. New testing apparatus and method are suitable to meet the existing frost susceptibility criteria. Third, it is compositive frost susceptibility criteria envelope including the particle size distribution, soil classification, and frost heave test. The compositive frost susceptibility criteria envelope should be supplemented based on additional data on various soil types.

• 레미콘
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• s.77
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• pp.12-21
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• 2003

• Polymer(Korea)
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• v.35 no.1
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• pp.94-98
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• 2011

Poly(2-hydroxyethyl methacrylate), PHEMA, hybrid gels containing Pluronic and acrylic acid (AAc) were prepared as new biocompatible and stimuli-responsive hydrogels by photo-polymerization technique. The prepared hybrid gel showed reversible, temperature-responsive swelling behavior due to the presence of Pluronic component, which underwent sol-gel transition at an elevated temperature to cause gel shrinkage. The hydrogel also exhibited increased swelling degrees and pH-sensitivity due to the AAc component with ionizable carboxylic acid groups. The microporous gel morphology and its changes upon stimuli was observed by scanning electron microscopy.

• Polymer Science and Technology
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• v.17 no.3
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• pp.312-320
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• 2006

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.562-565
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• 2000

pH- and thermo-sensitive hydrogels containing maleilated chitosan(MC) and N-isopropylacrylamide(NIPAAm) were prepared and characterized for their swelling behavior, biodegradability and drug release profiles. The hydrogels exhibited a typical pH-sensitivity due to the carboxylic acid groups of maleilated chitosan. The change of ratio of NIPAAm to MC in weight did not affect on either lower critical solution temperature(LCST) or EWC significantly. The pH sensitivity of the hydrogel, however, depended on the amounts of carboxylic acid groups of MC. MC was degradable up to 80% weight reduction in 2 hours. The in vitro drug relase profiles were established both in buffer solution pH 1.4 and pH 7.4. Only a negligible amount of indomethacin was released at pH 1.4 in 6 hours, while at pH 7.4 more than 90% of the total drug in the hydrogel was gradually released over ca. 5 hours.

• Proceedings of the Optical Society of Korea Conference
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• 2009.10a
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• pp.80-81
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• 2009