• Bulletin of the Korean Chemical Society
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• 제23권6호
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• pp.872-879
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• 2002

One of the improtant characteristics of core-shell type nanoparticles is the long-term storage and reuse as an aqueous injection solution when required. For this reason, reconstruction of lyophilized core-shell type nanoparticles is considered to be essential . BAB type triblock copolymers differ from AB type diblock copolymers, which contain the A block as a hydrophilic part and the B block as a hydrophobic part. by not being easily redistributed into phosphate-buffered saline (PBS, pH 7.4, 0.1 M). Therefore, lyophilized core-shell type nanoparticles of CEC triblock copolymer were reconstituted using a somication process with a bar-type sonicator in combination with a freezing-thawing process. Soncation for 30s only resuspended CEC nanoparticles in PBS; their particle size distribution showed a monomodal pattern with narrow size distribution. The bimodal size distribution pattern and the aggregates were reduced by further sonication for 120 s but these nanoparticles showed a wide size distribution. The initial burst of drug release was increased by reconstitution process. The reconstitution of CEC core-shell type nanoparticles by freezing-thawing resulted in trimodal distribution pattern and formed aggregates, although freezing-thawing process was easier than sonication . Drug release form CEC nanoparticles prepared by freezing-thawing was slower than from the original dialysis solution. Although core-shell typenanoparticles of CEC triblock copolymers were not easily performed. Cytotoxicity testing of core-shell type nanoparticles of CEC-2 triblock copolymers containing clonazepam (CNZ) was performed using L929 cells. Cytotoxicity of CNZ was decreased by incorporation into nanoparticles.

• Bulletin of the Korean Chemical Society
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• 제22권5호
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• pp.467-475
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• 2001

A triblock copolymer based on $poly(\varepsilon-caprolactone)$ (PCL) as the hydrophobic part and poly(ethylene glycol) (PEG) as the hydrophilic portion was synthesized by a ring-opening mechanism of ${\varepsilon}-caprolactone$ with PEG containing a hydroxyl group at bot h ends as an initiator. The synthesized block copolymers of PCL/PEG/PCL (CEC) were confirmed and characterized using various analysis equipment such as 1H NMR, DSC, FT-IR, and WAXD. Core-shell type nanoparticles of CEC triblock copolymers were prepared using a dialysis technique to estimate their potential as a colloidal drug carrier using a hydrophobic drug. From the results of particle size analysis and transmission electron microscopy, the particle size of CEC core-shell type nanoparticles was determined to be about 20-60 nm with a spherical shape. Since CEC block copolymer nanoparticles have a core-shell type micellar structure and small particle size similar to polymeric micelles, CEC block copolymer can self-associate at certain concentrations and the critical association concentration (CAC) was able to be determined by fluorescence probe techniques. The CAC values of the CEC block copolymers were dependent on the PCL block length. In addition, drug loading contents were dependent on the PCL block length: the larger the PCL block length, the higher the drug loading content. Drug release from CEC core-shell type nanoparticles showed an initial burst release for the first 12 hrs followed by pseudo-zero order release kinetics for 2 or 3 days. CEC-2 block copolymer core-shell type nanoparticles were degraded very slowly, suggesting that the drug release kinetics were governed by a diffusion mechanism rather than a degradation mechanism irrelevant to the CEC block copolymer composition.

• 한국재료학회지
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• 제22권6호
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• pp.298-302
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• 2012

Fe/$SiO_2$ core-shell type composite nanoparticles have been synthesized using a reverse micelle process combined with metal alkoxide hydrolysis and condensation. Nano-sized $SiO_2$ composite particles with a core-shell structure were prepared by arrested precipitation of Fe clusters in reverse micelles, followed by hydrolysis and condensation of organometallic precursors in micro-emulsion matrices. Microstructural and chemical analyses of Fe/$SiO_2$ core-shell type composite nanoparticles were carried out by TEM and EDS. The size of the particles and the thickness of the coating could be controlled by manipulating the relative rates of the hydrolysis and condensation reaction of TEOS within the micro-emulsion. The water/surfactant molar ratio influenced the Fe particle distribution of the core-shell composite particles, and the distribution of Fe particles was broadened as R increased. The particle size of Fe increased linearly with increasing $FeNO_3$ solution concentration. The average size of the cluster was found to depend on the micelle size, the nature of the solvent, and the concentration of the reagent. The average size of synthesized Fe/$SiO_2$ core-shell type composite nanoparticles was in a range of 10-30 nm and Fe particles were 1.5-7 nm in size. The effects of synthesis parameters, such as the molar ratio of water to TEOS and the molar ratio of water to surfactant, are discussed.

• Archives of Pharmacal Research
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• 제29권8호
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• pp.712-719
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• 2006

In this study, we prepared core-shell type nanoparticles of a poly(DL-lactide-co-glycolide) (PLGA) grafted-dextran (DexLG) copolymer with varying graft ratio of PLGA. The synthesis of the DexLG copolymer was confirmed by $^1H$ nuclear magnetic resonance (NMR) spectroscopy. The DexLG copolymer was able to form nanoparticles in water by self-aggregating process, and their particle size was around $50\;nm{\sim}300\;nm$ according to the graft ratio of PLGA. Morphological observations using a transmission electron microscope (TEM) showed that the nanoparticles of the DexLG copolymer have uniformly spherical shapes. From fluorescence probe study using pyrene as a hydrophobic probe, critical association concentration (CAC) values determined from the fluorescence excitation spectra were increased as increase of DS of PLGA. $^1H-NMR$ spectroscopy using $D_2O$ and DMSO approved that DexLG nanoparticles have core-shell structure, i.e. hydrophobic block PLGA consisted inner-core as a drug-incorporating domain and dextran consisted as a hydrated outershell. Drug release rate from DexLG nano-particles became faster in the presence of dextranase in spite of the release rate not being significantly changed at high graft ratio of PLGA. Core-shell type nanoparticles of DexLG copolymer can be used as a colonic drug carrier. In conclusion, size, morphology, and molecular structure of DexLG nanoparticles are available to consider as an oral drug targeting nanoparticles.

• Korean Chemical Engineering Research
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• 제48권1호
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• pp.98-102
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• 2010

목련잎 추출액을 이용하여 Au core-Ag shell 합금 나노입자를 합성하였다. 환원제인 식물잎 추출액을 먼저 $HAuCl_4$ 용액과 반응시키고 다음에 $AgNO_3$ 용액과 반응시켜 금 seed와 은 shell을 형성시켰다. 반응시간에 따른 UV-visible spectroscopy의 변화를 모니터링하여 합금 나노입자의 형성을 관찰하였다. 합성된 합금 나노입자를 transmission electron microscopy(TEM), energy dispersive X-ray spectroscopy(EDS), X-ray photoelectron spectroscopy(XPS) 등으로 특성화 하였다. TEM image로부터 관찰된 합금 나노입자는 삼각형, 오각형, 육각형 등의 평판과 구 구조의 혼합물이었다. EDS와 XPS 분석으로부터 결정된 금/은 합금 나노입자의 원자 은 함량은 각각 34와 65 wt%로 Au core-Ag shell 나노구조가 형성되었음을 알 수 있었다. 이러한 core-shell 형태의 나노구조는 표면 강화 라만 분광 및 생물분자의 고감도 검출 등에 잠재적인 응용이 기대된다.

• Archives of Pharmacal Research
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• 제20권4호
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• pp.324-329
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• 1997

AB-type amphiphilic copolymers (abbreviated as LE) composed of poly (L-leucine) (PLL) as the A component and poly (ethylene oxide) (PEO) as the B component were synthesized by the ring-opening polymerization of L-leucine N-carboxy-anhydride initiated by methoxy polyoxyethylene amine $(Me-PEO-NH_2)$ and characterized. Core-shell type nanoparticles were prepared by the diafiltration method. Particle size distribution obtained by dynamic light scattering was dependent on PLL composition and the size for LE-1, LE-2 and LE-3 was $369.6{\pm}267$, $523.4{\pm}410$ and $561.2{\pm}364 nm$, respectively. Shapes of the nanoparticies observed by transmission electron microscope (TEM) were almostly spherical. The critical micelle concentration (CMC) of the nanoparticles determined by a fluorescence probe technique was dependent on the composition of hydrophobic PLL, and the CMC for LE-1, LE-2 and LE-3 was $2.0{\times}10^{-6},1.7{\times}10^{-6}$ and $1.5{\times}10^{-6}(mol/l) $, respectively. Clonazepam release from core-shell type nanoparticles in vitro was dependent on PLL composition and drug loading content.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권2호
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• pp.1551-1554
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• 2007

To overcome defect due to large surface of nanoparticle, a redispersible Eu doped $LnPO_4:LnPO_4$ core/shell nanoparticles were prepared in a highboiling coordinating solvent. The particle size of the synthesized core/shell nanophosphors was estimated to be about 8 nm by TEM. In this core/shell nanoparticle, the concentration of Eu ion was optimized on the basis of the emission intensity under UV ray excitation. Also, the PL properties of the nanophosphors have been compared with those of the $LnPO_4:Eu$ nanoparticles.

• 세라미스트
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• 제21권3호
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• pp.283-292
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• 2018

Here, we introduce various type of inorganic nanostructure synthesized with functional nanoparticles and silica. From two decades ago, functional inorganic nanoparticles have been synthesized and highlighted, now we moved to next level of wet-chemical synthesis. By integrating functional nanoparticles with silica, we were able to synthesize multi-functional nanostructure, which expand the applications of nanoparticles to catalyst, drug carrier, sensors. In this context, silica has been spotlighted due to its versatility. Silica has highly biocompatible, relatively transparent and stable under harsh conditions. Thus it can be used as good supporter to synthesize complex multi-functional nanostructure when mixed with other functional nanoparticles. A various shape of complex nanostructures have been synthesized including core-shell type, yolk-shell type and janus type etc. In this paper, we have described the purposes of synthesizing silica noncomplex and various case studies for biomedical applications and self-assembly.

• Bulletin of the Korean Chemical Society
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• 제32권4호
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• pp.1277-1281
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• 2011

Making use of chitosan (CS) and ethylenediaminetetraacetic acid (EDTA) as a reaction system, CS-EDTA nanoparticles were synthesized through a facile counterion complex coacervation method. $Ag^+$ could enter porous CS nanoparticles synthesized with this method, allowing Ag nanoparticles within chitosan nanoparticles were synthesized by reducing silver nitrate with chitosan. Because of the noncovalent interaction between CS and EDTA, the EDTA could be easily removed via dialysis against water, and pure core/shell-type Ag/CS nanoparticles could be obtained. The nanoparticles showed higher antibacterial activity toward E. coli than the active precursor Ag nanoparticles and CS.

• 폴리머
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• 제38권1호
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• pp.80-84
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• 2014

가교결합된 코어와 PBA, PS 더블-셸을 갖는 고분자 나노입자를 제조하고 압력가소 특성을 평가하였다. 더블-셸을 합성하기 위해 먼저, 가교된 코어입자를 St, DVB의 에멀션 중합을 통해서 제조하였으며, 이어서 PBA가 내부셸, PS가 외부셸을 형성하도록 3 단계의 연속적인 에멀션 중합을 수행하였다. 제조된 더블-셸 나노입자는 가교된 코어의 존재에도 불구하고 PBA, PS 간 압력상용성을 발견할 수 있었으며, $25^{\circ}C$에서 반투명한 시편으로 압출성형될 수 있었다. 기계적 물성측정 결과, 성형물의 탄성계수는 더블-셸 나노입자의 크기에 직접적으로 연관됨을 알 수 있었다. 또한 PBA가 과량으로 첨가된 시편의 경우, $25^{\circ}C$에서 재가공이 성공적으로 진행되어 5회의 연속된 압출성형에도 불구하고 0.55MPa의 탄성계수와 1.81 MPa의 파단강도를 얻을 수 있었다.