• Journal of Pharmaceutical Investigation
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• v.32 no.4
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• pp.327-330
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• 2002

Alginate based polymeric matrices were designed for controlled release and stabilization of cefaclor in gastrointestinal fluid. Cefaclor is known to be acid stable and subjected to be degraded at neutral and alkaline pHs. In order to achieve an effective release profile of cefaclor in gastrointestinal tract, a particular strategy in dosage form design should be required from the view point of maintaining its activity. The amphiphilic nature of cefaclor allowed its controlled release using ionic polymers based on ionic interaction between the drug and polymers. The thrust of this study was to develop a technique that delivers cefaclor keeping effective release rate in the intestinal tract. Considering the fast degradation of cefaclor in the intestinal fluid, the matrices were designed to release surplus amount of cefaclor. The alginate based matrices demonstrated increase in release rate in the simulated intestinal fluid, which was favorable to compensate the degraded portion of cefaclor. In addition, stabilization of cefaclor in the intestinal fluid was obtained by employing citric acid that provides an local acidic environment. The matrices might be valuably used for the development of an oral cefaclor dosage form.

• YAKHAK HOEJI
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• v.38 no.6
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• pp.637-645
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• 1994

The effect of various drugs on the stability of the liposomal membrane of phosphatidylcholine and cholesterol was studied, employing the fluorescence self-quenching method. Calcein was entrapped into the phospholipid small unilamellar vesicles and the leakage of the fluorescence probe was monitored on adding the drug to the system. The results of the experiments showed that phenothiazine derivatives, some potent local anesthetics and surface active agents were very effective in inducing the leakage of calcein from the liposome. The leakage-inducing activity of these drug substances has been ascribed to their surface activity and the perturbation of the liposomal membrane by these substances. On the other hand drug substance with low surface activity or without amphiphilic moieties did not show any effect or only small effect on the leakage of calcein from the liposomes. The effect of lipid concentration on the stability of the liposomes was also investigated to show that the higher concentrations of lipid more drug was required to induce the leakage. The effect of surface charges of vesicles was also studied, and the results showed that the charge on the liposomes enhanced the stability of the liposomes against the leakage-inducing activity of these drug substances.

• Bulletin of the Korean Chemical Society
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• v.31 no.8
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• pp.2223-2227
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• 2010

Reaction of [(bpy)Pd]$(PF_6)_2$ (bpy = 2,2'-bipyridine) with racemic bis(isonicotinoyl)-1,1'-bi-2-naphtholate (L) in acetone, and followed by addition of chloroform and solvent evaporation allows to form amorphous micro-bowl morphology consisting of $[(bpy)PdL]_2(PF_6)_4$ without any template or additive. In contrast, the reaction and recrystallization in acetone for 1 week produce parallel-piped single crystals consisting of $[(bpy)_3Pd_3({\mu}_3-HPO_4)_2](PF_6)_2$. The formations of micro-bowl and parallel-piped single crystal morphologies appear to be primarily associated with the kinetic and thermodynamic control, respectively. The formation of micro-bowls may be attributed to eruption of organic solvents. Cosolvent effects and chemical properties on the formation of micro-bowl morphology have been observed.

• Bulletin of the Korean Chemical Society
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• v.34 no.3
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• pp.931-935
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• 2013

Lipid events in liposome-mediated transfection (lipofection) are largely unknown. Here we studied whether phospholipase D (PLD), an important enzyme responsible for phospholipid breakdown, was affected during lipofection of HepG2 cells with a luciferase plasmid. Synthetic cholesterol (Chol) derivatives, including $3{\beta}$[L-ornithinamide-carbamoyl]Chol, [polyamidoamine-carbamoyl]Chol and $3{\beta}$[N-(N',N'-dimethylaminoethane)-carbamoyl]Chol, and a cationic lipid, N-[1-(2,3-dioleyloxy)propyl]-N,N,N-trimethylammonium chloride were mixed with a helper lipid dioleoylphosphatidylethanolamine to form respective cationic liposomes. All cationic liposomes were found to stimulate PLD. Although orders of magnitude effects of the cationic liposomes on PLD stimulation did not consistently match those on cytotoxicity and luciferase expression, a causal relationship between PLD activation and cytotoxic effect was remarkable. PLD stimulation by the cationic liposomes was likely due to their amphiphilic characters, leading to membrane perturbation, as supported by similar results obtained with other membrane-perturbing chemicals such as oleate, melittin, and digitonin. Our results suggest that lipofection induces cellular lipid changes such as a PLD-driven phospholipid turnover.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.882-885
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• 2004

Organic molecules have many properties that make them attractive for electronic applications. We have been examining the progress of memory cell by using molecular-scale switch to give an example of the application using both nanoscale components and Si-technology. In this study, molecular electronic devices were fabricated with amion style derivatives as redox-active component to compare to the devices using Zn-Porphyrin derivatives. This molecule is amphiphilic to allow monolayer formation by the Langmuir-Blodgett (LB) method, and then this LB monolayer is inserted between two metal electrodes. According to current-voltage (I-V) characteristics, it was found that the devices show remarkable hysteresis behavior and can be used as memory devices at ambient conditions, when aluminum oxide layer was existed on bottom electrode. Diode-like characteristics were measured only, when Pt layer was existed as bottom electrode. It was also found that this metal layer interacts with the organic molecules and acts as a protecting layer, when thin Ti layer was inserted between the organic molecular layer and the top Al electrode. These electrical properties of the devices may be applicable to active components for the memory and/or logic gates in the future.

• Bulletin of the Korean Chemical Society
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• v.32 no.7
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• pp.2187-2192
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• 2011

Hydrogen peroxide plays a key role as a second messenger in the normal cellular signaling but its overproduction has been implicated in various life-threatening diseases. Peroxalate chemiluminescence is the light emission from a three component reaction between peroxalate, hydrogen peroxide and fluorophores. It has proven great potential as a methodology to detect hydrogen peroxide in physiological environments because of its excellent sensitivity and specificity to hydrogen peroxide. We developed chemiluminescent micelles composed of amphiphilic polymers, peroxalate and fluorescent dyes to detect hydrogen peroxide at physiological concentrations. In this work, we studied the relationship between the chemiluminescence reactivity and stability of peroxalate by varying the substitutes on the aryl rings of peroxalate. Alkyl substitutes on the aryl ring of peroxalate increased the stability against water hydrolysis, but diminished the reactivity to hydrogen peroxide. Chemiluminescent micelles encapsulating diphenyl peroxalate showed significantly higher chemiluminescence intensity than the counterpart encapsulating dimethylphenyl or dipropylphenyl peroxalate. Diphenyl peroxalate-encapsulated micelles could detect hydrogen peroxide generated from macrophage cells stimulated by lipopolysaccharide (LPS) and image hydrogen peroxide generated during LPS-induced inflammatory responses in a mouse.

• YAKHAK HOEJI
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• v.35 no.1
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• pp.45-60
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• 1991

lonophores, uniquely, create specific pathways of ion permeability in model and cell membranes. Calcium-transporting ionophores of microbiological origin, such as A23187 and ionomycin, have been used as experimental tools to elucidate the physiological role of calcium as a second messenger in many cell types. These ionophores are believed to bypass the initial ligand-receptor step in the activation of cells by increasing membrane permeability to calcium. In this report, we shall discuss several naturally occurring substances that share some properties of calcium-ionophores, primarily concentrating on oxidized fatty acids. We have previously demonstrated that oxidized linoteic and arachidonic acids, obtained either by lipoxygenase catalysis or nonenzymatic processes, significantly promote calcium translocation in a two-phase partition model and modulate calcium-transporting function in the isolated sarcoplasmic reticulum vesicles obtained from mammalian hearts. We have also confirmed that calcium-ionophoric properties are due not to their general amphiphilic nature of certain lipids, but to distinct structural characteristics. Although there are some skeptical views on the occurrence of ionophores in higher organisms, increasing evidence suggests that membrane lipids or their derivatives may serve as physiological calcium-ionophores. Abnormal accumulation of lipid peroxidation products(particularly end products), however, may be associated with the general oxidative damages as seen in many pathological conditions.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.7
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• pp.287-291
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• 2002

We fabricated the crosslinked films using p-hexadecoxyphenol (p-HP), which is amphiphilic and can form polyion complexes with formaldehyde at the air-water interface. The behavior of polyion complexation at the air-water interface and the surface structure of LB films was investigated by Brewster angle microscope(BAM) and scanning Maxwell-stress microscope (SMM), respectively. Also, the electrical properties for crosslinking in phenol-formaldehyde LB films were investigated by measuring conductivity and dielectric constant. The conductivities of p-HP LB films are as follows: heat-treatment of 1% formaldehyde subphase(3.76$\times$10$^{-15}$ ~4.76$\times$10$^{-1}$5[S/cm])$\times$10$^{-14}$ ~1.74$\times$10$^{-14}$ [S/cm]). Also, relative dielectric constants of p-HP LB films were reduced from 6.76~7.84 (pure water) to 2.97~3.25 (heat-treatment of 1% formaldehyde subphase))

• Macromolecular Research
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• v.14 no.1
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• pp.52-58
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• 2006

A novel fabrication of the patterned surfaces in the polymer films was demonstrated by using the self-organizing character of the block copolymers of polystyrene-b-oligothiophenes and polystyrene-b-aromatic amide dendron. Hexagonally arranged open pores with a micrometer-size were spontaneously formed by casting the polymer solutions under a moist air flow. The amphiphilic character of the block copolymers played the crucial role as a surfactant to stabilize the inverse emulsion of water in the organic solvent, and subsequently the aggregated structure of the hydrophilic oligothiophene or aromatic amide dendron segments remained on the interiors of the micropores. The chemical composition on the top of the surface of the microporous films was characterized by energy-filtering transmission electron microscopy (EFTEM) or a time-of-flight secondary ion mass spectrometer (ToF-SIMS). The characterizations clearly indicated that the patterned surfaces in the self-organized block copolymer films with the hexagonally ordered microporous structures were fabricated in a single step.

• Macromolecular Research
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• v.15 no.7
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• pp.646-655
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• 2007

To achieve targeted drug delivery for chemotherapy, a ligand-mediated nanoparticulate drug carrier was designed, which could identity a specific receptor on the surfaces of tumor cells. Biodegradable poly(ethylene oxide)/poly$({\varepsilon}-caprolactone)$ (PEG/PCL) amphiphilic block copolymers coupled to biotin ligands were synthesized with a variety of PEG/PCL compositions. Block copolymeric nanoparticles harboring the anticancer drug paclitaxel were prepared via micelle formation in aqueous solution. The size of the biotin-conjugated PEG/PCL nanoparticles was determined by light scattering measurements to be 88-118 nm, depending on the molecular weight of the block copolymer, and remained less than 120 nm even after paclitaxel loading. From an in vitro release study, biotin-conjugated PEG/PCL nanoparticles containing paclitaxel evidenced sustained release profiles of the drug with no initial burst effect. The biotin-conjugated PEG/PCL block copolymer itself evidenced no significant adverse effects on cell viability at $0.005-1.0{\mu}g/mL$ of nanoparticle suspension regardless of cell type (normal human fibroblasts and HeLa cells). However, biotin-conjugated PEG/PCL harboring paclitaxel evidenced a much higher cytotoxicity for cancer cells than was observed in the PEG/PCL nanoparticles without the biotin group. These results showed that the biotin-conjugated nanoparticles could improve the selective delivery of paclitaxel into cancer cells via interactions with over-expressed biotin receptors on the surfaces of cancer cells.