PubMed Health⌕ Search

Biomedical subjects

Jong-Duk Kim

Publications and source records attributed to Jong-Duk Kim.

12 recordsLinked to original sources
PubMed2006

Enhanced diffraction efficiency in a photorefractive liquid crystal cell with poly(9-vinylcarbazole)-infiltrated mesoporous TiO2 layers.

The photorefractive effect of a layer-structured liquid crystal cell was significantly enhanced when a C60-doped poly(9-vinylcarbazole) (PVK)/TiO2 nanocomposite was used in two photoconductive layers. The C60-doped PVK/TiO2 nanocomposite film was prepared by infiltrating C60-doped PVK into a highly ordered mesoporous TiO2 layer. The addition of the TiO2 layer to the C60-doped PVK layer increased the first-order Raman-Nath diffraction efficiency from 24% to 42.9%. This enhancement of diffraction efficiency is attributed to a blocking effect of charge recombination in the composite layer. The electron transfer from the PVK layer into the TiO2 layer would decrease the recombination of photogenerated charges in the PVK layer, while charges in the PVK layer could participate in the formation of a space-charge field.

Journal Article↗
PubMed2006

Histidine-conjugated poly(amino acid) derivatives for the novel endosomolytic delivery carrier of doxorubicin.

Direct conjugation of histidine to poly(2-hydroxyethyl aspartamide) (PHEA-His) and C18-grafted PHEA (PHEA-g-C18-His) was achieved via an ester linkage using N(alpha)-Boc-L-histidine, followed by the deprotection of Boc groups. PHEA-His series would be expected as an endosomolytic synthetic polymer because of the buffering capacity at physiological and endosomal pH regulated by alpha-amine and imidazole groups in side chains. PHEA-g-C18-His series formed stable self-aggregates due to the hydrophobic interaction between grafted alkyl chains. The size, zeta potential, and micropolarity of PHEA-g-C18-His series greatly increased at pH 5.0, because aggregates swelled by a positive surface charge and the electrostatic repulsion of ionized histidine moieties in the aggregate surface. In the confocal microscopy, it was revealed that PHEA-g-C18-His was more uniformly distributed than PHEA-g-C18 in HeLa cells after 8 h of incubation and was attributed to the endosomolytic ability of conjugated histidine moieties. In doxorubicin-loaded self-aggregate systems, the histidine conjugation improved the cell cytotoxicity by a fast release of loaded doxorubicin at low pH and the endosomolytic ability of conjugated histidine, resulting in the easy nuclear access of doxorubicin.

Amines↗
PubMed2005

Bioadhesive interaction and hypoglycemic effect of insulin-loaded lectin-microparticle conjugates in oral insulin delivery system.

Biodegradable microparticles were prepared with alginate by the piezoelectric ejection process, and lectin (wheat germ agglutinin, WGA) was conjugated to alginate microparticles to take advantage of the protective effects of alginate microparticles and the mucoadhesive properties of WGA for improved oral delivery of insulin. Their specific interaction with model mucin was determined by pig mucin (PM) immobilized surface plasmon resonance (SPR) biosensor and in vitro adsorption studies. The hypoglycemic effects of alginate and WGA-conjugated alginate microparticles were examined after oral administration in streptozotocin-induced diabetic rats. The alginate microparticles were fabricated by ejecting alginate/insulin solution into 0.1 M CaCl2 solution through a nozzle actuated by the piezoelectric transducer. The WGA was conjugated to alginate microparticles by activating hydroxyl groups with carbonyldiimidazole (CDI). The affinity constant (K(A)) of alginate-WGA microparticles from the SPR data (K(A)=5.455 g(-1) L) was about nine times greater than alginate microparticles (K(A)=0.628 g(-1) L). In vitro experiments in the mucin solution showed that the conjugated WGA enhanced the interaction about three times. In vivo studies with diabetic rats showed that the blood glucose level of SPF rats was lowest when alginate-WGA microparticles were orally administered. Larger K(A) of alginate-WGA microparticles resulted in larger glucose change (%) from base level. Still, it is not clear whether the transport of insulin through the intestinal mucous membrane was influenced by the increase of residence time at intestinal membrane through the specific adsorption of WGA-conjugated microparticles. However, it is concluded that alginate-WGA microparticles enhance the intestinal absorption of insulin sufficient to drop the glucose level of blood.

Adhesives↗
PubMed2005

Self-aggregates of oligoarginine-conjugated poly(amino acid) derivatives as a carrier for intracellular drug delivery.

N(omega)-2,2,4,6,7-Pentamethyldihydrobenzofuran-5-sulfonyl (N(omega)-Pbf)-protected oligoarginine was directly conjugated to poly(amino acid) derivatives modified with a long alkyl chain. The final concentration of conjugated peptides was easily controlled by the feed ratio of oligoarginine to polymer backbone and a final soluble polymeric system was obtained by the deprotection of N(omega)-Pbf groups. The polymeric conjugates formed stable self-aggregates of size range of 8-40 nm in aqueous solution and effectively internalized into HeLa cells by adsorptive endocytosis.

Drug Delivery Systems↗
PubMed2005

An infantile case of Sturge-Weber syndrome in association with Klippel-Trenaunay-Weber syndrome and phakomatosis pigmentovascularis.

Sturge-Weber syndrome can be associated with facial port-wine stains and intracranial calcification, and concurrent Klippel-Trenaunay-Weber syndrome has been reported. Klippel-Trenaunay-Weber syndrome is a rare congenital mesodermal phakomatosis characterized by cutaneous hemangiomas, venous varicosities and soft tissue or bone hypertrophy of the affected extremities. This report is presented a rare case of the Sturge-Weber syndrome in combination with the Klippel-Trennaunay syndrome and phakomatosis pigmentovascularis in a 4-month-old infant. He showed nevus flameus on the right leg and both part of the face and back, leptomeningeal angiomatosis on right hemisphere, hypertrophy of the right leg, hemiconvulsion on the left and also evidences of congenital glaucoma and nevus of Ota. Very rare case combined with these three kinds of phakomatosis has been reported.

Humans↗
PubMed2004

Monoolein cubic phases containing hydrogen peroxide.

Monoolein (MO) cubic phases were prepared by hydrating MO using distilled water or 12wt.% H(2)O(2) solution so that the content of aqueous phase in the cubic phase is 30wt.%. The thermal transition of the isotropic cubic phase to reversed hexagonal phase was observed on a polarizing photomicroscope and the transition temperature was found to be around 65 degrees C on a differential scanning calorimeter (DSC). Small-angle X-ray scattering (SAXS) patterns indicated the cubic phases had diamond surfaces. The cubic phase released H(2)O(2) into an aqueous phase in a saturation manner so that approx. 50% of total loaded H(2)O(2) release in the first 10 h and thereafter relatively slow was observed over 40 h. The cubic phase was stable at 45 degrees C for 56 days before it broke down into an oily phase and an aqueous phase in 70 days. According to (1)H NMR spectrum, glycerol moiety and -CH(2)=CH(2)- of the oily phase were detected less in number than those of intact MO. Therefore, the hydrolysis and the oxidation of MO would be responsible for the breakdown of the cubic phase. The tensile adhesive forces of the cubic phases were higher than a skin-adhesive patch prepared using polyacrylate. The cubic phase containing H(2)O(2) could be used as a topical disinfected gel for a wounded skin.

Calorimetry, Differential Scanning↗
PubMed2003

Aggregation behaviors and their pH sensitivity of cholesterol-conjugated proteinoids composed of glutamic acid and aspartic acid matrix.

Cholesterol-conjugated proteinoids and their aggregation behaviors were investigated with model proteinoid systems. Model proteinoids of molecular weights in the range of 4000 to 6000 were synthesized by anhydrous thermal condensation forming a matrix with glutamic acid and aspartic acid and of naturally occurring amino acids. Nuclear magnetic resonance and Fourier transform infrared spectra suggested that cholesterol was conjugated to carboxyl group-forming pendants. Native water-soluble proteinoids can form microspheres in acidified or heated conditions, but the cholesterol-conjugated proteinoids were found to form aggregates in water, regardless of the temperature or pH of the solutions. The hydrophobic pendant moieties come to a compact association in core, whereas the hydrophilic chains provide a shield layer.

Aspartic Acid↗
PubMed2003

Polycation gene delivery systems: escape from endosomes to cytosol.

Clinical success of gene therapy based on oligonucleotides (ODNs), ribozymes, RNA and DNA will be greatly dependent on the availability of effective delivery systems. Polycations have gained increasing attention as a non-viral gene delivery vector in the past decades. Significant progress has been made in understanding complex formation between polycations and nucleic acids, entry of the complex into the cells and subsequent entry into the nucleus. Sophisticated molecular architectures of cationic polymers have made the vectors more stable and less susceptible to binding by enzymes or proteins. Incorporation of specific ligands to polycations has resulted in more cell-specific uptake by receptor-mediated mechanisms. However, there are still other barriers limiting the transfection efficiency of polycation gene delivery systems. There is a consensus that polycation-DNA complexes (polyplexes) enter cells via the endocytotic pathway. It is not clearly understood, however, how the polyplexes escape (if they do) from endosomes, how DNA is released from the polyplexes or how the released DNA is expressed. The primary focus of this article is to review various polycation gene delivery systems, which are designed to translocate DNA from endosomes into cytosol. Many polycation gene delivery systems have tried to mimic the mechanisms that viruses use for the endosomal escape. Polycation gene delivery systems are usually coupled with synthetic amphipathic peptides mimicking viral fusogenic peptides, histidine-based gene delivery systems for pH-responsive endosomal escape, polycations with intrinsic endosomolytic activity by the proton sponge mechanism and polyanions to mimic the anionic amphiphilic peptides.

Cytosol↗
PubMed2002

Dynamic surface tension and its diffusional decay of dodecyl ethoxylates with different homologue distribution.

Dynamic surface tension and its diffusional decay have been studied with four different polydisperse C12E7 at different temperatures and different concentrations. The CMC and the headgroup area from equilibrium surface tension were shown with polydispersity and temperature. The chain length of oxyethylene on the surface was derived from comparison between the headgroup area of monodisperse dodecyl ethoxylates and that of polydisperse C12E7. The values for (Deff/D) were deduced with a diffusion-controlled adsorption model using parameters obtained from equilibrium surface tension. It was shown at short adsorption time that molecules were really adsorbed onto the surface in a diffusion-controlled manner. At a comparably long adsorption time, the ratios (Deff/D) were calculated by assuming the selective adsorption onto the surface. The modified Arrhenius-type equation was proposed by putting a concentration term in front of the exponential terms. The modified Arrhenius-type equation gave Ea=30 kJ/mole for this system. Ea directly derived without an Arrhenius plot was between 9 to 11 kJ/mole. It was an indication that the activation energy alone was not enough to explain the decay of dynamic surface tensions.

Alcohols↗
PubMed2002

Self-aggregates of poly(2-hydroxyethyl aspartamide) copolymers loaded with methotrexate by physical and chemical entrapments.

Amphiphilic copolymers based on poly(2-hydroxyethyl aspartamide) (PHEA) formed self-aggregates for the entrapment and release of methotrexate (MTX) by physical entrapment and chemical conjugation. In physical entrapment, MTX was partitioned into hydrophobic domains in self-aggregates of PHEA grafted with octadecyl chains (PHEA-C18) and the amount of the entrapped drug increased linearly by 3.39 mg per the degree of substitution of grafted octadecyl groups. The amphiphilic nature of the drug induced a large initial release in the buffer medium, irrespective of the amount of octadecyl chains. However, PEG-grafted PHEA-C18 copolymers conjugated with MTX, ConG, formed a micelle-like structure by self-association of the conjugates and suppressed the initial large release. The alkyl grafting lowered the CAC, meaning enhancement of aqueous stability. The release was accelerated in pH 10.0 by rapid hydrolysis of ester linkage by base-catalyzed cleavage, while it was significantly reduced at pH 5.0.

Antimetabolites, Antineoplastic↗
PubMed2000

The Dispersion Properties of Precipitated Calcium Carbonate Suspensions Adsorbed with Alkyl Polyglycoside in Aqueous Medium.

The zeta potentials and dispersion properties of precipitated calcium carbonate suspensions adsorbed with alkyl polyglycosides in aqueous medium were investigated. Within the investigated pH ranges, the adsorption curves of alkyl polyglycosides on calcium carbonates show sigmoidal shapes, and the zeta potential decreases as the amount of adsorption increases. At positively charged surfaces of low pH, the adsorption amounts were greater than those at negatively charged surfaces, indicating that alkyl polyglycosides were negatively charged in aqueous solutions. At low concentrations of alkyl polyglycosides, the dispersion stabilities of suspensions were very poor and showed no linearity with zeta potentials over the entire range of pHs, which may be attributed to the onset of hydrophobic interaction between particles due to the adsorption of surfactant molecules. This destabilization continued until monolayer coverage by the surfactant layer was complete. Based on the classical DLVO theory, there may be a strong hydrophobic interaction between particles. Beyond monolayer adsorption, the dispersion stability increases, probably by the formation of hemimicelle or admicelle. Therefore, it is believed that ionization of alkyl polyglycosides and admicelles of surfactants on particle surface plays a key role in the stability of dispersions and the abrupt increase in adsorption. Copyright 2000 Academic Press.

Journal Article↗