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Biomedical subjects

Y I Jeong

Publications and source records attributed to Y I Jeong.

17 recordsLinked to original sources
PubMed2002

Protection against dextran sulfate sodium-induced colitis by microspheres of ellagic acid in rats.

Ellagic acid (EA), a naturally occurring plant phenol, has the antioxidant and anti-inflammatory activities. In the present study, we examined the effect of EA contained in microspheres on the ulcerative colitis induced experimentally in rats by dextran sulfate sodium (DSS). Experimental colitis was induced in male Fisher 344 rats by daily treatment with 3% DSS solution in drinking water for 7 days. EA of microspheres (mcEA: 1 approximately 10 mg/kg as EA contents) was administered p.o. twice daily for 6 days. In a preliminary study, we found that these microsphere capsules, when administered p.o., are effectively dissolved in the proximal to the ileo-cecal junction and distributed to the terminal ileum and the colon. The ulceration area, colon length, and mucosal myeloperoxidase (MPO) activity as well as thiobarbituric acid-reactive substances (TBARS) were measured on 7th day after the onset of DSS treatment. The DSS treatment for 7 days caused severe mucosal lesions in the colon, accompanied with the increases of MPO activity and TBARS as well as the decreases of body weight gain and colon length. Administration of mcEA reduced the severity of DSS-induced colitis in a dose-dependent manner, and a significant effect was observed at 10 mg/kg, the ED50 being 2.3 mg/kg. This mcEA treatment also significantly mitigated changes in various biochemical parameters in the colonic mucosa induced by DSS. Although plain EA (without using microspheres) was also effective in reducing the severity of DSS-induced colitis, this effect was much less potent as compared with that of mcEA; the ED50 was about 15 times higher than that of mcEA. In addition, a significant effect on DSS-induced colitis was also obtained by intra-rectal administration of superoxide dismutase, an anti-oxidative agent. These results suggest that EA prevents the ulcerative colitis induced by DSS, probably by radical scavenging and/or anti-oxidative actions. The microspheres used in this study may be useful for delivering an orally administered drug specifically to the colon.

Animals↗
PubMed2001

Evaluation of an intestinal pressure-controlled colon delivery capsules prepared by a dipping method.

A new method for preparation of large amounts of empty pressure-controlled colon delivery capsules (PCDCs) by a dipping method has been developed. Empty PCDCs are composed of two polymer membranes. The inner one was a water-insoluble polymer membrane, ethylcellulose (EC). The outer one was an enteric polymer membrane, hydroxypropylmethylcellulose phthalate (HPMCP) or hydroxypropylmethylcellulose acetate succinate (HPMCAS). By consequently dipping into an ethanolic EC solution and an alkalized enteric polymer solution, empty PCDCs were obtained after both the capsule body and cap were adjusted to the size of #2 capsules. With each enteric polymer, two types of empty PCDCs of different thickness were prepared. Fluorescein (FL) was formulated with suppository base, PEG1000, and used as a model drug. FL/PEG1000 suspension was introduced into empty PCDCs which were then sealed with enteric polymer solution. The PCDCs were evaluated by an in vivo experiment using beagle dogs. After oral administration of the test PCDC preparations containing 30 mg of FL, blood samples were obtained from the jugular vein and serum FL levels were measured. The thickness of the EC membrane layer varied in both the capsule body and cap. HPMCAS PCDCs had 62.1+/-5.0 (S.E.) microm (body) and 49.7+/-3.3 microm (cap) with thicker ones and 55.7+/-6.6 microm (body) and 46.8+/-6.2 microm (cap) with thinner ones. HPMCP PCDCs had 28.1+/-3.3 microm (body), 30.9+/-1.0 microm (cap) with thinner ones and 43.1+/-9.8 microm (body), 42.4+/-8.2 microm (cap) with thicker ones. The mean T(i) values, the first appearance time, of FL in the serum of HPMCAS PCDCs were 2.0+/-0.7 h for thicker ones and 3.8+/-0.5 h for thinner ones, while the mean T(i) values of HPMCP PCDCs were 2.0+/-0.0 h for thinner ones and 3.5+/-0.7 h for thicker ones. Since the colon arrival time in beagle dogs was 3.5+/-0.3 h as determined by a sulfasalazine test, thinner HPMCAS PCDCs and thicker HPMCP PCDCs were thought to deliver FL to the colon.

Animals↗
PubMed2001

Albumin release from biodegradable hydrogels composed of dextran and poly(ethylene glycol) macromer.

Biodegradable hydrogels based on glycidyl methacrylate dextran (GMD) and dimethacrylate poly(ethylene glycol) (DMP) were proposed for colon-specific drug delivery. GMD was synthesized by coupling of glycidyl methacrylate with dextran in the presence of 4-(N,N-dimethyl-amino)pyridine (DMAP) using dimethylsulfoxide as a solvent. Methacrylate-terminated poly (ethylene glycol) (PEG) macromer was prepared by the reaction of PEG with methacryloyl chloride. GMD/DMP hydrogels were prepared by radical polymerization of phosphate buffer solution (0.1M, pH 7.4) of GMD and DMP, using ammonium peroxydisulfate (APS) and UV as initiating system. The synthetic GMD, DMP, and GMD/DMP hydrogels were characterized by fourier transform infrared (FT-IR) spectroscopy. The FITC-albumin loaded hydrogels were prepared by adding FITC-albumin solution before UV irradiation. Swelling capacity of GMD/DMP hydrogels was controlled not only by molecular weight of dextran, but also by incorporation ratio of DMP Degradation of the hydrogels has been studied in vitro with dextranase. FITC-albumin release from the GMD/DMP hydrogels was affected by molecular weight of dextran and the presence of dextranase in the release medium.

Acrylates↗
PubMed2001

Application of Eudragit P-4135F for the delivery of ellagic acid to the rat lower small intestine.

Based on the assumption that the delivery of ellagic acid to its site of action would show an antiinflammatory activity in inflammatory bowel disease (IBD), we have prepared microspheres using a new pH-sensitive polymer, Eudragit P-4135F (P-4135F), to deliver ellagic acid to the lower small intestine in rats. The microspheres were spherical in shape and the mean diameters were approximately 100-150 microm. The amount of ellagic acid released from the microspheres decreased by increasing the formulated amount of P-4135F. The release characteristics of ellagic acid were pH-dependent. By considering the factors loading efficiency and microsphere particle size distribution, ellagic acid-2 microspheres (P-4135F/ellagic acid = 1.65) were selected for further investigation. In a dissolution study, more than 95% ellagic acid was released within 0.5 h in pH 7.4 and 8.0 buffers. The release percent of ellagic acid was less than 40% in pH 6.8 and 7.0 and was less than 10% in pH 5.6 and 5.9. To observe the dissolution sites of the microspheres in the rat small intestine fluorescein was formulated in the microspheres as a tracer drug along with ellagic acid (50 mg kg(-1)). After intraduodenal administration of fluorescein-labelled microspheres to rats, the plasma fluorescein level started to increase at 0.5 h, by which time the microspheres had reached the middle part of the ileum. Microspheres started to dissolve within 1.0 h and the peak plasma fluorescein concentration was observed at 3.0 h, when the majority of the administered microspheres were dissolved in the terminal ileum. These results suggested that P-4135F microspheres could deliver ellagic acid to the lower part of the small intestine, and that the released ellagic acid would be distributed into the caecum and the ascending colon.

Administration, Oral↗
PubMed2000

Core-shell type polymeric nanoparticles composed of poly(L-lactic acid) and poly(N-isopropylacrylamide).

Poly(L-lactic acid)/poly(N-isopropylacrylamide) (abbreviated as LN) block copolymers were synthesized and the LN nanoparticles were prepared by simple diafiltration method. The thermal transition of the LN nanoparticles was at 32.3 degrees C, the lower critical solution temperature (LCST) of the polymer. The fluorescence spectroscopy data showed that LN was self-assembled in water to form core-shell structure nanoparticles, and the critical association concentration (CAC) value was estimated as 1.3x10(-2) g/l. From the transmission electron microscope observations, the LN nanoparticles were spherically shaped and ranged in size between 30 and 50 nm below the LCST. The hydrated size was measured by photon correlation spectroscopy, and reversible size changes were investigated by the factor of temperature. The release of indomethacin from the LN nanoparticles was thermo-sensitive due to the unique characteristic of poly(N-isopropylacrylamide).

Acrylic Resins↗
PubMed2000

Effect of solvent on the preparation of surfactant-free poly(DL-lactide-co-glycolide) nanoparticles and norfloxacin release characteristics.

The surfactant-free nanoparticles of poly(DL-lactide-co-glycolide) (PLGA) were prepared by dialysis method without surfactant and physicochemical properties such as particle size and drug contents were investigated against used initial solvent. The size of PLGA nanoparticles and drug contents were significantly changed by used initial solvent. The size of PLGA nanoparticles prepared from dimethylacetamide (DMAc), dimethylformamide (DMF), and dimethylsulfoxide (DMSO) as a initial used solvent was smaller than that of acetone. Selected initial solvent used to dissolve the copolymer significantly affects the size of nanoparticles and drug contents. It was shown that PLGA nanoparticles have spherical shapes from the results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. It was thought that surfactant-free nanoparticles of PLGA entrapping norfloxacin (NFX) has nice drug loading capacity without free-drug on the surface of nanoparticles through the analysis of X-ray powder diffraction. From these results, it was showed the potential that the PLGA nanoparticles could be formed successively by dialysis method without surfactant. Release kinetics of NFX used as a model drug was governed by not only drug contents but also particle size parameter. The higher the drug contents and the larger the particle size resulted in slower the drug release.

Anti-Infective Agents↗
PubMed2000

Self-assembled hydrogel nanoparticles composed of dextran and poly(ethylene glycol) macromer.

Biodegradable hydrogel nanoparticles were prepared from glycidyl methacrylate dextran (GMD) and dimethacrylate poly(ethylene glycol) (DMP). GMD was synthesized by coupling of glycidyl methacrylate to dextran in the presence of 4-(N,N-dimethylamino)pyridine (DMAP) using dimethylsulfoxide (DMSO) as an aprotic solvent. DMP was synthesized from poly(ethylene glycol) (PEG) and methacryloyl chloride. GMD/DMP (abbreviated as DP) hydrogel was prepared by radical polymerization of GMD and DMP using ammonium peroxydisulfate (APS) as an initiator and UV curing. DP hydrogel nanoparticles were obtained by diafiltration method using DMSO solution. The GMD and DMP were characterized by fourier transform infrared spectroscopy. Fluorescence probe technique was used to investigate the self-assembly of DP in water using pyrene as a hydrophobic probe. The critical association concentration (CAC) was determined to be 5.6 x 10(-2) g/l. The shape of DP hydrogel nanoparticles was spherical when observed by transmission electron microscope (TEM). The size range of DP hydrogel nanoparticles was about 20 approximately 50 nm. The hydrodynamic size of DP hydrogel nanoparticles was measured by photon correlation spectroscopy (PCS) and gradually increased with time in PBS (0.1 M, pH 7.4). Drug release study was performed using clonazepam (CNZ) as a hydrophobic model drug. In vitro release rate of CNZ from the DP hydrogel nanoparticles was dependent on the existence of dextranase and the pH of the release medium.

Anticonvulsants↗
PubMed2000

Thermo-responsive self-assembled polymeric micelles for drug delivery in vitro.

Cholic acid (CA) was coupled with amine-terminated poly (N-isopropylacrylamide) (ATPNIPAAm) using N,N'-dicyclohexyl carbodiimide as a coupling agent. Self-assembled CA/PNIPAAm conjugate (abbreviated as CN) micelles were prepared by diafiltration method in water. The CN micelles exhibited the lower critical solution temperature (LCST) at 31.5 degrees C. The CN micelles were observed as spherical shapes and their dried sizes were ranged between 30 and 50 nm by the transmission electron microscope (TEM) images. Hydrated micelle sizes measured by photon correlation spectroscopy (PCS) were ranged 337.5+/-67.8 nm. And reversible size changes of CN micelles were observed with two point temperature 10 and 40 degrees C, respectively. From the fluorescence spectra, fluorescence intensity of pyrene in the CN micelles was increased and red-shifted as the concentration of CN increased, indicating the formation of self-assembled polymeric micelles in water. The critical micelle concentration (CMC) was evaluated as 8.9 x 10(-2) g/l. Much more indomethacin (IN) was released from th CN micelles at 10 than at 40 degrees C due to the thermo-sensitivity of the PNIPAAm in the CN polymer.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2000

Clonazepam release from core-shell type nanoparticles of poly(epsilon-caprolactone)/poly(ethylene glycol)/poly(epsilon-caprolactone) triblock copolymers.

The triblock copolymer based on poly(epsilon-caprolactone) (PCL) as hydrophobic part and poly(ethylene glycol) (PEG) as hydrophilic one was synthesized and characterized. Core-shell type nanoparticles of poly(epsilon-caprolactone)/poly(ethylene glycol)/poly(epsilon-caprolactone) (CEC) block copolymer were prepared by a dialysis technique. According to the amphiphilic characters, CEC block copolymer can self-associate at certain concentration and their critical association concentration (CAC) was determined by fluorescence probe technique. CAC value of the CEC-2 block copolymer was evaluated as 0.0030 g/l. CAC values of CEC block copolymer decreased with the increase of PCL chain length, i.e. the shorter the PCL chain length, the higher the CAC values. From the observation of transmission electron microscopy (TEM), the morphologies of CEC-2 core-shell type nanoparticles were spherical shapes. Particle size of CEC-2 nanoparticles was 32.3+/-17.3 nm as a monomodal and narrow distribution. Particle size, drug loading, and drug release rate of CEC-2 nanoparticles were changed by the initial solvents and the molecular weight of CEC. The degradation behavior of CEC-2 nanoparticles was observed by 1H NMR spectroscopy. It was suggested that clonazepam (CNZ) release kinetics were dominantly governed by diffusion mechanism.

Clonazepam↗
PubMed2000

Drug release from thermo-responsive self-assembled polymeric micelles composed of cholic acid and poly(N-isopropylacrylamide).

Cholic acid, conjugated with amine-terminated poly(N-isopropylacrylamide) (abbreviated as CA/ATPNIPAAm), was synthesized by a N, N'-dicyclohexyl carbodiimide (DCC)-mediated coupling reaction. Self-assembled CA/ATPNIPAAm micelles were prepared by a diafiltration method in aqueous media. The CA/ATPNIPAAm micelles exhibited a lower critical solution temperature (LCST) at 31.5 degrees C. Micelle sizes measured by photon correlation spectroscopy (PCS) were approximately 31.6+/-5.8 nm. The CA/ATPNIPAAm micelles were spherical and their thermal size transition was observed by transmission electron microscope (TEM). A fluorescence probe technique was used for determining the micelle formation behavior of CA/ATPNIPAAm in aqueous solutions using pyrene as a hydrophobic probe. The critical micelle concentration (CMC) was evaluated as 8.9 x 10(-2) g/L. A drug release study was performed using indomethacin (IN) as a hydrophobic model drug. The release kinetics of IN from the CA/ATPNIPAAm micelles revealed a thermo-sensitivity by the unique character of poly(N-isopropylacrylamide) i.e. the release rate was higher at 25 degrees C than at 37 degrees C.

Acrylic Resins↗
PubMed1999

Adriamycin release from flower-type polymeric micelle based on star-block copolymer composed of poly(gamma-benzyl L-glutamate) as the hydrophobic part and poly(ethylene oxide) as the hydrophilic part.

Star-block copolymer based on PBLG as the hydrophobic part and PEO as the hydrophilic one (as abbreviated GEG) was synthesized and characterized. Polymeric micelle was prepared by the diafiltration method. From the measurement of photon correlation spectroscopy, the nanoparticle sizes of GEG-1, GEG-2 and GEG-3 were 106.5+/-59.2, 43.8+/-0.7 and 13.5+/-1.0 nm in number average, respectively, indicating of the formation of polymeric micelle. Also, the nanoparticle sizes were dependent on the PBLG chain length, i.e. the more PBLG content in the copolymer, the larger the particle size. From the observation of transmission electron microscope(TEM), GEG-2 block copolymer had almost spherical shapes with size range about 20-70 nm, that was similar to particle size measurement. Fluorescence spectroscopy measurement indicated that GEG block copolymers associated in water to form polymeric micelles and critical micelle concentration (CMC) values of the block copolymers decreased with increasing PBLG chain length in the block copolymer. Characteristic peaks of the protons of the benzyl group in the PBLG and the methylene protons adjacent to the benzyl group of the PBLG segment in the GEG-2 nanoparticles appeared in 7.2 approximately 7.4 and 5.0 approximately 5.2 ppm, respectively, and disappeared in D(2)O, indicating the restricted motions of these protons within the micellar core and the very rigid structure of the PBLG core in the GEG polymeric micelles. Release of ADR from the polymeric micelles in vitro was slower in longer PBLG chain length and higher loading contents of ADR.

Antineoplastic Agents↗
PubMed1999

Self-assembling nanospheres of hydrophobized pullulans in water.

In this report, we have prepared self-assembling nanospheres of hydrophobized pullulans. Pullulan acetate as a hydrophobized pullulan was synthesized by acetylation of pullulan and characterized by Fourier transform infrared (FTIR) measurement. From the results of photon correlation spectroscopy (PCS), hydrophobized pullulans could be self-assembled in water as nanospherical aggregates, and their number-average particle size was 74.3 +/- 38.2 nm with a unimodal distribution. Also, morphological studies observed by transmission electron microscopy (TEM) showed that self-assembly of hydrophobized pullulans results in nice spherical shapes with a size range of about 50-100 nm, which was in accordance with PCS measurements. Their size and morphology have acceptable properties for intravenous injectable drug-targeting carriers. The fluorescence probe technique was used for self-association of hydrophobized pullulans in water using pyrene as a hydrophobic probe. From the fluorescence measurement, the fluorescence intensity of pyrene increased with increasing concentration of hydrophobized pullulans, which indicates self-assembly formation of hydrophobized pullulans in water. Also, in the fluorescence excitation spectrum, a red shift was observed with increasing concentration of hydrophobized pullulans. These results also revealed that hydrophobized pullulans could be self-assembled in water, and from the plot of I337/I334 versus log c of hydrophobized pullulans, the critical association concentration was 0.0022 g/l, which was considerably lower than that of low molecular weight surfactants or poloxamer. A drug loading study was performed using clonazepam (CNZ) as a hydrophobic model drug. We observed that the higher the feeding amount of drug was, the more the drug loading contents were, the lower the drug loading efficiency was, and the larger the particle size was. CNZ was released from nanospheres via pseudo-zero-order kinetics, and the increased drug loading contents led to slower release of the drug.

Absorptiometry, Photon↗
PubMed1998

Clonazepam release from core-shell type nanoparticles in vitro.

Block copolymers consisting of poly(gamma-benzyl L-glutamate) (PBLG) as the hydrophobic block and poly(ethylene oxide) (PEO) as the hydrophilic block were synthesized and characterized. Core-shell type nanoparticles of the block copolymers (abbreviated as GE) were prepared by the diafiltration method. The particle size diameter obtained by dynamic light scattering of GE-1 (PBLG content: 60.5 mol%), GE-2 (PBLG content: 40.0 mol %), GE-3 (PBLG content: 124.4 mol %) copolymer was 309.9 +/- 160.9, 251.9 +/- 220.6 and 200.5 +/- 177.1nm, respectively. The shape of the nanoparticles by SEM or TEM was almost spherical. The critical micelle concentration of the block copolymers obtained by fluorescence spectroscopy was dependent on the chain length of hydrophobic PBLG. The micelle structure of the copolymers nanoparticle was very stable against sodium dodecyl sulfate. Clonazepam (CZ) was loaded onto the core part of the nanoparticle as the crystalline state. Release of CZ from the nanoparticles in vitro was dependent on the drug loading contents and PBLG chain length.

Anticonvulsants↗
PubMed1998

Clonazepam release from poly(DL-lactide-co-glycolide) nanoparticles prepared by dialysis method.

Aim of this work is to prepare poly(DL-lactide-co-glycolide) (PLGA) nanoparticles by dialysis method without surfactant and to investigate drug loading capacity and drug release. The size of PLGA nanoparticles was 269.9 +/- 118.7 nm in intensity average and the morphology of PLGA nanoparticles was spherical shape from the observation of SEM and TEM. In the effect of drug loading contents on the particle size distribution, PLGA nanoparticles were monomodal pattern with narrow size distribution in the empty and lower drug loading nanoparticles whereas bi- or trimodal pattern was showed in the higher drug loading ones. Release of clonazepam from PLGA nanoparticles with higher drug loading contents was slower than that with lower loading contents.

Clonazepam↗
PubMed1997

Simple preparation of nanoparticles coated with carbohydrate-carrying polymers.

Nanoparticles bearing carbohydrate chains on the surface can be prepared by the simple diafiltration method. The nanoparticles prepared by the present method displayed high yield, no-aggregation formation, small size, narrow size distribution, and one-step procedure. Also, the high density carbohydrate chains on the particles can be recognized by liver cells.

Animals↗
PubMedDate not supplied

[A clinical study for promoting quality nursing care in a university hospital].

The purpose of this study was to develop a new nursing unit which can meet changing health care needs, enhance patients' satisfaction and nurses' job satisfaction, and finally guarantee quality nursing care with present manpower. For this, one medical unit was selected as a unit for quality care. And one medical unit which is similar in staffing and patients' characteristics was selected as a control unit. To assess present problems and identify the remedies to the problems a hospital-wide survey and a workshop were performed. According to the survey results, educational programs and improvement of the facilities and equipment supply system, managerial support for interdepartmental cooperation and intensification of bed-side nursing care were adopted as main principles for operating model unit. This model unit was operated for 3 months from Sep. 1, 1992 to Nov. 30, 1992. To evaluate the effectiveness of the model unit, direct/indirect nursing care hours, patients' satisfaction to nursing care, nurses' job satisfaction, and quality care index were measured. Direct/indirect nursing care hours were compared with that of the control unit, and patients' and nurses' satisfaction and quality care index were measured before and after operating model unit and compared with each other. The results of the study were as follows; 1. In the model unit mean direct nursing care hours per each shift was 146.88 minutes and indirect nursing care hours was 354.72 minutes. The ratio of the direct nursing care hour to indirect nursing hour was 29.6:70.4 and that of the control unit was 26.9:73.1. Direct nursing care hour in model unit was longer than that of the control unit. But, the difference was not significant. In subcategories of direct nursing care, the time spent in mobility and exercise, conservation of body temperature, hygiene, and communication and health education were longer than that of the control unit. 2. Indirect nursing care hour in model unit was shorter than that of the control unit. But, the difference was not significant. In subcategories of indirect nursing care, the time spent in drug management and ward arrangement was shorter than that of the control unit. 3. Patients' satisfaction to nursing care was increased significantly after operating the model unit (T = -3.48, P = 0.002) and satisfaction to subcategories of physical comfort measure, psychological care, and unit management components were significantly higher than before.(ABSTRACT TRUNCATED AT 400 WORDS)

Hospitals, University↗