Biomedical subjects

Chong-Kook Kim

Publications and source records attributed to Chong-Kook Kim.

49 records · Page 3Linked to original sources

PubMed2003

Physicochemical characterization of diclofenac sodium-loaded poloxamer gel as a rectal delivery system with fast absorption.

Rectal poloxamer gel systems composed of poloxamers and bioadhesive polymers were easy to administer to the anus and were mucoadhesive to the rectal tissues without leakage after the dose. However, a poloxamer gel containing diclofenac sodium could not be developed using bioadhesive polymers, since the drug was precipitated in this preparation. To develop a poloxamer gel using sodium chloride instead of bioadhesive polymers, the physicochemical properties such as gelation temperature, gel strength, and bioadhesive force of various formulations composed of diclofenac sodium, poloxamers, and sodium chloride were investigated. Furthermore, the pharmacokinetic study of diclofenac sodium delivered by the poloxamer gel was performed. Diclofenac sodium significantly increased the gelation temperature and weakened the gel strength and bioadhesive force, while sodium chloride did the opposite. The poloxamer gels with less than 1.0% sodium chloride, in which the drug was not precipitated, were inserted into the rectum without difficulty and leakage, and were retained in the rectum of rats for at least 6 hr. Furthermore, poloxamer gel gave significantly higher initial plasma concentrations and faster Tmax of diclofenac sodium than did solid suppository, indicating that drug from poloxamer gel could be absorbed faster than that from the solid one in rats. Our results suggested that a rectal poloxamer gel system with sodium chloride and poloxamers was a more physically stable, convenient, and effective rectal dosage form for diclofenac sodium.

Adhesiveness↗

PubMed2003

Enhancement of polyethylene glycol (PEG)-modified cationic liposome-mediated gene deliveries: effects on serum stability and transfection efficiency.

In this study, we modified cationic liposomes either by polyethylene glycol (PEG)-grafting or PEG-adding methods, and compared the physical properties of transfection complexes and transfection efficiency in-vitro and prolonged circulation in-vivo. The PEG-grafted transfection complexes were prepared by mixing plasmid DNA with PEG-grafted cationic liposomes, which were composed of DSPE-PEG 2000 and cationic lipids. The PEG-added transfection complexes were prepared by adding DSPE-PEG 2000 to the mixture of cationic liposomes and plasmid DNA. The particle sizes of the PEG-modified transfection complexes (approximately 200 nm) changed a little over 4 weeks compared with the conventional transfection complexes. In the presence of serum, the transfection efficiency of the conventional transfection complexes was lowered whereas the transfection efficiency of the PEG-modified transfection complexes was maintained. Moreover, the transfection efficiency of the conventional transfection complexes was significantly reduced when they were stored. However, the transfection efficiency was stable for the PEG-modified transfection complexes, even after two weeks of storage. Of the in-vitro transfection efficiencies, there was no difference between PEG-grafted and PEG-added transfection complexes. When the conventional, PEG-grafted, and PEG-added transfection complexes were administered into mice by the tail vein, the PEG-added transfection complexes showed a prolonged circulation of plasmid DNA compared with other transfection complexes. These results suggest that the PEG-added transfection complexes could be a useful non-viral vector because of their simplicity in preparation, enhanced stability and prolonged circulation compared with the conventional transfection complexes.

Cations↗

PubMed2003

1,3-selenazol-4-one derivatives inhibit inducible nitric oxide-mediated nitric oxide production in lipopolysaccharide-induced BV-2 cells.

Activated microglia extensively produce nitric oxide (NO) by inducing expression of inducible NO synthase (iNOS). NO plays a deleterious role in brain inflammation and neuronal death. In the present study, we investigated the effects of 1,3-selenazol-4-one derivatives (Sz-A, B, C, D and E) on NO production and iNOS expression in lipopolysaccharide (LPS)-induced BV-2 cells, a murine microglia cell line. Among these compounds, Sz-B and C remarkably inhibited LPS-induced NO production relative to that of Sz-A, D, and E at 5 microM in BV-2 cells. Sz-B and C dose-dependently inhibited NO production at 1, 5, and 10 microM without toxicity to BV-2 cells. Sz-B and C also dose-dependently suppressed iNOS expression at the same concentrations in LPS-induced BV-2 cells. This result suggests that Sz-B and C inhibit iNOS-mediated NO production in LPS-induced BV-2 cells. Structurally, Sz-B and C bear an ethyl or methyl group at the 5 positions of the 4-selenazolone skeletons, which could play an important role in inhibiting iNOS-mediated NO production.

Animals↗

PubMed2002

Cyclosporin A enhances the apoptotic effects of N-(4-hydroxyphenyl)retinamide in breast cancer cells.

4HPR, an analogue of ATRA, effectively induces growth inhibition and apoptosis in breast cancer cell lines and animal models but is ineffective against advanced human breast tumors. Different compounds, including tamoxifen, are currently being tested to increase 4HPR efficacy in the clinic. Here, we report that cyclosporin A selectively increases the ability of 4HPR, but not ATRA, to induce growth inhibition and apoptosis in ER(+) and ER(-) breast cancer cell lines. Increased apoptosis by the 4HPR and cyclosporin A combination was correlated with increased production of the free radical nitric oxide. Thus, the 4HPR and cyclosporin A combination may potentially be a novel therapeutic modality against breast tumors.

Antineoplastic Agents↗

PubMed2002

Formulation parameters determining the physicochemical characteristics of solid lipid nanoparticles loaded with all-trans retinoic acid.

Solid lipid nanoparticles (SLNs) have gained attention as a colloidal drug carrier, particularly for drugs with limited solubility. The poor aqueous solubility of all-trans retinoic acid (ATRA) has been a limiting factor in its clinical use. This study was undertaken to overcome the solubility limitation of ATRA by loading in SLNs. The physicochemical characteristics of ATRA-loaded SLNs were investigated by particle size analysis, zeta potential measurement, thermal analysis and HPLC determination of ATRA content. The mean particle size of ATRA-loaded SLNs could be reduced (1) by mixing EggPC and Tween 80 as a surfactant and (2) by increasing the total surfactant amount. The smallest mean particle size of SLNs was obtained with 50 mg/g surfactant mixture composed of 54:46% (w/w) EggPC:Tween 80 (154.9 nm). The zeta potential of SLNs could be increased by mixing EggPC, Tween 80 and DSPE-PEG in the surfactant mixture. The zeta potential of SLNs prepared with 50 mg/g surfactant mixture composed of 48:6:46% (w/w) of EggPC:DSPE-PEG:Tween 80 was -38.18 mV. ATRA could be loaded at 2.4% (percentage of lipid matrix) on these SLNs without impairing their physical stability. After freeze-drying, the mean particle size and polydispersity index of ATRA-loaded SLNs were only slightly increased (181.8 vs. 265.2 nm, 0.173 vs. 0.200). Furthermore, no significant change was observed in the SLN-loaded concentration of ATRA and the zeta potential of SLNs after freeze-drying. Taken together, SLN formulation of ATRA with similar characteristics to those of parenteral emulsions could be obtained even after freeze-drying.

Antineoplastic Agents↗

PubMed2002

Prolonged antifungal effects of clotrimazole-containing mucoadhesive thermosensitive gels on vaginitis.

To develop more effective treatment for vaginal candidasis, clotrimazole (CT) was formulated in mucoadhesive thermosensitive gels (MTG). Several MTG formulations composed of poloxamers (P) 407, 188, and polycarbophil (PC) were prepared. P188 and PC increased the mucoadhesiveness but reduced the syringebility of liquid forms of the gels. Based on the balance between the mucoadhesiveness and syringebility, MTG composed of P407/P188/PC (15/15/0.2 or 15/20/0.2) were further studied. Of the two MTG, the formulation with 15% of P188 gelled at higher temperature and revealed lower elastic modulus. In vitro, sustained release of CT from MTG was observed. In vivo antifungal activity of CT, tested against Candida albicans vaginitis in female rats, was significantly prolonged after vaginal delivery using MTG. At 10 days post-dose, the c.f.u. of C. albicans was more than 10(4)-fold decreased in MTG-treated groups. Moreover, the vaginal delivery of CT in MTG enhanced the viability of epithelial cells without affecting the morphology of vaginal mucosa. These results indicate that CT-containing vaginal MTG might be further developed for safe, convenient, and effective treatment of vaginal candidasis with reduced dosing interval.

Adhesives↗

PubMed2002

Rheological evaluation of thermosensitive and mucoadhesive vaginal gels in physiological conditions.

The timely gelation and retention of in situ-gelling vaginal formulations would be fundamental to improve the efficacy of drugs. In this study, various rheological properties of clotrimazole gels were evaluated for predicting their performance in vagina. Two kinds of thermosensitive and mucoadhesive formulations were composed of poloxamer 407 (P407, 15%), polycarbophil (0.2%), and different amounts of P188 (15 vs. 20%). Both formulations were Newtonian at 20 degrees C but non-Newtonian at 37 degrees C. Although both liquid formulations gelled below the vaginal temperature, they differed in gelation time and viscoelastic properties in the presence of vaginal fluid simulant. At body temperature, the formulation with 20% of P188 gelled within 35 s but it took two times longer for the other one gelled. Upon dilution with simulated vaginal fluid, the formulation with 20% of P188 retained the rheology of a gel, but the other one lost the viscoelastic properties typical for a gel. Moreover, after dilution with simulated vaginal fluid, the elastic modulus was orders of magnitude higher in the formulations with 20% of P188 relative to the other one. These results indicate that the rheological evaluation at the physiologic conditions needs to be preceded to develop more effective in situ-gelling vaginal formulations.

Acrylic Resins↗

PubMed2002

In situ gelling and mucoadhesive polymer vehicles for controlled intranasal delivery of plasmid DNA.

Nasal administration of plasmid DNA is emerging as a new route of delivery for therapeutic genes and DNA vaccines. To improve the intranasal absorption of plasmid DNA, we designed delivery systems composed of in situ gelling and mucoadhesive polymers. Poloxamers (Pol) were used to provide in situ gelling property. Polycarbophil (PC) or polyethylene oxide (PEO) was used as mucoadhesive polymers. The gelation temperatures of the formulations slightly decreased by the mucoadhesive polymers, but not by plasmid DNA. The in vitro release of plasmid DNA from the gels followed Fickian diffusion. The absorption of plasmid DNA varied with the contents and type of mucoadhesive polymers. Of vehicles, Pol/PC 0.2% showed the highest absorption with an area under the curve value 11-fold higher than saline, the conventional vehicle. The nasal retention of plasmid DNA was highly prolonged by mucoadhesive polymers. At 3 h postdose, the nasal tissue levels of plasmid DNA given in Pol/PC and Pol/PEO 0.8% were 10- and 40-fold higher relative to saline. The histopathology of nasal tissues was not altered after repeated dosing over 2 weeks. The mRNA expression of plasmid DNA delivered by Pol or Pol/PEO 0.4% was observed in the nasal tissues. These results indicate that the nasal absorption of plasmid DNA can be effectively and safely enhanced by using in situ gelling and mucoadhesive polymer-based vehicles.

Adhesives↗

PubMed2002

Recent progress in drug delivery systems for anticancer agents.

Recent progress in understanding the molecular basis of cancer brought out new materials such as oligonucleotides, genes, peptides and proteins as a source of new anticancer agents. Due to their macromolecular properties, however, new strategies of delivery for them are required to achieve their full therapeutic efficacy in clinical setting. Development of improved dosage forms of currently marketed anticancer drugs can also enhance their therapeutic values. Currently developed delivery systems for anticancer agents include colloidal systems (liposomes, emulsions, nanoparticles and micelles), polymer implants and polymer conjugates. These delivery systems have been able to provide enhanced therapeutic activity and reduced toxicity of anticancer agents mainly by altering their pharmacokinetics and biodistribution. Furthermore, the identification of cell-specific receptor/antigens on cancer cells have brought the development of ligand- or antibody-bearing delivery systems which can be targeted to cancer cells by specific binding to receptors or antigens. They have exhibited specific and selective delivery of anticancer agents to cancer. As a consequence of extensive research, clinical development of anticancer agents utilizing various delivery systems is undergoing worldwide. New technologies and multidisciplinary expertise to develop advanced drug delivery systems, applicable to a wide range of anticancer agents, may eventually lead to an effective cancer therapy in the future.

Antineoplastic Agents↗

PubMed2002

Microemulsion formulation of clonixic acid: solubility enhancement and pain reduction.

Clonixic acid is currently marketed as a salt form because of its poor water-solubility. However, the commercial dosage form causes severe pain after intramuscular or intravenous injection. To improve the solubility of clonixic acid and to reduce pain on injection, clonixic acid was incorporated into oil-in-water microemulsions prepared from pre-microemulsion concentrate composed of varying ratios of oil and surfactant mixture. As an oil phase for drug incorporation, up to 14% castor oil could be included in the pre-microemulsion concentrate without a significant increase in droplet size. Both drug contents and droplet size increased as the weight ratio of Tween 20 to Tween 85 decreased. Taken together, when microemulsions were prepared from pre-microemulsion concentrate composed of 5:12:18 weight ratio of castor oil:Tween 20:Tween 85, clonixic acid could be incorporated at 3.2 mg mL(-1) in the microemulsion with a droplet size of less than 120 nm. The osmotic pressure of this microemulsion was remarkably lower than the commercial formulation, irrespective of the dilution ratios. The rat paw-lick test was used to compare pain responses among formulations. The microemulsion formulation significantly reduced the number of rats licking their paws as well as the total licking time, suggesting less pain induction by the microemulsion formulation. The pharmacokinetic parameters of clonixic acid after intravenous administration of the clonixic acid microemulsion to rats were not significantly different from those of the commercial formulation, lysine clonixinate. The present study suggests that microemulsion is an alternative formulation for clonixic acid with improved characteristics.

Animals↗

PubMed2002

pH-sensitive, serum-stable and long-circulating liposomes as a new drug delivery system.

The lack of stability in blood and the short blood circulation time of pH-sensitive liposomes are major drawbacks for their application in-vivo. To develop pH-sensitive, serum-stable and long-circulating liposomes as drug delivery systems, the impact of polyethylene glycol-derived phosphatidylethanolamine (DSPE-PEG) on the properties of pH-sensitive liposomes was investigated. pH-sensitive liposomes were prepared with dioleoylphosphatidylethanolamine (DOPE) and oleic acid (DOPE/oleic acid liposome) or DOPE and 1,2-dipalmitoylsuccinylglycerol (DOPE/DPSG liposome). The inclusion of DSPE-PEG enhanced the serum stability of both DOPE/oleic acid and DOPE/DPSG liposomes, but also shifted the pH-response curve of pH-sensitive liposomes to more acidic regions and reduced the maximum leakage percentage. The impact of DSPE-PEG, however, was much lower in the DOPE/DPSG liposomes than in the DOPE/oleic acid liposomes. In tumour tissue homogenates, where the pH is lower than normal healthy tissues, the pH-sensitive DOPE/DPSG liposomes released the entrapped markers rapidly, in comparison with pH-insensitive dipalmitoylphosphatidylcholine/cholesterol/DSPE-PEG liposomes. Moreover, the release rate was not affected by the content of DSPE-PEG. The blood circulation time of methotrexate incorporated in DOPE/UDPSG liposomes was significantly prolonged with increasing content of DSPE-PEG. Taken together, the liposomes composed of DOPE, DPSG and DSPE-PEG (up to 5%) were pH sensitive, plasma stable and had a long circulation time in the blood. The complete destabilization of the liposomes at tumour tissues suggests that the liposomes might be useful for the targeted delivery of drugs such as anticancer agents.

Analysis of Variance↗

PubMedDate not supplied

Effect of chemical modification on the pharmacokinetics and biodistribution of carboxymethyl dextran as a drug carrier.

The in vivo fate of drugs conjugated to macromolecules inevitably depends on that of macromolecules. However, the in vivo fate of macromolecules also may be altered by conjugation to drugs. For the efficient design of carboxymethyldextran (CMD) conjugates of a new analgesic drug, DA5018, we investigated whether the chemical modifications alter the pharmacokinetics and tissue distribution of CMD itself. [(14)C]CMD, oxidized [(14)C]CMD ([(14)C]OCMD), [(14)C]OCMD conjugates of DA5018 ([(14)C]OCMD-DA5018) and [(14)C]OCMD conjugates of ethanolamine ([(14)C]OCMD-EA) were prepared and their molecular sizes were compared by size exclusion HPLC. The pharmacokinetics, biliary excretion, and tissue distribution of total radioactivity were compared after intravenous administration of each CMD derivative, 2.0 MBq/kg, to rats. The effective molecular sizes of CMD derivatives decreased in the order of [(14)C]CMD, [(14)C]OCMD-DA5018, [(14)C]OCMD, and [(14)C]OCMD-EA. After administration of each derivative, the mean AUC values of total radioactivity decreased with the decrease in the effective molecular size. The values of CL, Vss, and the amount of total radioactivity excreted in 24-hr urine increased considerably with the decrease in the effective molecular size. The tissue-to-plasma ratios of total radioactivity remaining in heart, liver, lung, kidney, and spleen at 24 hr also increased in the opposite order of the effective molecular size. Taken together, all these results demonstrate that the chemical modifications and physicochemical properties of attached chemicals can alter the pharmacokinetics and tissue distribution of CMD. One possible reason might be the difference in the effective molecular size of various CMD derivatives. Our study demonstrates that it may be necessary to consider the effect of chemical modification on the in vivo fate of macromolecules in designing macromolecular drug conjugates.

Animals↗

PubMedDate not supplied

Improved solubility and in vitro dissolution of Ibuprofen from poloxamer gel using eutectic mixture with menthol.

To improve the solubility and in vitro dissolution of poorly water-soluble ibuprofen with poloxamer and menthol, the effects of menthol and poloxamer 188 on the aqueous solubility of ibuprofen were investigated. The dissolution study of ibuprofen delivered by poloxamer gels composed of poloxamer 188 and menthol were performed. In the absence of poloxamer, the solubility of ibuprofen increased until the ratio of menthol to ibuprofen increased from 0:10 to 4:6, followed by an abrupt decrease in solubility above the ratio of 4:6, indicating that 4 parts of ibuprofen formed eutectic mixture with 6 parts of menthol. In the presence of poloxamer 188, the solutions with the same ratio of menthol to ibuprofen showed abrupt increase in the solubility of ibuprofen. Furthermore, the solution with ratio of 4:6 showed more than 2.5- and 6-fold increase in the solubility of ibuprofen compared with that without poloxamer and that without menthol, respectively. The poloxamer gel with menthol/ibuprofen ratio of 1:9 and higher than 15% poloxamer 188 showed the maximum solubility of ibuprofen, 1.2 mg/ml. Menthol improved the dissolution rates of ibuprofen from poloxamer gels. Dissolution mechanism showed that the dissolution rate of ibuprofen from the poloxamer gels without menthol was independent of the time, but the drug might be dissolved from the poloxamer gels with menthol by Fickian diffusion. Thus, the poloxamer gels developed using eutectic mixture with menthol, which gave the improved solubility and dissolution of drug, are potential candidates for ibuprofen-loaded transdermal and rectal delivery system.

Anti-Inflammatory Agents, Non-Steroidal↗