Won Seok Lyoo

Development of polyvinyl alcohol–sodium alginate gel-matrix-based wound dressing system containing nitrofurazone

Polyvinyl alcohol (PVA)/sodium alginate (SA) hydrogel matrix-based wound dressing systems containing nitrofurazone (NFZ), a topical anti-infective drug, were developed using freeze-thawing method. Aqueous solutions of nitrofurazone and PVA/SA mixtures in different weight ratios were mixed homogeneously, placed in petri dishes, freezed at -20 degrees C for 18h and thawed at room temperature for 6h, for three consecutive cycles, and evaluated for swelling ratio, tensile strength, elongation and thermal stability of the hydrogel. Furthermore, the drug release from this nitrofurazone-loaded hydrogel, in vitro protein adsorption test and in vivo wound healing observations in rats were performed. Increased SA concentration decreased the gelation%, maximum strength and break elongation, but it resulted into an increment in the swelling ability, elasticity and thermal stability of hydrogel film. However, SA had insignificant effect on the release of nitrofurazone. The amounts of proteins adsorbed on hydrogel were increased with increasing sodium alginate ratio, indicating the reduced blood compatibility. In vivo experiments showed that this hydrogel improved the healing rate of artificial wounds in rats. Thus, PVA/SA hydrogel matrix based wound dressing systems containing nitrofurazone could be a novel approach in wound care.

Gel characterisation and in vivo evaluation of minocycline-loaded wound dressing with enhanced wound healing using polyvinyl alcohol and chitosan.

The purpose of this study was to develop a minocycline-loaded wound dressing with an enhanced healing effect. The cross-linked hydrogel films were prepared with polyvinyl alcohol (PVA) and chitosan using the freeze-thawing method. Their gel properties, in vitro protein adsorption, release, in vivo wound healing effect and histopathology were then evaluated. Chitosan decreased the gel fraction, maximum strength and thermal stability of PVA hydrogel, while it increased the swelling ability, water vapour transmission rate, elasticity and porosity of PVA hydrogel. Incorporation of minocycline (0.25%) did not affect the gel properties, and chitosan hardly affected drug release and protein adsorption. Furthermore, the minocycline-loaded wound dressing composed of 5% PVA, 0.75% chitosan and 0.25% drug was more swellable, flexible and elastic than PVA alone because of relatively weak cross-linking interaction of chitosan with PVA. In wound healing test, this minocycline-loaded PVA-chitosan hydrogel showed faster healing of the wound made in rat dorsum than the conventional product or the control (sterile gauze) due to antifungal activity of chitosan. In particular, from the histological examination, the healing effect of minocycline-loaded hydrogel was greater than that of the drug-loaded hydrogel, indicating the potential healing effect of minocycline. Thus, the minocycline-loaded wound dressing composed of 5% PVA, 0.75% chitosan and 0.25% drug is a potential wound dressing with excellent forming and enhanced wound healing.

Preparation and lead ion removal property of hydroxyapatite/polyacrylamide composite hydrogels

We report the synthesis of hydroxyapatite/polyacrylamide (HAp/PAAm) composite hydrogels with various HAp contents by free radical polymerization and their removal capability of Pb(2+) ions in aqueous solutions with controlled initial Pb(2+) ion concentrations and pH values of 2-5. The swelling ratio of the composite gels in aqueous solutions decreases with increasing the HAp content in the gels. The composite gel with higher HAp content exhibits the higher removal capacity of Pb(2+) ions owing to the higher adsorption sites for Pb(2+) ions, but shows the slower removal rate of Pb(2+) ions due to the lower degree of swelling. The removal mechanism of Pb(2+) ion is very sensitive to the pH value in aqueous solution, although the removed amount of Pb(2+) ion is nearly same, regardless of pH values of 2-5. The removal mechanism, the dissolution of HAp in the composite gel and subsequent precipitation of hydroxypyromorphite (HPy), is dominant at lower pH 2-3, whereas the mechanism, the adsorption of Pb(2+) ions on the composite gel and following cation exchange reaction between Pb(2+) ions adsorbed and Ca(2+) of HAp, is dominant at higher pH 4-5. The equilibrium removal process of Pb(2+) ions by the composite gels at pH 5 is described well with the Langmuir isotherm model. The equilibrium removal capacities of the composite gels with 30, 50, and 70 wt.% HAp contents are evaluated to be 123, 178, and 209 mg/g, respectively.

Superhydrophobicity of PHBV fibrous surface with bead-on-string structure

A poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) fibrous surface with various bead-on-string structures was fabricated by electrospinning. PHBV was electrospun at various concentrations and then CF4 plasma treatment was employed to further improve the hydrophobicity of the PHBV fiber surfaces. The surface morphology of the electrospun PHBV mats was observed by scanning electron microscopy (SEM). The surface properties were characterized by water contact angle (WCA) measurements and X-ray photoelectron spectroscopy (XPS). The surface morphology of the electrospun PHBV fibrous mats with the bead-son-string structure varied with the solution concentration. The WCA of all of the electrospun PHBV mats was higher than that of the PHBV film. In particular, a very rough fiber surface including porous beads was observed when PHBV was electrospun from the solution with a concentration of 26 wt%. Also, its WCA further increased from 141 degrees to 158 degrees after CF(4) plasma treatment for 150 s. PHBV can be rendered superhydrophobic by controlling the surface morphology and surface energy, which can be achieved by adjusting the electrospinning and plasma treatment conditions.

Gentamicin-Loaded Wound Dressing With Polyvinyl Alcohol/Dextran Hydrogel: Gel Characterization and In Vivo Healing Evaluation

To develop a gentamicin-loaded wound dressing, cross-linked hydrogel films were prepared with polyvinyl alcohol (PVA) and dextran using the freezing–thawing method. Their gel properties such as gel fraction, swelling, water vapor transmission test, morphology, tensile strength, and thermal property were investigated. In vitro protein adsorption test, in vivo wound healing test, and histopathology were performed. Dextran decreased the gel fraction, maximum strength, and thermal stability of hydrogels. However, it increased the swelling ability, water vapor transmission rate, elasticity, porosity, and protein adsorption. The drug gave a little positive effect on the gel properties of hydrogels. The gentamicin-loaded wound dressing composed of 2.5% PVA, 1.13% dextran, and 0.1% drug was more swellable, flexible, and elastic than that with only PVA because of its cross-linking interaction with PVA. In particular, it could provide an adequate level of moisture and build up the exudates on the wound area. From the in vivo wound healing and histological results, this gentamicin-loaded wound dressing enhanced the healing effect more compared to conventional product because of the potential healing effect of gentamicin. Thus, this gentamicin-loaded wound dressing would be used as a potential wound dressing with excellent forming and improved healing effect in wound care.

Superhydrophobic PLA fabrics prepared by UV photo-grafting of hydrophobic silica particles possessing vinyl groups

Superhydrophobic poly(lactic acid) (PLA) fabrics are prepared by UV photo-grafting of hydrophobic silica particles possessing vinyl functional groups on the surfaces, which is a novel one-step process to provide surface with roughness as well as hydrophobicity simultaneously. For this purpose, hydrophobic silica particles with vinyl groups and average diameter of 1.51+/-0.05 microm are synthesized via a sol-gel process. The silica particles possessing vinyl groups are found to be effectively immobilized on PLA fabrics via UV photo-grafting reaction. The water contact angle of the treated PLA fabric is measured to be approximately 150 degrees, which is high enough to exhibit the Lotus effect as a result of the superhydrophobicity.

Anti-inflammatory action of mollugin and its synthetic derivatives in HT-29 human colonic epithelial cells is mediated through inhibition of NF-κB activation

Mollugin is the active compound of Rubia cordifolia, which has been used as a traditional Chinese medicine for the treatment of various inflammatory diseases including arthritis and uteritis. In the present study, we investigated for the first time the inhibitory effects and the mechanisms of action of mollugin (M1) and its synthetic derivatives (M2-M4) on tumor necrosis factor (TNF)-alpha-induced inflammatory responses in HT-29 human colon epithelial cells. Treatment with M1 and its derivatives M2-M4 significantly inhibited TNF-alpha-induced attachment of U937 monocytic cells to HT-29 cells, which mimics the initial phase of colon inflammation. TNF-alpha-induced mRNA induction of the chemokines, monocyte chemoattractant protein (MCP)-1 and interleukin (IL)-8, and the intercellular cell adhesion molecule (ICAM)-1, which are involved in adhesion between leukocytes and epithelial cells, was suppressed by M1-M4, and M1 was the most efficacious. In addition, M1-M4 significantly suppressed TNF-alpha-induced NF-kappaB transcriptional activity. Such NF-kappaB inhibitory activity of M1-M4 (20 microM) correlated with their ability to suppress TNF-alpha-induced chemokine expression and U937 monocytic cell adhesion to HT-29 colonic epithelial cells. Treatment of HT-29 cells with M1 and PDTC, a NF-kappaB inhibitor, synergistically suppressed both TNF-alpha-induced NF-kappaB activation and monocytic cell adhesion to HT-29 cells. These results suggest that M1-M4 inhibit TNF-alpha-induced expression of inflammatory molecules via NF-kappaB, and that M1, a potent NF-kappaB inhibitor, may be a valuable new drug candidate for the treatment of colon inflammation.

Effects of polymer concentration and zone drawing on the structure and properties of biodegradable poly(butylene succinate) film

To produce various biodegradable poly(butylene succinate) (PBS) films for particular use, the effects of initial polymer concentration and zone drawing on the structure, physical properties, and hydrolytic degradation of PBS film were investigated. PBS films were prepared from chloroform solutions with different initial concentrations of 8, 11, 14, 17 and 20 g/dl. In order to investigate the drawing behavior of the PBS films with different solution concentrations, the films were drawn under various zone drawing conditions. Through a series of experiments, it turned out that the initial concentration of PBS solution in chloroform caused significant changes in the draw ratio of the PBS film. That is, the zone draw ratios of the film at initial concentration of 14 g/dl exhibited its maximum values and gradually decreased at higher or lower concentrations. Thus, it was concluded that the initial concentration of 14 g/dl is the optimum polymer concentration to produce maximum draw ratio in this work. In addition, the crystal and amorphous orientations and tensile properties of PBS film having similar draw ratio and similar crystallinity were highest at 14 g/dl and surface crystal morphologies of these films were absolutely different. The hydrolytic degradation rate of the film at 14 g/dl was lowest, but with similar draw ratio, film dimension, and crystallinity, indicating that the degradation behaviors were greatly affected by the initial polymer concentration, orientation, and crystal morphology.

Characterizations of poly(vinyl pivalate) polymerized in tertiary butyl alcohol and resulting syndiotactic poly(vinyl alcohol) microfibrils saponified

Abstract Vinyl pivalate (VPi) was solution-polymerized in tertiary butyl alcohol (TBA) and in dimethyl sulfoxide (DMSO) with low chain transfer constant using a low temperature initiator, 2,2′-azobis(2,4-dimethylvaleronitrile) (ADMVN). TBA was absolutely superior to DMSO in increasing the syndiotacticity and molecular weight of poly(vinyl alcohol) (PVA). Low-temperature solution polymerization of VPi in TBA or DMSO by adopting ADMVN proved to be successful in obtaining PVA of ultrahigh molecular weight (maximum number-average degree of polymerization ( P n ): 13,500–17,000) and of high yield (ultimate conversion of VPi into PVPi: 55–80%) to a much higher conversion than that from bulk polymerization. Moreover, PVA from TBA system were fibrous, with a high degree of orientation of the crystallites, indicating the syndiotactic nature of TBA polymerization.

Enhanced Oral Bioavailability of Piroxicam in Rats by Hyaluronate Microspheres

ABSTRACT To enhance the dissolution and oral bioavailability of poorly water soluble piroxicam, the piroxicam-loaded hyaluronic microspheres were prepared with various ratios of piroxicam, sodium hyaluronate and polyethylene glycol 4000 (PEG) using a spray dryer, and their physicochemical properties such as shape, size, drug-loading efficiency and dissolution were investigated. The pharmacokinetic study of piroxicam-loaded hyaluronic micropheres in rats was then performed compared to piroxicam powder. The piroxicam-loaded hyaluronic microspheres, spherical in shape, had the geometric mean diameters of about 1.5 μm and drug loading efficiency of about 90%, irrespective of ratio of piroxicam/sodium hyaluronate/PEG. The hyaluronic microspheres containing PEG gave significantly higher dissolution rates of drug than did piroxicam powder, PEG-based solid dispersion system and hyaluronic microspheres without PEG, suggesting that the hyaluronic microsphere with sodium hyaluronate and PEG was more useful for improving the dissolution rate of poorly water soluble piroxicam. The piroxicam-loaded hyaluronic microcapsule composed of (piroxicam/sodium hyaluronate/PEG; 2: 20: 1) gave about threefold improved dissolution of drug in water for 4 h compared to piroxicam powder. It showed higher plasma concentrations of drug compared to piroxicam powder. It gave significantly higher AUC and faster Tmax of piroxicam than did piroxicam powder. In particular, the AUC of piroxicam from hyaluronic microsphere was about twofold higher than that from piroxicam powder, suggesting that it could enhance the oral bioavailability of piroxicam. Thus, the hyaluronic microsphere developed using spray-drying technique with sodium hyaluronate and PEG was a more effective oral dosage form for poorly water soluble piroxicam.