Search PubMed⌕ Search

Biomedical subjects

I K Kang

Publications and source records attributed to I K Kang.

At least 19 recordsLinked to original sources
PubMed2005

Morphology and metabolism of hepatocytes microencapsulated with acrylic terpolymer-alginate using gelatin and poly(vinyl alcohol) as extracellular matrices.

Microcapsules with good mechanical stability were prepared using an appropriate mixture of alginate and acrylic terpolymer. It was found from the microscopic observation that the microcapsules had a porous structure with interconnected pores, with a size of 50-150 nm. The results of the permeability experiment of microcapsules using FITC-dextrans showed that the capsule had a molecular mass cut-off of 120 kDa. The hepatocytes encapsulated in both alginate and acrylic terpolymer with gelatin and PVA rapidly aggregated in the core. The aggregated cells showed high albumin synthesis and ammonia removal, suggesting good metabolic function.

Acrylates↗
PubMed2003

Morphology and metabolism of Ba-alginate-encapsulated hepatocytes with galactosylated chitosan and poly(vinyl alcohol) as extracellular matrices.

Lactobionic acid, bearing a beta-galactose group, was coupled with chitosan to provide synthetic extracellular matrices together with poly(vinyl alcohol) (PVA). The hepatocytes encapsulated in Ba-alginate capsules with galactosylated chitosan (GC) and PVA as extracellular matrices showed aggregation morphologies as the incubation time increased. Ba-alginate-encapsulated hepatocytes with GC exhibited a higher metabolic function in albumin secretion compared to those entrapped in Ba-alginate beads and monolayer-cultured on a collagen-immobilized polystyrene dish. The ammonia removal ability of monolayer-cultured hepatocytes decreased with increasing culture time and disappeared completely after three days. In contrast, the ammonia removal ability of encapsulated and entrapped hepatocytes increased with increasing incubation time in the first seven and five days, respectively. Thereafter, the entrapped hepatocytes lost ammonia removal ability quickly while the encapsulated hepatocytes kept a relatively high ammonia removal ability up to 13 days. The trace amount of GC in the core matrices enabled encapsulated cells to enhance their ammonia removal and albumin secretion ability. The results obtained with 3-(3,4-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT) also showed that the capsules incorporated with GC can provide a better microenvironment for cell aggregation along with nutrition and metabolite transfer. Due to the nature of the liquid core, the encapsulated hepatocytes showed very good mobility. This facilitated cell-cell interaction and cell-matrix interaction.

Alginates↗
PubMed2001

Intracellular degradation of two structurally different polyhydroxyalkanoic acids accumulated in Pseudomonas putida and Pseudomonas citronellolis from mixtures of octanoic acid and 5-phenylvaleric acid.

From a set of mixed carbon sources, 5-phenylvaleric acid (PV) and octanoic acid (OA), polyhydroxyalkanoic acid (PHA) was separately accumulated in the two pseudomonads Pseudomonas putida BM01 and Pseudomonas citronellolis (ATCC 13674) to investigate any structural difference between the two PHA accumulated under a similar culture condition using one-step culture technique. The resulting polymers were isolated by chloroform solvent extraction and characterized by fractional precipitation and differential scanning calorimetry. The solvent fractionation analysis showed that the PHA synthesized by P. putida was separated into two fractions, 3-hydroxy-5-phenylvalerate (3HPV))-rich PHA fraction in the precipitate phase and 3-hydroxyoctanoate (3HO)-rich PHA fraction in the solution phase whereas the PHA produced by P. citronellolis exhibited a rather little compositional separation into the two phases. According to the thermal analysis, the P. putida PHA exhibited two glass transitions indicative of the PHA not being homogeneous whereas the P. citronellolis PHA exhibited only one glass transition. It was found that the structural heterogeneity of the P. putida PHA was caused by a significant difference in the assimilation rate between PV and OA. The structural heterogeneity present in the P. putida PHA was also confirmed by a first order degradation kinetics analysis of the PHA in the cells. The two different first-order degradation rate constants (k(1)), 0.087 and 0.015/h for 3HO- and 3HPV-unit, respectively, were observed in a polymer system over the first 20 h of degradation. In the later degradation period, the disappearance rate of 3HO-unit was calculated to be 0.020 h. The k(1) value of 0.083/h, almost the same as for the 3HO-unit in the P. putida PHA, was obtained for the P(3HO) accumulated in P. putida BM01 grown on OA as the only carbon source. In addition, the k(1) value of 0.015/h for the 3HPV-unit in the P. putida PHA, was also close to 0.019/h for the P(3HPV) homopolymer accumulated in P. putida BM01 grown on PV plus butyric acid. On the contrary, the k(1) values for the P. citronellolis PHA were determined to be 0.035 and 0.029/h for 3HO- and 3HPV-unit, respectively, thus these two relatively close values implying a random copolymer nature of the P. citronellolis PHA. In addition, the faster degradation of P(3HO) than P(3HPV) by the intracellular P. putida PHA depolymerase indicates that the enzyme is more specific against the aliphatic PHA than the aromatic PHA.

Calorimetry, Differential Scanning↗
PubMed2001

Surface modification of polyhydroxyalkanoate films and their interaction with human fibroblasts.

A poly(3-hydroxybutylate-co-hydroxyvalerate) (PHA) film containing 34 mol.% 3-hydroxyvalerate (Biopol D600P) was prepared by the solvent cast method using a 10 wt.% chloroform solution of PHA. The PHA film was exposed to an oxygen plasma glow discharge to produce peroxides on its surfaces. These peroxides were then used as catalysts for the polymerization of acrylic acid (AA) in order to prepare carboxyl group-introduced PHA (PHA-C). Insulin-immobilized PHA was prepared using the coupling reaction of PU-C with insulin. The surface-modified PHAs were then characterized by attenuated total reflection Fourier transform infrared spectroscopy, electron spectroscopy for chemical analysis, and a contact angle goniometer. The amounts of insulin directly coupled to the carboxyl groups on PHA-C and coupled to the terminus amino groups of the grafted polyethylene oxide were 2.9 and 0.8 microg cm(-2), respectively. The PHA water contact angle (75 degrees ) decreased with AA grafting (33 degrees ) and insulin immobilization (31 degrees ), thereby exhibiting the increased hydrophilicity of the modified PHAs. When compared with PHA and PHA-C, the proliferation of human fibroblasts in the presence of serum was significantly accelerated on the insulin-immobilized PHAs.

Acrylates↗
PubMed2001

Interaction of blood components with heparin-immobilized polyurethanes prepared by plasma glow discharge.

The blood compatibility of poly(ethylene oxide) (PEO)-grafted and heparin (Hep) immobilized polyurethanes was investigated using in vitro plasma recalcification time (PRT), activated partial thromboplastin time (APTT), platelet adhesion and activation, and peripheral blood mononuclear cell (PBMC) adhesion and activation. In the experiment with plasma proteins, the PRT of the polyurethane (PU) surface was prolonged by PEO grafting and further prolonged by heparin immobilization. The APTT was prolonged on PU-Hep, suggesting the binding of immobilized heparin to antithrombin III. The percentage of platelet adhesion on PU was not much different from that on acrylic acid- and PEO-grafted PUs (PU-C, PU-6, PU-33), yet was substantially decreased by heparin immobilization (PU-6-Hep, PU-33-Hep). The release of serotonin from adhering platelets was slightly suppressed on PEO-grafted PUs yet significantly suppressed on heparin-immobilized PUs. In the PBMC experiments, the adhesion and activation of the cells were significantly suppressed on heparin-immobilized PUs, and the amount of interleukin-6 (IL-6) released from PBMCs stimulated with surface-modified PUs decreased with a decrease in PBMC adhesion.

Biocompatible Materials↗
PubMed2000

Surface characterization and in vitro blood compatibility of poly(ethylene terephthalate) immobilized with insulin and/or heparin using plasma glow discharge.

Poly(ethylene terephthalate)(PET) film was exposed to oxygen plasma glow discharge to produce peroxides on its surfaces. These peroxides were then used as catalysts for the polymerization of acrylic acid (AA) in order to prepare a carboxylic acid group-introduced PET (PET-AA). Insulin and heparin co-immobilized PET (PET-I-H) was prepared by the grafting of poly(ethylene oxide) (PEO) on to PET-AA, followed by reaction first with insulin and then heparin. These surface-modified PETs were characterized by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, electron spectroscopy for chemical analysis (ESCA), and a contact angle goniometer. The concentration of the heparin (1.23 microg/cm2) bound to the PEO-grafted PET (PET-PEO) was higher than that (0.77 microg/cm2) on the insulin-immobilized PET (PET-In). The blood compatibilities of the surface-modified PETs were examined using in vitro thrombus formation, plasma recalcification time (PRT), activated partial thromboplastin time (APTT), and platelet adhesion and activation. In the experiment with plasma proteins, the PRT and APTT were significantly prolonged for both the heparin-immobilized PET (PET-He) and the PET-I-H, suggesting the binding of immobilized heparin to antithrombin III. The percentage of platelet adhesion slightly increased with the introduction of AA on the PET surfaces, decreased with the introduction of PEO and insulin, and decreased further with the immobilization of heparin. The release of serotonin was highly suppressed on PET-He and PET-I-H, and on surface-modified PETs the percentage of its release increased with an increase in platelet adhesion.

Acrylates↗
PubMed2000

beta-Chitin-based wound dressing containing silver sulfurdiazine.

Physical and biological properties of some wound dressing materials based on beta-chitin were studied. Water vapor transmission rates (WVTR), oxygen permeabilities and biodegradation kinetics were examined for film-type samples. WVTR of samples was in the range 2400-2800 g/m2/day. However, oxygen permeabilities of the samples were relatively low. To improve oxygen permeabilities, porous sponge-type wound dressing materials were prepared. In addition, these sponge-type samples contained antimicrobial agents, silver sulfadiazine (AgSD), in order to prevent bacteria infection on a wound surface. Anti-microbacterial tests on agar plate were carried out to confirm the bactericidal capacity of present materials. These materials impregnating AgSD had the complete bactericidal capacity against pseudomonas aeruginosa up to 7 days. Finally, a wound healing effect of beta-chitin-based semi-interpenetrating polymer networks was evaluated from the animal test using the wistar rat in vivo. Histological studies confirm the proliferation of fibroblasts in the wound bed and a distinct reduction in infectious cells.

Journal Article↗
PubMed2000

Protective role of nitric oxide-mediated inflammatory response against lipid peroxidation in ultraviolet B-irradiated skin.

Ultraviolet (UV) irradiation is known to induce serious oxidative damage in the skin via lipid peroxidation. Nitric oxide (NO) synthesized by keratinocytes, melanocytes and endothelial cells in response to proinflammatory cytokines and UV radiation, has been reported to prevent UV-induced apoptosis in the skin. We have examined the effects of NO on UVB-induced lipid peroxidation in murine skin in vivo. UVB induced a dose-dependent increase in lipid peroxidation of skin extracts in vitro; however, lipid peroxidation in the skin in vivo remained unaffected at irradiation doses of less than 1.0 J cm-2 and decreased significantly at doses over 1.5 J cm-2 (P < 0.01). Time-delayed inhibition of lipid peroxidation in the skin in vivo was observed after irradiation at 1.5 J cm-2. Administration of N G-nitro-L-arginine methyl ester (L-NAME), an inhibitor of NO synthesis, enhanced lipid peroxidation (P < 0.05), while it suppressed the ear-swelling response (ESR), a biological marker of inflammation. By contrast, administration of sodium nitroprusside, an NO enhancer, suppressed lipid peroxidation (P < 0. 01), while it enhanced the ESR. Expression of inducible nitric oxide synthase (iNOS) was observed from 12 to 48 h postirradiation at doses of 0.4-1.6 J cm-2. The UVB-induced iNOS expression was markedly inhibited by L-NAME, suggesting that iNOS is a major enzyme in the production of NO. These results suggest that NO acts as a mediator of the inflammatory response in UVB-irradiated skin, and that lipid peroxidation is inversely regulated with the NO-mediated inflammatory response in vivo.

Animals↗
PubMed1999

Synthesis and characterization of heparinized polyurethanes using plasma glow discharge.

Polyurethanes (PU) were synthesized from 4,4'-diphenylmethane diisocyanate and polytetramethylene glycol, and subsequently with ethylene diamine as a chain extender. The PU film was exposed to oxygen plasma glow discharge to produce peroxides on the surfaces. These peroxides were then used as catalysts for the copolymerization of acrylic acid (AA) and methyl acrylate (MA) in order to prepare carboxyl group-introduced PU (PU-C). Heparin-immobilized PU was prepared using the coupling reaction of PU-C with polyethylene oxide (PEO) followed by the reaction of grafted PEO with heparin. The surface-modified PUs were then characterized by attenuated total reflection Fourier transform infrared spectroscopy, electron spectroscopy for chemical analysis (ESCA), and a contact angle goniometer. The concentration of carboxylic acid groups on the PU surfaces could be controlled within the range of 0.47-1.68 micromol cm(-2) by the copolymerization of AA and MA. The amounts of heparin coupled to terminus amino groups on PU-6 and PU-33 were 1.30 and 1.16 microg cm(-2), respectively. The water contact angle of the PU was decreased by AA grafting, and further decreased by PEO grafting and heparin immobilization, showing an increased hydrophilicity of the modified PUs. A 3% loss from the originally bound heparin appeared within several hours and thereafter almost no heparin was released when heparin-immobilized PUs were immersed in a physiological solution for 100 h, indicating the covalent immobilization of heparin on the surfaces.

Biocompatible Materials↗
PubMed1997

In vitro blood compatibility of functional group-grafted and heparin-immobilized polyurethanes prepared by plasma glow discharge.

Blood compatibilities of functional group-grafted and heparin-immobilized polyurethanes (PUs) were investigated using in vitro thrombus formation, plasma recalcification time (PRT), activated partial thromboplastin time (APTT), platelet adhesion and activation, and peripheral blood mononuclear cell (PBMC) activation. In the experiment with plasma proteins, PRT was shortened on amine group-grafted PU (PU-NH2) but prolonged on heparin-immobilized polyurethane (PU-Hep) when compared to PU control. APTT was significantly prolonged on PU-Hep, suggesting the binding of immobilized heparin to antithrombin III. The percentage of platelet adhesion was slightly increased by the introduction of functional groups such as carboxylic acid and primary amine on PU surfaces, but significantly decreased by the immobilization of heparin on the same substrate. The percentage of serotonin released from platelets adhered on surface-modified PUs was increased with increase of platelet adhesion. In the PBMC experiment, cells adhered less on heparin-immobilized PUs than on functional group-grafted PUs, and the production levels of tumour necrosis factor mRNAs from the cells stimulated by heparin-immobilized PU (PU-N-Hep) were smaller than those by the other substrates.

Amines↗
PubMed1996

Preparation and surface characterization of functional group-grafted and heparin-immobilized polyurethanes by plasma glow discharge.

Functional group-grafted polyurethanes were prepared by oxygen plasma discharge treatment, followed by graft polymerization of 1-acryloylbenzotriazole (AB) and a subsequent substitution reaction of AB with sodium hydroxide and ethylene diamine. The primary amine or carboxylic acid groups grafted on the surfaces were coupled with heparin using water-soluble carbodiimide. The modified surfaces were characterized by measuring the water contact angle, electron spectroscopy for chemical analysis and attenuated total reflection Fourier-transform infrared spectroscopy. The amount of heparin covalently immobilized on the primary amine- and carboxylic acid group-grafted polyurethanes were 2.0 and 1.4 micrograms cm-2, respectively, as determined by the toluidine blue method. The water contact angle of the polyurethanes was decreased by AB grafting, and further decreased by the introduction of functional groups such as carboxylic acid and primary amine and immobilization of heparin, showing increased hydrophilicity of the modified surfaces. Heparin was almost not released from the immobilized surfaces in the physiological solution for 100 h, indicating good stability of immobilized heparin.

Amines↗
PubMed1996

Vitiligo coexistent with nevus depigmentosus.

A 45-year-old Korean man had two distinct types of hypopigmented lesions on the forehead and back: vitiligo and nevus depigmentosus (ND). The hypopigmented macules on the forehead were incidentally discovered 15 days previously and responded well to steroid therapy. The hypopigmented macule on the back had been present since birth, was stable in size, and showed no response to steroid therapy. There were no remarkable differences between the two lesions in routine histopathology or Fontana-Masson staining. However, the lesion on the back was shown to contain melanocytes in electron microscopy (EM).

Humans↗
PubMed1995

The subgingival microflora and gingival crevicular fluid cytokines in refractory periodontitis.

Refractory periodontitis manifests as a rapid, unrelenting, progressive loss of attachment despite the type and frequency of therapy. This study examined possible relationships between cytokine levels in gingival crevicular fluid (GCF), occurrence of specific periodontopathic microflora, and disease activity in patients with refractory periodontitis. Refractory periodontitis patients (7 male and 3 female) were selected on the basis of history and longitudinal clinical observations. In each patient, 2 teeth with pocket depths greater than 6 mm were selected and individual acrylic stents were fabricated with reference grooves for each site. The sites were examined at both baseline and 3 months later. The pattern and amount of alveolar bone resorption were assayed by quantitative digital subtraction radiography. Pocket depth and attachment loss were measured with a Florida Probe. The gingival index was measured at 4 sites around each sample tooth. Sites were divided into active sites (> or = 2.1 mm loss of attachment in 3 months) or inactive sites (< or = 2.0 mm loss of attachment in 3 months). The distribution and prevalence of the predominant microflora in active and inactive sites were compared using anaerobic culture and indirect immunofluorescence. Interleukin-1 beta, 2, 4, 6 and tumor necrosis factor-alpha (TNF-alpha) levels in gingival crevicular fluid (GCF) were quantified by ELISA. Prevotella intermedia and Eikenella corrodens significantly decreased in inactive sites but remained the same in active sites after 3 months. The active sites revealed significantly higher GCF levels of IL-2 and IL-6 than inactive sites at both baseline and at 3 months. IL-1 beta was also significantly greater in active sites than in inactive sites at 3 months. Alveolar bone loss in active sites correlated with increased GCF levels of IL-1 beta and IL-2. These results suggest that GCF levels of IL-1 beta, IL-2 and IL-6 and P. intermedia and E. corrodens in subgingival plaque may serve as possible indicators of disease activity in refractory periodontitis.

Adult↗
PubMed1994

Cell behaviour on polymer surfaces with different functional groups.

Surfaces with differently chargeable functional groups were prepared on low density polyethylene sheets by corona discharge treatment, followed by graft copolymerization of acrylic acid (-COOH, negatively chargeable) and a subsequent substitution reaction of carboxylic acid groups to hydroxyl (-CH2OH, neutral) or amide (-CONH2, neutral) groups. The amide groups grafted on the surface were further converted to amine groups (-CH2NH2, positively chargeable). The prepared surfaces were characterized by measuring the water contact angle, electron spectroscopy for chemical analysis and Fourier-transform infrared spectroscopy in the attenuated total reflectance mode. It was observed that the wettability of the different functional group-grafted surfaces largely increases compared with the control surface but is not much affected by the kind of functional groups grafted. The interaction of Chinese hamster ovary cells with the functional group-grafted surfaces was investigated. The cells adhered and grown on the surfaces were counted using an electronic cell counter and observed by a scanning electron microscope. The surface grafted with amine groups was best for cell adhesion, spreading and growth probably owing to the positively chargeable character in aqueous cell culture medium. For surfaces grafted with neutral functional groups, the surface grafted with hydroxyl groups showed better cell spreading than that grafted with amide groups.

Alcohols↗
PubMed1994

N-terminal amino acid sequence of persimmon fruit beta-galactosidase.

beta-Galactosidase (EC 3.2.1.23) from persimmon fruit was purified 114-fold with a 15% yield using Sephadex G-100 gel filtration, CM-Sephadex ion exchange, and Sephacryl S-200 gel filtration chromatography, with subsequent electroelution from nondenaturing polyacrylamide gel electrophoresis (PAGE) gels. The estimated molecular mass of the native beta-galactosidase by Sephacryl S-200 was 118 kD. After sodium dodecyl sulfate-PAGE of the enzyme electroeluted from native gels, two subunits with estimated molecular masses of 34 and 44 kD were observed, suggesting that the native enzyme was an aggregate of several subunits. Amino acid composition and N-terminal amino acid sequences of the two major subunits were different.

Amino Acid Sequence↗
PubMed1993

Immobilization of proteins on poly(methyl methacrylate) films.

Polymethyl methacrylate (PMMA) films were treated by oxygen plasma discharge followed by acrylic acid (AA) grafting. The amount of carboxyl groups introduced by the grafting of AA on to the film surfaces was in the range 0.47-9.48 mumol/cm2, depending on the pressure of the plasma chamber during the discharge treatment. The carboxyl groups of the PMMA film surface previously activated with water soluble carbodiimide were coupled with bovine serum albumin, collagen and gelatin. The protein immobilization on the surface was confirmed by attenuated total reflection Fourier transform infra-red spectroscopy (ATR-FTIR) and electron spectroscopy for chemical analysis (ESCA). The amount of albumin, collagen and gelatin immobilized on the PMMA surface was 6.25, 7.25 and 13.75 micrograms/cm2, respectively, as determined by the coomassie brilliant blue-protein interaction. The water contact angle of the PMMA film was markedly decreased by oxygen plasma treatment, AA grafting or protein immobilization, indicating the increase of hydrophilicity of the surface-modified PMMA films. The protein-immobilized PMMA films may be widely used as a biocompatible material.

Biocompatible Materials↗
PubMed1989

Attachment and growth of fibroblast cells on polypeptide derivatives.

Attachment and growth of mouse fibroblast cells on polypeptide derivatives with different wettabilities were studied in the presence or absence of serum proteins. In the presence of serum, a peak level of cell attachment was observed for substrates with a contact angle of around 70 degrees. However, no relationship was found between cell attachment and water contact angle of the substrate in the absence of serum. Ca2+ -dependent cell attachment was observed on hydrophobic polypeptides in the absence of serum proteins. This suggests that Ca2+ -dependent membrane proteins function as mediators for cell attachment to hydrophobic polypeptides. In the presence of serum proteins, it was found that cell attachment is affected by the metabolism, Ca2+, and the cytoskeleton of the cell. Cell growth rate on hydrophilic polypeptide substrates was higher than that on intermediate or hydrophobic polypeptide substrates. This demonstrates that the strong interaction between cells and substrates will be unfavorable for a dewebbing process during mitosis.

Animals↗