• Journal of Life Science
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• v.18 no.7
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• pp.952-957
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• 2008

We evaluated the effects of various factors (e.g., serum, inhibitors of protein synthesis, and cytoskeleton and protein kinases) on early PMA-induced THP-1 cell adhesion using an adhesion assay with Sulforhodamine B (SRB) staining, which was used to assess the proliferation of the attached cells. THP-1 cell adhesion to a plastic substrate was detected 1 hr after exposure to Phorbol 12-Myristate 13-Acetate (PMA) and peaked after 18 hr. At concentrations > 25 nM PMA, the level of adhesion did not change. Based on our preliminary results, we used 25 nM PMA and 5 hr of culture as standard assay conditions. Early PMA-induced cell adhesion was not affected by the presence of serum or PD 98059 in the culture medium, but was affected by the addition of PKC inhibitors and cycloheximide. In the presence of actin inhibitor with PMA, the cell adhesion increased when comparing with PMA treatment only. Thus, early PMA-induced adhesion of THP-1 cells does not require serum in the culture medium, MAP-kinase activation, or actin polymerization, but does require de novo protein synthesis and PKC activation. Our SRB-based cell adhesion assay may be used to screen other PKC inhibitors.

• Polymer(Korea)
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• v.34 no.3
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• pp.274-281
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• 2010

In this study, PEG-PLA(or PLGA) amphiphilic di-block copolymers were synthesized by ring opening polymerization of D,L-lactide(or glycolide) and applied to polymeric micelle system for solubilization of a rosiglitazone as diabetes drug. The drug could be efficiently loaded into the polymer micelle by solid dispersion technique, and the drug-loaded micelles were characterized and evaluated as a drug delivery carrier by fluorescence spectrometer, DSC, and DLS measurements. The colloidal stability of drug loaded micelles in aqueous media could be enhanced by addition of 2-hydroxy-N-picolylnitinamide as a hydrotropic agent. The polymer micelles also showed biocompatible and nontoxic properties in vitro cell viability using MTT assay, and the drug loaded micelles were observed to be more effective than free drug for decreasing glucose in blood of rats.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.634-643
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• 2020

In this study, the rheological and tribological properties of urea grease were studied according to the type and amount of polytetrafluoroethylene (PTFE) powders added to the urea grease, which is the most widely used among solid lubricants, to develop an optimal lubrication system. Urea grease was synthesized using 4,4'-methylenebis(phenyl isocyanate)(MDI), oleylamine, and cyclohexylamine, and PTFE powders prepared by dispersion or suspension polymerization process were then added. The basic rheological and tribological properties of the prepared greases were compared. The worked penetration numbers of urea grease decreased with increasing amount of PTFE powders, but both PTFE powders caused no significant changes in heat resistance and copper corrosion resistance. The shear viscosity increased with increasing PTFE powder content, and the dispersion-type PTFE powder was more effective in increasing the viscosity. In the value of the loss coefficient = 1, the shear stress was higher for the grease containing PTFE powders than the non-PTFE added grease, and the dispersion-type PTFE-added grease showed higher viscosity than the suspension-type PTFE-added grease. Finally, urea grease was found to have a low-performance improvement in terms of wear reduction effects by adding PTFE powders, but the load-bearing performance was up to 2.5 times higher for the dispersion-type PTFE and five times higher for the suspension-type PTFE.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.3
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• pp.315-322
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• 2014

Purpose: The physical and optical characteristics of hydrophilic tinted contact lens containing titanium silicon oxide nanoparticles and the basic hydrogel contact lens material containing 4-iodoaniline were examined. In this study, the utility of titanium silicon oxide nanoparticles as a UV-blocking material for ophthalmologic devices were investigated by measuring the UV transmittance of the produced polymer. Also, titanium silicon oxide nanoparticles only without the addition of 4-iodoaniline in primary contact lens materials by copolymerizing two groups were compared. Methods: For manufacturing hydrogel lens, HEMA, MA, MMA, 4-iodoaniline and a cross-linker EGDMA were copolymerized in the presence of AIBN as an initiator. Also, the titanium silicon oxide nanoparticles was used as additive. After polymerization the physical properties such as water content, refractive index, contact angle and spectral transmittance of produced contact lenses were measured. Results: Measurement of the physical properties of the copolymerized material showed that the water content, refractive index, UV-B transmittance and contact angle were in the range of 35.01~38.60%, 1.4350~1.4418, $34.15{\sim}57.25^{\circ}$ and 1.0~10.0%, respectively. Titanium silicon oxide nanoparticles is not used as an additive in the experimental group, the results of the measurement showed that the water content, refractive index, contan angle and UV-B transmittance of the hydrogel lens polymer was 34.00~36.80%, 1.4378~1.4420, $40.15{\sim}60.16^{\circ}$ and 1.8~25.0%, respectively. Conclusions: Also, the transmittance for UV light was reduced significantly in combinations containing titanium oxide nanoparticles.

• Journal of Adhesion and Interface
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• v.18 no.3
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• pp.109-117
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• 2017

Poly(N-vinyl carbazole) (PVK) homopolymer, poly(4-vinylpyridine) (PVP) homopolymer, and PVK-b-PVP block copolymer were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization and the polymers were used to prepare non-aqueous graphene dispersions with four different solvents, ethanol, N-methyl-2-pyrrolidone (NMP), dichloromethane (DCM), and tetrahydrofuran (THF). $^1H-$ and $^{13}C-NMR$ spectroscopy, size exclusion chromatography (SEC), and differential scanning calorimetry (DSC) were carried out to confirm the chemical structure of the polymers. Stability of graphene dispersions was measured by on-line turbidity measurement. Time-dependent Turbiscan Stability Index (TSI) values were interpreted in terms of surface tension (${\sigma}$) and solubility parameter (${\delta}$) among solvents, polymers, and graphene. It was confirmed that the solubilities of polymer and surface tension between solvent and graphene affected the dispersion stability of graphene. PVK-b-PVP block copolymer could effectively maintain the low TSI values of graphene dispersions in ethanol and THF, which have been known as poor solvents for graphene dispersions. It can also be noted that DCM shows good dispersion stability comparable to NMP, which has been known as the best solvent for graphene dispersion.

• Polymer(Korea)
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• v.31 no.6
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• pp.518-525
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• 2007

The thermomechanical properties and morphologies of nanocomposite fibers of poly(ethylene terephthalate)(PET) incorporating thermally stable organoclays are compared. Dodecyltriphenyl-phosphonium-mica($C_{12}PPh-Mica$) and 1-hexadecane benzimidazole-mica ($C_{16}BIMD-Mica$) were used as reinforcing fillers in the fabrication of PET hybrid fibers. Dispersions of organoclays with PET were studied by using the in-situ polymerization method at various organoclay contents to produce nano-scale composites. The thermo-mechanical properties and morphologies of the PET hybrid fibers were determined using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), wide angle X-ray diffraction (XRD), electron microscopy (SEM and TEM), and a universal tensile machine (UTM). Transmission electron microscopy (TEM) micrographs show that some of the clay layers are dispersed homogeneously within the polymer matrix on the nano-scale, although some clay particles are agglomerated. We also found that the addition of only a small amount of organoclay is enough to improve the thermal stabilities and mechanical properties of the PET nanocomposite fibers. Even polymers with low organoclay content (<5 wt%) were found to exhibit much higher thermo-mechanical values than pure PET fibers.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.21
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• pp.9319-9325
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• 2014

Alkaloids are the most extensively featured compounds of natural anti-tumor herbs, which have attracted much attention in pharmaceutical research. In our previous studies, a mixture of major three alkaloid components (5, 6-dihydrobicolorine, 7-deoxy-trans-dihydronarciclasine, littoraline) from Hymenocallis littoralis were extracted, analyzed and designated as AHL. In this paper, AHL extracts were added to human liver hepatocellular cells HepG-2, human gastric cancer cell SGC-7901, human breast adenocarcinoma cell MCF-7 and human umbilical vein endothelial cell EVC-304, to screen one or more AHL-sensitive tumor cell. Among these cells, HepG-2 was the most sensitive to AHL treatment, a very low dose ($0.8{\mu}g/ml$) significantly inhibiting proliferation. The non-tumor cell EVC-304, however, was not apparently affected. Effect of AHL on HepG-2 cells was then explored. We found that the AHL could cause HepG-2 cycle arrest at G2/M checkpoint, induce apoptosis, and interrupt polymerization of microtubules. In addition, expression of two cell cycle-regulated proteins, CyclinB1 and CDK1, was up-regulated upon AHL treatment. Up-regulation of the Fas, Fas ligand, Caspase-8 and Caspase-3 was observed as well, which might imply roles for the Fas/FsaL signaling pathway in the AHL-induced apoptosis of HepG-2 cells.

• Journal of Life Science
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• v.27 no.6
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• pp.632-639
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• 2017

Mature haptoglobin (Hp) is a plasma glycoprotein and acts as an antioxidant by scavenging cell-free hemoglobin (Hb). Prohaptoglobin (proHp) is an unprocessed Hp precursor which is present a little in circulation. However, the biological function of proHp remains unknown. To investigate the structural and functional differences between proHp and Hp, we prepared recombinant proHp isoforms and compared their sialic acid content and Hb-binding capacity with those of mature isoforms. When proHp samples were analyzed by Western blot under non-reducing conditions, proHp1 was detected as one band of approximately 130 kDa and proHp2 as multiple bands >200 kDa, in the manner of mature Hp1-1 and Hp2-2, respectively. On the native polyacrylamide gel under non-reducing and non-denaturing conditions, both proHp isoforms migrated more slowly than their mature Hp counterparts. In addition, the lectin-based ELISA assay demonstrated that the content of sialic acid in proHp1 and proHp2 was much less than in Hp1-1 and Hp2-2. The Hb-binding capacity of proHp was also lower than those of mature Hp. These findings indicate that proHp and Hp are similar in the size and polymerization pattern, but different in sialic acid content and Hb-binding activity. It suggests precursor proHp may exert different functions in circulation than does mature Hp.

• Journal of the Korean Chemical Society
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• v.41 no.7
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• pp.337-342
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• 1997

Acryloylmethylbenzo-15-crown-5 was prepared from the reaction of 4'-hydroxymethylbenzo-15-crown-5 with acryloyl chloride. And, poly(acryloylmethylbenzo-15-crown-5) [poly(AMB15C5)] was synthesized by radical polymerization using AIBN as initiator in benzene. Coated wire lead(II) ion-selective electrodes ($Pb^{2+}$-CWISEs) using either poly(AMB15C5) or B15C5 as neutral carrier were prepared, respectively. $Pb^{2+}$-CWISEs gave linear responses with slopes of 28$\pm$ 1mV per decade within the concentration range of $10^{-5} M{\sim}10^{-1}$ M, respectively. Also, the detection limits were $10^{-6}$ M and response times were either 3 or 5 min. for B15C5 and poly(AMB15C5), respectively. $Pb^{2+}$-CWISE base on B15C5 was rather unstable than poly(AMB15C5)'s due to solubility of the B15C5 in water. The selectivity coefficients of a variety of interfering ions such as $Mg^{2+},\; Ca^{2+},\; Co^{2+},\; Ni^{2+},\; Cu^{2+},\; Zn^{2+}$ and $Cd^{2+}$ were small ($10^{-4}{\sim}10^{-5}$), while those of $Na^+$ and $K^+$ were large (0.1∼0.01). In addition, the electrode responses depended upon the pH of test solution and the composition of the membrane. In the range pH 3∼6 of test solution, potentials of Pb2+-CWISEs were hardly changed. The optimal contents of B15C5 and poly(AMB15C5) were 7.7 wt% and 13.1 wt%, respectively.

• Applied Chemistry for Engineering
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• v.5 no.3
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• pp.395-405
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• 1994

The various functional groups, such as hydroxyl(-OH), carboxyl(-COOH) and quinonic oxygen(OC<) on the carbon black(abbreviated to CB) surface were activated with n-butyl lithium solution in n-hexane and then acrylate and methacrylate monomers were graft polymerized onto these activated anionic sites and CB-grafted polymers were obtained. To separate homopolymers from reaction mixture, non-solvent precipitation method or centrifugal separating method were applied. Subsequently, conversion, grafting ratio and efficiency were determined at various reaction temperatures and times. In case of acrylates, the grafting ratio showed 20~30% but methacrylates showed 150~200%. Also the anion polymerizations between CB and monomers were nearly reached to equilibrium state within one or two hours under each reaction temperatures but conversion and grafting ratio were increased a little with reaction temperature increase. In colloidal dispersion stability test, before heat-drying, the all CB-grafted polymers showed good dispersed stability in good solvents for acrylic and methacrylic homopolymers. Futhermore, CB-polymethacrylates were found to show excellent collidal properties for good solvents of methacrylic homopolymer even after heat-drying. Identification of the grafted polyacrylates and polymethacrylates onto the CB surface was performed by FT-IR spectroscopy. In addition, electric resistance values of CB-grafted polymers were measured by Four-probe method, and the increase of the grafting ratio showed the increase of the surface resistance.