• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.05a
• /
• pp.6-10
• /
• 2001

We synthesized polypyrrole (PPy) nanotubules by oxidative polymerization of the pyrrole monomer on the pore of a polycarbonate membrane. The electrochemical behavior was investigated using cyclic voltammetry and AC impedance. The redox potential was about -0.5 V vs. Ag/AgCl reference electrode, while the potential was about 0 V for electro-synthesized PPy film. It is considered as the backbone grows according to the pore wall. Therefore, it is possible to be arranged regularly. That leads to improvement in the electron hopping. The AC impedance plot gave a hint of betterment of mass transport. PPy nanotubules have improved in mass transport, or diffusion. That is because the diffusion occurs through a thin pore wall of PPy nanotubules. The kinetic parameter of PPy nanotubules enzyme electrode with glucose solution was evaluated. The formal Michaelis constant and maximum current calculated by computer were about 23.8 mmol $dm^{-3}$ and $440\;{\mu}A$ respectively. Obviously, an affinity for the substrate and current response of the PPy nanotubules enzyme electrode are rather good, comparing with that of PPy film. What is more, the enzyme electrode is sensitive to blood sugar of a diabetic serum despite an obstruction of ascorbic acid, oxygen, some protein and/or hormone.

• Journal of Pharmaceutical Investigation
• /
• v.31 no.1
• /
• pp.43-47
• /
• 2001

Sterically stabilized liposomes (SSL) have been introduced for longer circulation in blood than conventional liposomes (CL). However, there are a couple of problems in SSL preparation due to the instability of phospholipid and the degradation of drug in aqueous conditions. To solve these problems, it is necessary to go through lyophilization process. Therefore, in this study, effects of lyophilization on SSL were evaluated for physical characteristics changes upon rehydration of lyophilized SSL such as the particle size, efficiency of drug entrapment, turbidity and drug release. SSL containing streptozocin, a water-soluble anticancer drug as a model compound, were prepared with DSPC and DSPE-PEG 2000. The size was controlled to 100 nm by extrusion with polycarbonate membrane, and sucrose was used as a cryoprotectant for lyophilization at the 1:3 (lipid:sucrose) ratio. Upon rehydration of lyophilized SSL, the average size was in the range of $50{\sim}200\;nm$ which is adequate for longer circulation in blood, and the encapsulation efficiency was kept as its initial state. Rehydrated SSL were not adsorbed to rat plasma protein and revealed a similar drug release profile to that of fresh SSL before lyophilization. Therefore, lyophilization could be introduced efficiently to overcome aqueous instability problems of SSL.

• Rapid Communication in Photoscience
• /
• v.2 no.3
• /
• pp.82-84
• /
• 2013

We fabricated dye-sensitized solar cells (DSSCs) with $TiO_2$ nanowire (NW)/nanoparticle (NP) composite and solidified nanogel as the photoelectrode and electrolyte, respectively. $TiO_2$ NWs were generated via pore-infiltration of titanium (IV) isopropoxide (TTIP) into a track-etched polycarbonate membrane with a pore diameter of 100 nm, followed by calcination at $500^{\circ}C$. Energy conversion efficiency of $TiO_2$ NW/NP-based DSSCs was always higher than that of NP-based cells. We attributed this to improved light scattering and electron transport by $TiO_2$ NWs, as verified by intensity modulation photocurrent spectroscopy (IMPS) and intensity modulation photovoltage spectroscopy (IMVS) analyses. Quasi-solid-state DSSCs with NW/NP composites exhibited 5.0% efficiency at 100 $mW/cm^2$, which was much greater than that of NP-based cells (3.2%).

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.11a
• /
• pp.247-250
• /
• 2009

This study considers the feasibility of using the low cost assembled separator. The graphite plate has been widely used as the separator in the field of PEMFCs(Polymer electrolyte membrane fuel cell) industry because of its excellent material properties such as good corrosion resistance, good electrical conductance and so on. However, there are some problems for the commercialization due to its poor cost effectiveness for the large volume manufacturing and lack of mechanical strength. From this respect, this study has focused on the manufacturing technology in order to reduce the price for the commercialization of separator. This study also shows that the assembled separator of the suggested structure, which is composed of grafoil and PC(PolyCarbonate) materials, could be manufactured at low cost enough for the mass production. The flow fields produced by cutting foils and the base plates of the separators were simply made by mechanical work.

• Korean Chemical Engineering Research
• /
• v.43 no.2
• /
• pp.236-242
• /
• 2005

Membrane fouling by protein mixtures during microfiltration has been investigated for binary mixtures of bovine serum albumin (BSA), casein, lysozyme, pepsin, and ovalbumin. Filtration experiments were carried out using $0.2{\mu}m$ polycarbonate track-etched (PCTE) membrane in a stirred cell under constant transmembrane pressure (14 kPa) and concentration of hydrogen ion (pH=11) to study the effect of mixture composition on filtrate flux decline. Flux decline data were analyzed using a pore blockage-cake formation model developed recently. It was found that the model is in a good agreement with the experimental data. Fouling parameters such as the rate of pore blockage(${\alpha}$), the initial resistance of the protein deposit ($R_{po}$) and the increasing rate of the protein layer resistance(${\beta}$) were used to evaluate the rate of filtrate flow by membrane fouling in the binary mixture system. Generally, the trend of ${\alpha}$ is comparable with that of filtrate flux decline. It was also found that fast flux decreasing was observed over the binary mixture containing casein. The result is due to high value of the initial resistance of the protein deposit ($R_{po}$) over casein.

• Journal of Korean Society for Atmospheric Environment
• /
• v.16 no.5
• /
• pp.453-467
• /
• 2000

The aim of this research is to collect and characterize fine particles (FPM:$\leq$2.5${\mu}{\textrm}{m}$) and coarse particles (CPM: 2.5~10${\mu}{\textrm}{m}$) using a low volume air sampler provided by the IAEA, at urban (Taejon) and rural area(Wonju) for a period of about two years(April 1996 to May 1998) and to promote a use of nuclear analytical techniques for air pollution studies. For the collection of airborne particulate matter (PM(sub)10), the Gent stacked filter unit sampler and polycarbonate membrane filters were employed. The concentration of trace elements in collected APM samples were determined byu instrumental Neutron Activation Analysis. For validation of the analytical data, internal quality control were implemented by using both the comparison of the analytical results of standard reference materials(NIST SRM 1648) and interlaboratory comparison for proficiency test (NAT-3). The standard uncertainty was less than 15% and Z-score of two samples were within $\pm$1. The monitoring of (PM(sub)10) mass concentration and elemental concentrations were carried out weekly. The average mass concentration of (PM(sub)10) in urban and rural areas were 59.2$\pm$36.5$\mu\textrm{g}$/㎥ and 41.4$\pm$23.7$\mu\textrm{g}$/㎥, respectively. To investigate the emission source, the enrichment factors were calculated for the fine and coarse particle fractions at two sites, respectively and these values were classified for anthropogenic and soil origin elements.

• Journal of Biomedical Engineering Research
• /
• v.28 no.3
• /
• pp.387-391
• /
• 2007

An oxygenator is a very important artificial organ and widely used for patients with lung failure or during open heart surgery. Although an oxygenator has been widely studied worldwide to enhance its efficiency, studies on oxygenators, in particular when using a pulsatile blood flow, are domestically limited. Therefore, a new oxygenator was developed in the lab and animal experimental results are described in the paper. The oxygenator is composed of polycarbonate housing and polypropylene hollow fibers. It has a total length of 400 mm and a surface area of $1.7 m^2$. The animal experiment lasted for 4 hours. The blood flow rate was set to 2 L/min and a pulsatile blood pump, T-PLS (Twin-Pulse Life Support), was used. Samples were drawn at the oxygenator's inlet and outlet. The total hemoglobin (Hb), saturation oxygen ($sO_2$), and partial oxygen pressure ($pO_2$), partial $CO_2$ pressure ($pCO_2$), and plasma bicarbonate ion concentration ($HCO_3^-$) were measured. The oxygen and carbon dioxide transfer rates were also calculated based on the experimental data in order to estimate the oxygenator's gas transfer efficiency. The oxygen and carbon dioxide transfer rates were $16.4{\pm}1.58$ and $165.7{\pm}10.96 mL/min$, respectively. The results showed a higher carbon dioxide transfer rate was achieved with the oxygenator. Also, the mean inlet and outlet blood pressures were 162.79 and 137.92 mmHg, respectively. The oxygenator has a low pressure drop between its inlet and outlet. The aim of own preliminary study was to make a new oxygenator and review its performance when applying a pulsatile blood pump thus, confirming the possibility of a new oxygenator suitable for pulsatile flow.

• Journal of Periodontal and Implant Science
• /
• v.25 no.2
• /
• pp.279-289
• /
• 1995

The most important object of periodontal treatment is the perfect regeneration of destructed periodontal tissue. The healing of periodontal lesion is affected by several cells & factors, which result in formation of long juntional epithelium, root resorption, bony ankylosis or connective tissue attachment. And ideal healing is enhanced by epithilial exclusion or periodontal ligament cell activation. In this investigation, I studied the effect of Zizyphus Fructus extract which enhances biologic activity& collagen synthesis, on the chemotaxis & cell nature. The cells were obtained from interdental area & middle third area of the freshly extracted teeth for the orthodontic purpose. And they were fully incubated in${\alpha}-MEM$ solution containing $100{\mu]g/ml$ penicillin & $100{\mu]g/ml$ streptomycin followed by 6 generation incubation. The test cells were collected by trypsin-EDTA & centrifuge in the fully incubated cells, counted by Hernacyotmeter, incbated $5{\times}10^5/ml$ cells for 24 hours, re-incubated 24 hours in media containing natural extract and photographed. The cells were incubated for 4 hours in 48 well microchemotaxis chamber bisecting upper & lower chamber by 8ug/m pore polycarbonate membrane coating 5mg/ml gelatin solution. The migrated cells in microscope were counted, which meaned cell chemotaxis activity. The study had shown that the morphology of cell was spindle-shaped as the control group, and the subextract test groups were not significantly different. In gingival fibroblasts, the chemotaxis effect of PDGF was statistically significant compared to control group. The Zizyphus Fructus extract was more or less enhanced chemotaxis effect and in $1{\mu}g/ml$ concentration the chemotaxis effect was slightly elevated compared with $10{\mu}g/ml$ concentration. But, among the subextracts, it was not significantly defferent. In PDL cells, the chemotaxis effect of PDGF in statistically significant, and the zizyphus Fructus extract had shown the enhanced effect. The effect was slightly higher in $1{\mu}g/ml$ concentration than 10g/ml concentration,and no significance among the subextracts.

• Korean Journal of Veterinary Research
• /
• v.33 no.4
• /
• pp.623-632
• /
• 1993

This study was conducted to develop a sensitized latex-antigen for serodiagnosis of toxoplasmosis in animals. Tachyzoites of T gondii(RH-strain) harvested from mouse peritoneal cavity were purified through the filtraton of polycarbonate membrane(pore size, $3.0{{\mu}m}$, Costar Co.) and disrupted by ultrasonicator. The tachyzoite suspension was ultracentrifuged for 30 min at $60,000{\times}g(4{^{\circ}C})$ and the supernatant was used as a water-lysate antigen. Polystyrene latex particles of $0.8{{\mu}m}$ in diameter(Sigma) were used for the preparation of sensitized latex-antigen suspension. The several parameters including the preparation conditions, incubation buffer. serum dilution buffer and stability of agglutination reactions were evaluated and the results obtained were summarized as follows : 1. The antigen consisting of a water-lysate of T gondii tachyzoites was adsorbed onto polystyrene latex particles of $0.8{{\mu}m}$ in diameter by adding a latex suspension to an equal volume of diluted antigen solution and by incubating the mixture at $37{^{\circ}C}$ under different conditions. 2. The optimum incubation buffer used for the antigen sensitization was 0.1M Tris-HCl buffer(pH 8.0). 3. The optimum serum dilution buffer used for the latex agglutination test was 0.1M Tris-HCl-NaCl buffer(pH 7.4) containing 300 mM NaCl. But 0.1M Tris-HCl-NaCl buffer(pH 7.4) containing 300-600 mM NaCl, 0.5% BSA and 0.01% Tween-20 improved the agglutination pattems and cleared the background of microplate well without the effects on L.A titer. 4. The time required for antigen sensitization was 40 and 60 min in incubation buffer(pH 8.0) at $37{^{\circ}C}$. But the optimun time for antigen sensitization was min at $37{^{\circ}C}$. 5. The optimun quantity of antigen absorbed on latex particles for proper agglutination was the range of 20 to $32{\mu}g$ of latex particles. 6. The optimun concentration of the latex-antigen suspension for the proper agglutination reaction was determined as 0.2%(w/v). 7. The specificity, rapidity and simplicity of the latex-particle agglutination test suggested that it might be adaptable to large scale serum screening.

• Tuberculosis and Respiratory Diseases
• /
• v.40 no.3
• /
• pp.236-249
• /
• 1993

Background: Among the injurious agents to which the lung airspaces are constantly exposed are reactive species of oxygen. It has been widely believed that reactive oxygen species may be implicated in the etiology of lung injuries. In order to elucidated how this oxidant causes lung cell injury, we investigated the effects of exogenous $H_2O_2$ on alveolar epithelial barrier characteristics. Methods: Rat type II alveolar epithelial cells were plated onto tissue culture-treated polycarbonate membrane filters. The resulting confluent monolayers on days 3 and 4 were mounted in a modified Ussing chamber and bathed on both sides with HEPES-buffered Ringer solution. The changes in short-circuit current (Isc) and monolayer resistance (R) in response to the exogenous hydroperoxide were measured. To determine the degree of cellular catalase participation in protection against $H_2O_2$ injury to the barrier, experiments were repeated in the presence of 20 mM aminotriazole (ATAZ, an inhibitor of catalase) in the same bathing fluid as the hydroperoxide. Results: These monolayers have a high transepithelial resistance (>2000 ohm-$cm^2$) and actively transport $Na^+$ from apical fluid. $H_2O_2$(0-100 mM) was then delivered to either apical or basolateral fluid. Resulting indicated that $H_2O_2$ decreased Isc and R gradually in dose-dependent manner. The effective concentration of apical $H_2O_2$ at which Isc (or R) was decreased by 50% at one hour ($ED_{50}$) was about 4 mM. However, basolateral $H_2O_2$ exposure led to $ED_{50}$ for Isc (and R) of about 0.04 mM. Inhibition of cellular catalase yielded $ED_{50}$ for Isc (and R) of about 0.4 mM when $H_2O_2$ was given apically, while $ED_{50}$ for basolateral exposure to $H_2O_2$ did not change in the presence of ATAZ. The rate of $H_2O_2$ consumption in apical and basolateral bathing fluids was the same, while cellualr catalase activity rose gradually with time in culture. Conclusion: Our data suggest that basolateral $H_2O_2$ may affect directly membrane component (e.g., $Na^+,\;K^+$-ATPase) located on the basolateral cell surface. Apical $H_2O_2$, on the other hand, may be largely degraded by catalase as it passes through the cells before reaching these membrane components. We conclude that alveolar epithelial barrier integrity as measured by Isc and R are compromised by $H_2O_2$ being relatively sensitive to basolateral (and insensitive to apical) $H_2O_2$.