• Journal of Microbiology and Biotechnology
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• v.30 no.12
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• pp.1827-1834
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• 2020

Candida albicans is a major fungal pathogen in humans. In our previous study, we reported that an ethanol extract from Aucklandia lappa weakens C. albicans cell wall by inhibiting synthesis or assembly of both (1,3)-β-D-glucan polymers and chitin. In the current study, we found that the extract is involved in permeabilization of C. albicans cell membranes. While uptake of ethidium bromide (EtBr) was 3.0% in control cells, it increased to 7.4% for 30 min in the presence of the A. lappa ethanol extract at its minimal inhibitory concentration (MIC), 0.78 mg/ml, compared to uptake by heat-killed cells. Besides, leakage of DNA and proteins was observed in A. lappa-treated C. albicans cells. The increased uptake of EtBr and leakage of cellular materials suggest that A. lappa ethanol extract induced functional changes in C. albicans cell membranes. Incorporation of diphenylhexatriene (DPH) into membranes in the A. lappa-treated C. albicans cells at its MIC decreased to 84.8%, after 60 min of incubation, compared with that of the controls, indicate that there was a change in membrane dynamics. Moreover, the anticandidal effect of the A. lappa ethanol extract was enhanced at a growth temperature of 40℃ compared to that at 35℃. The above data suggest that the antifungal activity of the A. lappa ethanol extract against C. albicans is associated with synergistic action of membrane permeabilization due to changes in membrane dynamics and cell wall damage caused by reduced formation of (1,3)-β-D-glucan and chitin.

• Membrane Journal
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• v.33 no.6
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• pp.279-304
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• 2023

Polybenzimidazole (PBI) based membranes have evolved in literature as a popular membrane material for various applications in the past two decades because of their high temperature thermal durability, strong mechanical and tensile properties, high glass transition temperature (T_g), ion conduction ability at elevated temperature (up to 200℃), oxidative or chemical durability along with robust network like structural rigidity, which make PBI membranes suitable for various potential applications in chemically challenging environments. Ion conducting PBI based membranes have been extensively utilized in high temperature proton exchange membrane fuel cells (HT-PEMFC). In addition, PBI based membranes have been vastly utilized for the development of gas separation membranes and organic solvent nanofiltration (OSN) membranes for their unique characteristics. This review will cover the recent progress and application of various types of flat sheet PBI based membranes for HT-PEMFC, gas separation and OSN application.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.282-285
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• 2009

This study presents preparation and characterization of composite membranes based on ionic liquids. The ionic liquids act as water in sulfonated membranes. On the behalf of ionic conduction through ionic liquid inside the membranes, non-aqueous membranes showed Arrenhius dependence on temperature with no external humidification. It was implied that hopping mechanism of proton was dominant in the ionic liquid based membranes. In addition, small angle X-ray (SAXS) studies provided the information on morphology of ionic clusters formed by the interaction between sulfonic acid groups of the polymers and ionic liquids. The SAXS spectra showed matrix peaks, ionomer peaks and Prodo's law for Nafion based composite membranes and only matrix peaks for hydrocarbon based ones. However, ionic conductivity and atomic force microscopy (AFM) images showed the clear formation of ionic clusters of the hydrocarbon based composite membranes. It implies for ionic liquid based high temperature membranes that it is important to use sulfonated polymers as solid matrix of ionic liquid which can form clear ionic clusters in SAXS spectra.

• Carbon letters
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• v.13 no.3
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• pp.139-150
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• 2012

Poly-L-lactic acid (PLLA), PLLA/hydroxyapatite (HA), PLLA/multiwalled carbon nanotubes (MWNTs)/HA, PLLA/trifluoroethanol (TFE), PLLA/gelatin, and carbon nanofibers (CNFs)/${\beta}$-tricalcium phosphate (${\beta}$-TCP) composite membranes (scaffolds) were fabricated by electrospinning and their morphologies, and mechanical properties were characterized for use in bone tissue regeneration/guided tissue regeneration. MWNTs and HA nanoparticles were well distributed in the membranes and the degradation characteristics were improved. PLLA/MWNTs/HA membranes enhanced the adhesion and proliferation of periodontal ligament cells (PDLCs) by 30% and inhibited the adhesion of gingival epithelial cells by 30%. Osteoblast-like MG-63 cells on the randomly fiber oriented PLLA/TEF membrane showed irregular forms, while the cells exhibited shuttle-like shapes on the parallel fiber oriented membrane. Classical supersaturated simulated body fluids were modified by $CO_2$ bubbling and applied to promote the biomineralization of the PLLA/gelatin membrane; this resulted in predictions of bone bonding bioactivity of the substrates. The ${\beta}$-TCP membranes exhibit good biocompatibility, have an effect on PDLC growth comparable to that of pure CNF membrane, and can be applied as scaffolds for bone tissue regeneration.

• Membrane Journal
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• v.12 no.1
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• pp.51-53
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• 2002

The hydrogen ions in poly (vinyl alcohol) (PVA)/sulfosuccinic acid (SSA) membranes substiuted with $Li^+, Na^+, and K^+/ $of monvoalent metal ions, $Mg^{2+}, Ca^{2+} and Ba^{2+}$ of divalent metal ions, and $Al^{3+}$ of trivalent metal ion. In addition, $Li^+ ions were exchanged with varing reaction time. The effects of metal ions exchanged were investigated in terms of methanol permeability -uling diffusion cell. The methanol permeabilies decreased in the sequence of $Na^+, Li^+ and K^+$ and this might be due to the 'Salting-out' effect while the methanol permeabilities for divalent and trivalent ion-substituted membranes were affected by the combined effects of salting-out, eletrostatic crosslinking and extent of metal ion substiution. As for $Li^+$ ions, methanol permeabilities of PVA/SSA membranes decreased in proportion to the degrees of subsituted $Li^+$ ions.

• Journal of the Korean Electrochemical Society
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• v.11 no.1
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• pp.1-5
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• 2008

A Pt-layer was deposited on the anode side of a Nafion membrane via a sputtering method in order to reduce methanol crossover in a direct methanol fuel cell (DMFC). The methanol permeation and the proton conductivity through the modified membranes were investigated. The performances of the direct methanol fuel cell were also tested using single cells with a Nafion membrane and the modified membranes. The Pt-layers on the membrane blocked both methanol crossover and proton transport through the membranes. Methanol permeability and proton conductivity decreased with an increase of the platinum layer thickness. At methanol concentration of 2 M, the DMFC employing the modified membrane with a platinum layer of 66 nm-thickness showed similar performance to that of a DMFC with a bare Nafion membrane in spite of the lower proton conductivity of the former. The maximum power density of the cell using the modified membrane with a platinum layer of 66 nm-thickness increased slightly while that of the cell with the bare membrane decreased abruptly when a methanol solution of 6M was supplied.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.184-184
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• 2006

We have succeeded in the preparation of high molecular weight polybenzimidazoles by solution polycondensation of 3,3'-diaminobenzidine tetrahydrochloride with isophthalic acid, terephthalic acid, or with their derivatives using polyphosphoric acid both as solvent and as condensing agent. Also, we modified phosphoric acid into fluoroalkyl-phosphonic acids[F-PA]. The main reasons are as follows, first of all F-PAs are stronger acids than PA and alkylphosphonic acids which should promote proton hopping and transport. In addition, F-PA has weaker adsorption onto Pt which help to prevent electrocatalyst poisoning and promote higher oxygen reduction activity. The ionic conductivity of 85%-H3PO4 doped membranes show $10^{-2}\;Scm^{-1}\;to\;3{\times}10^{-2}\;Scm^{-1}\;at\;150^{\circ}C$ MEA with 2 %-added electrolyte shows slightly higher cell voltage than the others.

• Macromolecular Research
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• v.14 no.2
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• pp.214-219
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• 2006

Cast Nafion-based composite membranes containing different amounts of organic, nanorod-shaped polyrotaxane were prepared and characterized, with the aim of improving the properties of polymer electrolyte membranes for direct methanol fuel cell applications. Polyrotaxane was prepared using the inclusion-complex reaction between ${\alpha}$-cyclodextrin and poly(ethylene glycol) (PEG) of different molecular weights. The addition of polyrotaxane to Nafion changed the morphology and reduced the crystallinity. The conductivity of the composite membranes increased with increasing polyrotaxane content up to 5 wt%, but then decreased at higher polyrotaxane contents. Well-dispersed, organic polyrotaxane inside the membrane can provide a tortuous path for the transport of methanol, as the methanol permeability depends on the aspect ratio of polyrotaxane, which is controlled by the molecular weight of PEG. All of the Nafion-based, polyrotaxane composite membranes showed a higher selectivity parameter than the commercial Nafion films did.

• Textile Coloration and Finishing
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• v.7 no.3
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• pp.38-43
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• 1995

To improve the biofunctional properties of silk fibroin membranes, 2-(methacryloyloxy)ethyl-2-(trimethylammonium)ethyl phosphate(MTP), which is a methacrylate with phospholipid polar groups grafted and poly(MTP-co-BMA) was coated on the surface of silk fibroin membranes. The permeability and biocompatibility of silk fibroin membranes with phosphoryl choline group were investigated. The permeability of a salt(NaCl) was increased with grafting by MTP. Futhermore, the poly(MTP-co-BMA)-coated silk fibroin membranes displayed less blood cell adhesion than the silk fibroin membranes.

• Textile Coloration and Finishing
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• v.7 no.2
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• pp.63-69
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• 1995

To improve the blood compatibility of chitosan membranes, 2-(methacryloyloxy)-ethyl-2-(trimethylammonium)ethyl phosphate(MTP), which is a methacrylate with phospholipid polar groups, was grafted on the surface of chitosan membranes and the biocompatibility of MTP-grafted chitosan membranes was investigated. The permeation coefficient gradually decreased with increasing in molecular weights of biocomponents below 10$^{4}$, and drastically decreased above 10$^{4}$. This result corresponds with the permeability of solutes in case of hemodialysis membranes. The MTP-grafted chitosan membranes displayed less blood cell adhesion than the chitosan membranes. This may due to the formation of biomembrane4ike surface by adsorption and arrangement of phospholipid molecules from serum onto the MTP copolymer surface.