Youngjin Choi

Effect of initial carbon sources on the performance of microbial fuel cells containing Proteus vulgaris.

Mediator-coupled microbial fuel cells containing Proteus vulgaris were constructed and the cell performance was tested. Fuel cell efficiency depended on the carbon source in the initial medium of the microorganism. Maltose and trehalose were not utilized substantially by P. vulgaris; however, their presence in the initial medium resulted in enhanced cell performance. In particular, galactose showed 63% coulombic efficiency in a biofuel cell after P. vulgaris was cultured in a trehalose-containing medium. This work demonstrates that optimum utilization of carbon sources by microorganisms, which leads to the maximization of fuel cell performance, is possible simply by adjusting initial carbon sources.

Effect of initial carbon sources on the electrochemical detection of glucose by Gluconobacter oxydans

An electrochemical system consisted of Gluconobacter oxydans as a microorganism and 2-hydroxy-1,4-naphthoquinone (HNQ) as a mediator has been setup to examine the effect of initial carbon sources on the detection of glucose. Catalytic current due to the oxidation of glucose was observed only when both G. oxydans and HNQ were present. From amperometric measurements, it was found that the sensitivity strongly depended on the initial carbon sources. The sensitivity was highest for the cells cultured in a fructose-containing medium and decreased in the order, mannitol > sucrose > glucose > galactose > glycerol. The difference in sensitivity was explained by considering the current rising pattern at an initial stage of a microbial fuel cell constructed with the same components. The rising time, not the fuel cell efficiency, could directly be related to the sensitivity order. A sensor where G. oxydans was confined at the vicinity of the electrode by the semipermeable membrane was constructed. A linear response over a millimolar range of glucose concentration was observed with a cell grown in galactose-containing medium. This work demonstrates that the initial carbon source play an important role on glucose sensoring and should be considered in a real application.

Solubility enhancement of a hydrophobic flavonoid, luteolin by the complexation with cyclosophoraoses isolated from Rhizobium meliloti

A plant flavone, luteolin is a well-known inducer of nod genes in the Rhizobium meliloti. Its poor aqueous solubility was greatly enhanced by the complexation with a family of cyclosophoraoses synthesized in R .meliloti. Nuclear magnetic resonance (NMR) spectroscopic analysis showed that the chemical shifts of the aromatic ring moieties of the luteolin were changed greatly by the complexation with cyclosophoraoses. Fourier transform infrared (FTIR) spectroscopic analysis also showed a restricted vibrational pattern in carbonyl stretching region of the luteolin due to the complexation. This effective complex formation of cyclosophoraoses with a plant flavone, luteolin, suggests that rhizobial cyclosophoraoses play an important role as a solubility enhancer of the hydrophobic legume-derived flavonoids.

Chiral separation of catechin by capillary electrophoresis using mono-, di-, tri-succinyl-β-cyclodextrin as chiral selectors

The chiral separation of (+/-)-catechin was investigated by capillary electrophoresis using characterized succinyl-beta-cyclodextrins (Suc-beta-CDs) with one to three degree of substitution values. The effects of nature and concentration of Suc-beta-CDs and running buffer pH on the migration time and resolution of (+/-)-catechin are discussed. All three kinds of Suc-beta-CDs show a clear baseline separation of (+/-)-catechin in capillary electrophoresis. Mono-Suc-beta-CD effectively separated (+/-)-catechin, and additional substituted CDs (di- and tri-Suc-beta-CD) were capable of chiral separation at a broad pH range. The optimum running conditions were found to be 100 mM borate buffer (pH 9.8) containing 5 mM mono-Suc-beta-CD with no methanol organic modifier.

Solubility enhancement of α-naphthoflavone by synthesized hydroxypropyl cyclic-(1→2)-β-d-glucans (cyclosophoroases)

Rhizobium leguminosarum produces unbranched cyclic β-1,2-glucans, cyclosophoraoses (Cys). In the present study, Cys were modified with hydroxypropyl groups via a one step chemical derivatization and the complexation ability and solubility enhancement of hydroxypropyl cyclosophoraoses (HP Cys) with α-naphthoflavone (α-NF) were investigated. In the presence of HP Cys, the aqueous solubility of α-NF greatly increased up to 257-fold. Complex formation of HP Cys and α-NF was confirmed by nuclear magnetic resonance (NMR), Fourier-transform infrared (FT-IR) spectroscopy, and differential scanning calorimetry (DSC). Furthermore, the morphological structure of α-NF with HP Cys was examined using scanning electron microscopy (SEM). A hypothetical model was proposed based on molecular dynamics (MD) simulations and a docking study of α-NF with HP Cys. Our results suggest that HP Cys form complexes with α-NF and can be utilized as a promising solubilizer. This is the first study to identify carbohydrates that can enhance the solubility of α-NF.

Rosmarinic acid, active component of Dansam-Eum attenuates ototoxicity of cochlear hair cells through blockage of caspase-1 activity.

Cisplatin causes auditory impairment due to the apoptosis of auditory hair cells. There is no strategy to regulate ototoxicity by cisplatin thus far. Dansam-Eum (DSE) has been used for treating the central nerve system injury including hearing loss in Korea. However, disease-related scientific investigation by DSE has not been elucidated. Here, we demonstrated that DSE and its component rosmarinic acid (RA) were shown to inhibit apoptosis of the primary organ of Corti explants as well as the auditory cells. Administration of DSE and RA reduced the thresholds of the auditory brainstem response in cisplatin-injected mice. A molecular docking simulation and a kinetic assay show that RA controls the activity of caspase-1 by interaction with the active site of caspase-1. Pretreatment of RA inhibited caspase-1 downstream signal pathway, such as the activation of caspase-3 and 9, release of cytochrome c, translocation of apoptosis-inducing factor, up-regulation of Bax, down-regulation of Bcl-2, generation of reactive oxygen species, and activation of nuclear factor-κB. Anticancer activity by cisplatin was not affected by treatment with RA in SNU668, A549, HCT116, and HeLa cells but not B16F10 cells. These findings show that blocking a critical step by RA in apoptosis may be useful strategy to prevent harmful side effects of ototoxicity in patients with having to undergo chemotherapy.

Anti-angiogenic effects of the water extract of HangAmDan (WEHAD), a Korean traditional medicine.

We investigated the anti-angiogenic effects of the water extract of HangAmDan (WEHAD), which is a crude extract of nine Korean medicinal substances of animal and plant origin. In human umbilical vein endothelial cells, WEHAD significantly inhibited bFGF-induced proliferation, adhesion, migration, and capillary tube formation. We used an antibody array to perform an analysis of signaling proteins, which showed up-regulated expression of various proteins including RAD51, RAD52, and p73, and down-regulated expression of pFAK. Blood vessel formation in a chick chorioallantoic membrane (CAM) treated with WEHAD was markedly reduced in length compared with a PBS-treated control group. These results suggest that inhibition of angiogenesis by WEHAD may be the mechanism of action for the anti-cancer effects of HAD.

Solubility and bioavailability enhancement of ciprofloxacin by induced oval-shaped mono-6-deoxy-6-aminoethylamino-β-cyclodextrin

Ciprofloxacin is a broad-spectrum fluoroquinolone antibiotic used to treat bacterial infections; however, its limited aqueous solubility inhibits its broader clinical uses. This study investigated the complexation effect of mono-6-deoxy-6-aminoethylamino-β-cyclodextrin on the aqueous solubility and bioavailability of ciprofloxacin. During complexation, the oval-shaped cavity induced by mono-aminoethylamine substitution on the primary rim of β-cyclodextrin, was considered to be a key factor according to NMR spectroscopy and molecular modeling studies. The ciprofloxacin with mono-6-deoxy-6-aminoethylamino-β-cyclodextrin complex was characterized using FE-SEM, DSC, FT-IR, T1 relaxation, 2D NOESY, and DOSY NMR spectroscopy and molecular modeling studies. The solubility property of ciprofloxacin complexed with mono-6-deoxy-6-aminoethylamino-β-cyclodextrin was enhanced by seven-fold compared to that of pure ciprofloxacin. Furthermore antibacterial activity of that complex against methicillin-resistant Staphylococcus aureus was enhanced and it clearly showed the growth inhibition. The mono-6-deoxy-6-aminoethylamino-β-cyclodextrin has the potential to be utilized for other oblong guest molecules besides ciprofloxacin based on the novel induced elliptical cavity.

Antidepressant effect of Stillen

Stillen™ has been used to treat patients with gastric mucosal ulcers and has an anti-inflammatory effect. It is well-known that neuro-inflammatory reactions are related to depression. Here we evaluated the antidepressant-like effect of Stillen™ on mice subjected to the forced swimming test (FST). Stillen™ and eupatilin (a major component of Stillen™) significantly decreased immobility times compared with the FST control group. In the Stillen™-administered group, increased levels of 5-hydroxytryptamine (serotonin) and brain-derived neurotrophic factor protein were observed in the hippocampus. Nissl bodies also increased in the hippocampus neuronal cytoplasm of the Stillen™-administered group. Stillen™ decreased levels of interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (at the mRNA and protein levels) in the hippocampus and serum, compared with the control group. In addition, the mRNA expression of estrogen receptor-β increased after Stillen™ administration in the hippocampus. These findings suggest that Stillen™ should be viewed as a candidate antidepressant.

Intermolecular complexation of low-molecular-weight succinoglycans directs solubility enhancement of pindolol

The low-molecular-weight succinoglycans isolated from Sinorhizobium meliloti are repeating octasaccharide units consisting of monomers, dimers, and trimers. Pindolol is a beta-blocker used to treat cardiovascular disorders. We investigated the formation of complexes between pindolol and low-molecular-weight succinoglycan monomers (SGs). Even though SGs have a linear structure, the solubility of pindolol in the presence of SGs was increased up to 7-fold compared with methyl-β-cyclodextrin reported as the best solubilizer of pindolol. Complexation of SGs with pindolol was confirmed by nuclear magnetic resonance, Fourier-transform infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy. Formation constants of complexes were determined from phase solubility diagrams. Conformation of complex was suggested based on a molecular docking study. The present study indicated that formation of pindolol/SGs complexes not only resulted in increased pindolol solubility but also could be useful for improving its clinical application as it did not affect cell viability.