S. Choi

Characterization and Properties of P(VdF-HFP)-Based Fibrous Polymer Electrolyte Membrane Prepared by Electrospinning

Microporous fibrous membranes were prepared from poly(vinylidenefluoride-co-hexafluoropropylene) P(VdF-HFP) solutions in an acetone/N,N-dimethylacetamide mixture using the electrospinning method. Varying the P(VdF-HFP) polymer concentration in electrospinning can easily control the pore size and the porosity of the electrospun fibrous membranes (ES-FMs). The usefulness of the ES-FMs as a matrix of polymer electrolyte for a lithium-ion polymer battery with high performance was evaluated. Electrospun fibrous polymer electrolyte membranes (ES-FPEMs) showed excellent electrochemical properties of ionic conductivity, higher than 1 X 10 - 3 S/cm at room temperature, and the electrochemical stability window, up to 4.5 V vs. Li + /Li. At a C/2 rate, the prototype cell using the ES-FPEM showed a good charge/discharge property, with little capacity fade under constant current and constant voltage conditions at 20 and 60°C.

Comparison of the effect of different immunological adjuvants on the antibody and T-cell response to immunization with MUC1-KLH and GD3-KLH conjugate cancer vaccines

While the importance of immunological adjuvants for optimal induction of antibody and T-cell responses against tumor antigens is clear, the relevant potency of different adjuvants is not clear. We have screened 19 different immunological adjuvants with KLH conjugate vaccines containing the two human cancer antigens (MUC1 peptide and GD3 ganglioside) in the mouse. ELISA assays for IgM and IgG antibody responses as well as proliferation and cytokine release (IFN-gamma and IL-4) for T-cell responses were performed. Six adjuvants stood out as being especially effective for induction of IgM and IgG antibodies against both MUC1 and GD3: QS-21, TiterMax, MoGM-CSF, MPL/DETOX and CpG ODN. Of these QS-21, MPL/DETOX and MoGM-CSF were uniformly effective at inducing potent proliferation and potent IFN-gamma and IL-4 responses against KLH while TiterMax and CpG ODN generated potent IFN-gamma responses but less potent proliferation or IL-4 release. Overall, as in our previous experience, QS-21 was the most effective adjuvant. There was no clear evidence for induction of T-cell immunity against either GD3 or MUC1 with any of the adjuvants. There was a strong correlation between the antibodies induced against MUC1 and GD3 with different immunological adjuvants and the strength of the IFN-gamma release against KLH. This suggests that the primary role of adjuvants in the context of these conjugate vaccines may be induction of higher levels of T-cell immunity against KLH, which then leads to higher levels antibody against the conjugated antigens.

Electrochemical and Spectroscopic Properties of Electrospun PAN-Based Fibrous Polymer Electrolytes

Microporous fibrous polymer electrolytes were prepared by immersing electrospun poly(acrylonitrile) (PAN)-based fibrous membranes into lithium salt-based electrolytes. They showed high ionic conductivities of up to 1.0 X 10 - 3 S/cm at 20°C, and sufficient electrochemical stabilities of up to 4.5 V. Their ion conduction depended on the physicochemical properties of the lithium salt-based electrolytes trapped in pores, as well as on the interactions among the Li + ion, the carbonate, and the PAN. From the Fourier transform-Raman data, lithium ion transport was mainly achieved by the lithium salt-based electrolytes in pores via the interaction between the Li + ion and the C=O group of carbonate molecules, and was also affected by the PAN through the interaction between the Li + ion and the C≡N groups of PAN. Their electrochemical stabilities were enhanced by the swelling of the electrospun PAN nanofibers because of the dipolar interaction between the C≡N groups of PAN and the C=O groups of carbonate in the lithium salt-based electrolytes. Prototype cells using electrospun PAN-based fibrous polymer electrolytes thus showed different cyclic performances, according to the composition of the lithium salt-based electrolytes. The prototype cell with 1 M LiPF 6 -ethylene carbonate/dimethyl carbonate (1/1) showed the highest discharge capacity and the most stable cyclic performance among them.

A new antitumor agent: methyl sulfonium perchlorate of echinomycin.

Newly modified-echinomycin such as S-methylated sulfonium perchlorate of echinomycin (1), monosulfoxide (2), disulfoxid (3) and sulfone (4) have been prepared and evaluated for in vitro biological activities of cytotoxicity against P388, B16 and SNU-16 as well as in vivo antitumor activity against murine leukemia P388 and melanoma B16.

Characterizing X-ray detectors for prototype digital breast tomosynthesis systems

The digital breast tomosynthesis (DBT) system is a newly developed 3-D imaging technique that overcomes the tissue superposition problems of conventional mammography. Therefore, it produces fewer false positives. In DBT system, several parameters are involved in image acquisition, including geometric components. A series of projections should be acquired at low exposure. This makes the system strongly dependent on the detectors characteristic performance. This study compares two types of x-ray detectors developed by the Korea Electrotechnology Research Institute (KERI). The first prototype DBT system has a CsI (Tl) scintillator/CMOS based flat panel digital detector (2923 MAM, Dexela Ltd.), with a pixel size of 0.0748 mm. The second uses a-Se based direct conversion full field detector (AXS 2430, analogic) with a pixel size of 0.085 mm. The geometry of both systems is same, with a focal spot 665.8 mm from the detector, and a center of rotation 33 mm above the detector surface. The systems were compared with regard to modulation transfer function (MTF), normalized noise power spectrum (NNPS), detective quantum efficiency (DQE) and a new metric, the relative object detectability (ROD). The ROD quantifies the relative performance of each detector at detecting specified objects. The system response function demonstrated excellent linearity (R2>0.99). The CMOS-based detector had a high sensitivity, while the Anrad detector had a large dynamic range. The higher MTF and noise power spectrum (NPS) values were measured using an Anrad detector. The maximum DQE value of the Dexela detector was higher than that of the Anrad detector with a low exposure level, considering one projection exposure for tomosynthesis. Overall, the Dexela detector performed better than did the Anrad detector with regard to the simulated Al wires, spheres, test objects of ROD with low exposure level. In this study, we compared the newly developed prototype DBT system with two different types of x-ray detectors for commercial DBT systems. Our findings suggest that the Dexela detector can be applied to the DBT system with regard to its high imaging performance.

A feasibility study for anatomical noise reduction in dual-energy chest digital tomosynthesis

Lung cancer is the leading cause of cancer death worldwide. Thus, early diagnosis is of considerable importance. For early screening of lung cancer, computed tomography (CT) has been used as the gold standard. Chest digital tomosynthesis (CDT) is a recently introduced modality for lung cancer screening with a relatively low radiation dose compared to CT. The dual energy material decomposition method has been proposed for better detection of pulmonary nodules by means of reducing anatomical noise. In this study, the possibility of material decomposition in CDT was tested by both a simulation study and an experimental study using a CDT prototype. The Geant4 application for tomographic emission (GATE) v6 and tungsten anode spectral model using interpolating polynomials (TASMIP) codes were used for the simulation study to create simulated phantom shapes consisting of five inner cylinders filled with different densities of bone and airequivalent materials. Furthermore, the CDT prototype system and human phantom chest were used for the experimental study. CDT scan in both the simulation and experimental studies was performed with linear movement and 21 projection images were obtained over a 30 degree angular range with a 1.5 degree angular interval. To obtain materialselective images, a projectionbased energy subtraction technique was applied to high and low energy images. The resultant simulation images showed that dual-energy reconstruction could achieve an approximately 32% higher contrast to noise ratio (CNR) in images and the difference in CNR value according to bone density was significant compared to single energy CDT. Additionally, image artifacts were effectively corrected in dual energy CDT simulation studies. Likewise the experimental study with dual energy produced clear images of lung fields and bone structure by removing unnecessary anatomical structures. Dual energy tomosynthesis is a new technique; therefore, there is little guidance regarding its integration into clinical practice and this study can be used to improve the diagnostic efficiency of lung field and spinal bone screening using CDT.

In Vitro chemosensitivity test of SK-302B on human colon carcinoma cell lines

SK-302B, an antibiotic purified from soilStreptomyces sp. 302, was structurally identified as echinomycin (C50H66N11S2). In the present experiment, the possibility of SK-302B as an anticolon cancer agent was investigated by using chemosensitivity system (MTT assay, clonogenic assay). Treatment of SK-302B on various colon cancer cell lines resulted in a significant cytotoxicity and tumor colony formation inhibition. These studies showed that SK-302B had a potent inhibition on colon cancer cells.

The growth inhibitiory effect of new pyrrolo[1,2-α]benzimidazole derivatives on human gastric cancer cells

In the course of screening synthetic compounds to inhibit tumor cell growth, pyrrolo[1,2-α] benzimidazole (PBI), an intermediate of azamitosene, was found to inhibit a proliferation of gastric cancer cell lines. Despite a potential cytotoxic activity against solid tumor cells as opposed to that against rapidly-doubled leukemic cells, there has been no report on the inhibition of gastric cancer cell line by PBI and its derivatives. The present experiment was designed to determine if PBI derivatives can effectively inhibit the cellular proliferation of gastric cancer cells by usingin vitro as well asin vivo chemosensitivity system (MTT assay, clonogenic assay and human tumor xenografted assay). Of the tested PBI derivatives, PBI (18) and PBI (20), displayed the effective growth inhibition of cultured gastric cancer cells or even in the xenografted nude mouse model.

Improvement of material decomposition and image quality in dual-energy radiography by reducing image noise

Although digital radiography has been widely used for screening human anatomical structures in clinical situations, it has several limitations due to anatomical overlapping. To resolve this problem, dual-energy imaging techniques, which provide a method for decomposing overlying anatomical structures, have been suggested as alternative imaging techniques. Previous studies have reported several dual-energy techniques, each resulting in different image qualities. In this study, we compared three dual-energy techniques: simple log subtraction (SLS), simple smoothing of a high-energy image (SSH), and anti-correlated noise reduction (ACNR) with respect to material thickness quantification and image quality. To evaluate dual-energy radiography, we conducted Monte Carlo simulation and experimental phantom studies. The Geant 4 Application for Tomographic Emission (GATE) v 6.0 and tungsten anode spectral model using interpolation polynomials (TASMIP) codes were used for simulation studies and digital radiography, and human chest phantoms were used for experimental studies. The results of the simulation study showed improved image contrast-to-noise ratio (CNR) and coefficient of variation (COV) values and bone thickness estimation accuracy by applying the ACNR and SSH methods. Furthermore, the chest phantom images showed better image quality with the SSH and ACNR methods compared to the SLS method. In particular, the bone texture characteristics were well-described by applying the SSH and ACNR methods. In conclusion, the SSH and ACNR methods improved the accuracy of material quantification and image quality in dual-energy radiography compared to SLS. Our results can contribute to better diagnostic capabilities of dual-energy images and accurate material quantification in various clinical situations.

The effect of cyclosporin A on the growth of human glioma cell lines

Cyclosporin A, an potent immunosuppressant, has been known to be one of the modulators of drug resistance as well as a cytostatic drug. Despite many attempts to basic or clinical application of cyclosporin A, there are few reports on the inhibition of brain tumor cells. In the present experiment, the possibility of cyclosporin A as synergic adjuvant was investigated by MTT assay, [3H] thymidine uptake and through flowcytometric analysis. Sole treatment of cyclosporin A on the CRT and CH235-MG glioma cell line revealed dose dependent cytotoxicity within a range of tested dose. Combined treatment of cyclosporin A with ACNU, BCNU and hydroxyurea on various glioma cancer cell line led to a significant synergistic cytotoxicity as well as inhibition of DNA synthesis with dose-dependency. In addition, cyclosporin A alone or combined treatment caused discernible changes of cell cycle in the tested cells. These data provide that cyclosporin A could potentiate the effect of nitrosourea compoundsin vitro on human glioma cells.