Browsing by Author "Chiu, Yu-Fan"

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Curcumin enhances the mitomycin C-induced cytotoxicity via downregulation of MKK1/2-ERK1/2-mediated Rad51 expression in non-small cell lung cancer cells
(2011-09-15)
Ko, Jen-Chung
;
Tsai, Min-Shao
;
Weng, Shao-Hsing
;
Kuo, Ya-Hsun
;
Chiu, Yu-Fan
Curcumin (diferuloylmethane), a major active component of turmeric (Curcuma longa), has been reported to suppress the proliferation of a wide variety of tumor cells. Rad51 is a key protein in the homologous recombination (HR) pathway of DNA double-strand break repair, and HR represents a novel target for cancer therapy. A high expression of Rad51 has been reported in chemo- or radio-resistant carcinomas. Therefore, in the current study, we will examine whether curcumin could enhance the effects of mitomycin C (MMC), a DNA interstrand cross-linking agent, to induce cytotoxicity by decreasing Rad51 expression. Exposure of two human non-small lung cancer (NSCLC) cell lines (A549 and H1975) to curcumin could suppress MMC-induced MKK1/2-ERK1/2 signal activation and Rad51 protein expression. Enhancement of ERK1/2 activation by constitutively active MKK1/2 (MKK1/2-CA) increased Rad51 protein levels in curcumin and MMC co-treated human lung cells. Moreover, the synergistic cytotoxic effect induced by curcumin combined with MMC was decreased by MKK1-CA-mediated enhancement of ERK1/2 activation by a significant degree. In contrast, MKK1/2 inhibitor, U0126 was shown to augment the cytotoxicity of curcumin and MMC through downregulation of ERK1/2 activation and Rad51 expression. Depletion of endogenous Rad51 expression by siRad51 RNA transfection significantly enhanced MMC and/or curcumin induced cell death and cell growth inhibition. In contrast, an overexpression of Rad51 protected lung cancer cells from synergistic cytotoxic effects induced by curcumin and MMC. We concluded that Rad51 inhibition may be an additional action mechanism for enhancing the chemosensitization of MMC by curcumin in NSCLC. (C) 2011 Elsevier Inc. All rights reserved.
Fabrication of Ni nanowires for hydrogen evolution reaction in a neutral electrolyte
(2009-08-01)
Chen, Po-Chun
;
Chang, Yun-Min
;
Wu, Pu-Wei
;
Chiu, Yu-Fan
;
材料科學與工程學系
Hydrogen evolution reaction in 1 M Na(2)SO(4) was investigated using Ni nanowires in diameter of 250 nm with exposed lengths of 20, 35, and 45 mu m, respectively. The Ni nanowires were fabricated by a direct-current pulse electrodeposition technique using an anodic aluminum oxide template, followed by selective removal of the supporting pore walls. Scanning Electron Microscope images revealed structural stabilities and X-ray diffraction pattern indicated a polycrystalline fcc phase. In current-potential (i-V) polarizations, the Ni nanowires with longer exposed lengths demonstrated larger current responses. Analysis from impedance spectroscopy confirmed increasing double-layer capacitances with longer Ni nanowires. in galvanostatic lifetime experiments, the freestanding Ni nanowires exhibited a reduced overpotential over that of supported ones. Similar procedures were performed for the oxygen evolution reaction in both i-V and lifetime measurements. For the Ni nanowires of 45 pm length, we estimated the energy cost for hydrogen production was 5.24 x 10(5) J/mole. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.
Galvanostatic Pulse Plating of PtRu Nanoparticles for Direct Methanol Fuel Cells
(2008)
Hsieh, Yu-Chi
;
Lu, Yung-Jean
;
Wu, Pu-Wei
;
Chang, Yun-Min
;
Chiu, Yu-Fan
A galvanostatic pulse electrodeposition technique of preparing nanoparticulate PtRu electrocatalyst for direct methanol fuel cells has been demonstrated. After extensive cyclic voltammetric analysis, we determined the optimized parameters for the methanol oxidation to be current on-time on 50 ms, current off-time of 400 ms, current density of 50 mA/cM, and total charge of 9.0 C/cm(2) In addition, the catalyst loading was measured at 68 mu g/cm(2) resulting in a mass activity of 213 mA/Pt. mg. The composition for the nanoparticles was confirmed as Pt(65)RU(35). High-magnification images on the specimen indicated fine particles in 4-20 nm with uniform distributions.
Modulation of Rad51, ERCC1, and thymidine phosphorylase by emodin result in synergistic cytotoxic effect in combination with capecitabine
(2011-03-01)
Ko, Jen-Chung
;
Tsai, Min-Shao
;
Kuo, Ya-Hsun
;
Chiu, Yu-Fan
;
Weng, Shao-Hsing
Thymidine phosphorylase (TP) is the rate-limiting enzyme for the activation of capecitabine (pro-drug of fluorouracil), and as a useful predictor of tumor response to capecitabine-based chemotherapy. Overexpression of Rad51 and ERCC1 induce resistance to chemotherapeutic agents. Emodin, one of the main bioactive anthraquinone derivatives in the roots and rhizomes of numerous plants, possesses potent antitumor effects. Accordingly, we aimed to explore the molecular mechanism of emodin enhances the capecitabine-induced cytotoxicity through controlling Rad51, ERCC1, and TP expression in human non-small cell lung cancer (NSCLC). The results show that capecitabine increases the phosphorylation of MKK1/2-ERK1/2 and protein levels of Rad51 and ERCC1 through enhancing the protein stability. Depletion of endogenous Rad51 or ERCC1 expression by specific small interfering RNA transfection significantly increases capecitabine-induced cell death and growth inhibition. Emodin enhances the capecitabine-induced cytotoxic effects through ERK1/2 inactivation and decreasing the Rad51 and ERCC1 protein levels induced by capecitabine. Enhancement of ERK1/2 signaling by constitutively active MKK1/2 (MKK1/2-CA) results in increasing Rad51 and ERCC1 protein levels and cell viability in NSCLC cell lines treated with emodin and capecitabine. Interestingly, emodin enhances TP mRNA and protein expression in capecitabine treated NSCLC cell lines, and depletion of the TP expression decreases the cytotoxic effects induced by capecitabine and emodin. We conclude that enhancing the cytotoxicity to capecitabine by emodin is mediated by down-regulation the expression of Rad51 and ERCC1 and up-regulation TP expression. (C) 2010 Elsevier Inc. All rights reserved.
Negative-Capacitance FinFET Inverter, Ring Oscillator, SRAM Cell, and Ft
(2018-01-01)
Li, Kai-Shin
;
Wei, Yun-Jie
;
Chen, Yi-Ju
;
Chiu, Wen-Cheng
;
Chen, Hsiu-Chih
In this work, we use thermal-ALD to prepare ferroelectric HfZrO2 (HZO) thin film with thickness from 3 to 7 nm for the NC-FinFET's gate stack. The subthreshold swing (SS) was as low as 5 mV/dec (SSmin) over 4 orders of I-D. Lower thermal budget process, CO2 far-infrared laser activation and 400 degrees C Ni silicide are employed in the 2-level metal backend integration for maintaining the orthorhombic phase in HZO thin film and minimizing the hysteresis in IV. NC-FinFET inverter has 77% higher voltage gain compared to FinFET-inverter employing HfO2 gate dielectric. NC-FinFET ring oscillator exhibit small speed and power advantages over FinFET oscillator. For the first time, NC-FET cut-off frequency (F-t) frequency is measured, 23.1 GHz or 23% higher than the control FET Ft. NC-FinFET SRAM was observed to exhibit large noise margin.
Physical Characterizations of Ni-Plated Carbon Fibers after Controlled Thermal Treatments
(2009-03-01)
Lai, Chun-Han
;
Liu, Guan-Ting
;
Wu, Pu-Wei
;
Chiu, Yu-Fan
;
Chou, Chao-Ling
Surface modifications of carbon fibers (CFs) were conducted by electroless Ni depositions. After annealing in air at 300 degrees C, we fabricated a composite in NiO/Ni/CFs configuration. The samples revealed reasonable surface uniformities without defects at the interfaces. Values for the electrical resistivity indicated a steady increase with annealing time, reaching a plateau after 72h. Results on the tensile stress exhibited a marked reduction once the NiO was formed. A thermal treatment at 700 degrees C for 48 h in air allowed complete removal of the CFs, forming NiO hollow tubes with an inner diameter of 6.50 mu m. Subsequently, they were transformed into Ni hollow tubes with a reduced inner diameter of 5.53 mu m under a hydrogen treatment at 400 degrees C for 3 h. The NiO and Ni tubes demonstrated impressive structural integrities with considerable mechanical strengths. (C) 2009 The Japan Society of Applied Physics
Templated fabrication of nanostructured Ni brush for hydrogen evolution reaction
(2010-10-01)
Lin, Sheng-Chieh
;
Chiu, Yu-Fan
;
Wu, Pu-Wei
;
Hsieh, Yi-Fan
;
Wu, Cheng-Yeou
We fabricated a nanostructured brush by carrying out Ni deposition on a through-channel anodic aluminum oxide (AAO) template, followed by removal of the AAO skeleton. The AAO was prepared by a two-step anodization process resulting in pore diameter and thickness of 350 nm and 40 mu m, respectively. Subsequently, the AAO underwent an electroless deposition involving sensitization, activation, and Ni plating, in conjunction with polyethylene glycol used as the inhibitor to prevent premature closing of pore opening. After deliberate control in relevant parameters, we obtained a conformal Ni overcoat along every pore channel leading to a reduced average pore diameter of 78 nm. Afterward, the sample was immersed in a KOH solution to remove the AAO structure, forming freestanding Ni tubules in a brush configuration. The nanostructured brush revealed considerable enhancement for hydrogen evolution reaction in both current-potential polarization and galvanostatic measurements, which were attributed to the increment in apparent surface area.
Templated fabrication of nanostructured Ni brush for hydrogen evolution reaction
(2010-10-01)
Lin, Sheng-Chieh
;
Chiu, Yu-Fan
;
Wu, Pu-Wei
;
Hsieh, Yi-Fan
;
Wu, Cheng-Yeou
We fabricated a nanostructured brush by carrying out Ni deposition on a through-channel anodic aluminum oxide (AAO) template, followed by removal of the AAO skeleton. The AAO was prepared by a two-step anodization process resulting in pore diameter and thickness of 350 nm and 40 mu m, respectively. Subsequently, the AAO underwent an electroless deposition involving sensitization, activation, and Ni plating, in conjunction with polyethylene glycol used as the inhibitor to prevent premature closing of pore opening. After deliberate control in relevant parameters, we obtained a conformal Ni overcoat along every pore channel leading to a reduced average pore diameter of 78 nm. Afterward, the sample was immersed in a KOH solution to remove the AAO structure, forming freestanding Ni tubules in a brush configuration. The nanostructured brush revealed considerable enhancement for hydrogen evolution reaction in both current-potential polarization and galvanostatic measurements, which were attributed to the increment in apparent surface area.