Showing papers by "Hsu Chih-Wei published in 2009"

Roasted coffees high in lipophilic antioxidants and chlorogenic acid lactones are more neuroprotective than green coffees.

Abstract: Oxidative stress is involved in many neurodegenerative processes leading to age-related cognitive decline. Coffee, a widely consumed beverage, is rich in many bioactive components, including polyphenols with antioxidant potential. In this study, regular and decaffeinated samples of both roasted and green coffee all showed high hydrophilic antioxidant activity in vitro, whereas lipophilic antioxidant activities were on average 30-fold higher in roasted than in green coffee samples. In primary neuronal cell culture, pretreatment with green and roasted coffees (regular and decaffeinated) protected against subsequent H2O2-induced oxidative stress and improved neuronal cell survival (green coffees increased neuron survival by 78%, compared to 203% by roasted coffees). All coffee extracts inhibited ERK1/2 activation, indicating a potential attenuating effect in stress-induced neuronal cell death. Interestingly, only roasted coffee extracts inhibited JNK activation, evidencing a distinctive neuroprotective benef...

Label-free dual sensing of DNA molecules using GaN nanowires.

Abstract: We demonstrate a rationale for using GaN nanowires (GaNNWs) in label-free DNA-sensing using dual routes of electrochemical impedance spectroscopy (EIS) and photoluminescence (PL) measurements, employing a popular target DNA with anthrax lethal factor (LF) sequence. The in situ EIS reveals that both high surface area and surface band-bending in the nanowires, providing more binding sites and surface-enhanced charge transfer, respectively, are responsible for the enhanced sensitivity to surface-immobilized DNA molecules. The net electron-transfer resistance can be readily deconvoluted into two components because of the coexistence of two interfaces, GaN/DNA and DNA/electrolyte interfaces, in series. Interestingly, the former, decreasing with LF concentration (CLF), serves as a signature for the extent of hybridization, while the latter as a fingerprint for DNA modification. For PL-sensing, the band-edge emission of GaNNWs serves as a parameter for DNA modification, which quenches exponentially with CLF as t...

Functionalized GaN nanowire-based electrode for direct label-free voltammetric detection of DNA hybridization

Abstract: This study demonstrates the utility of functionalized GaN nanowires (GaNNWs) for electrochemical detection of nucleic acids, in aqueous solution, using cyclic voltammetry. In order to link probe DNA to the NW surface, we employed an organosulfur compound, 3-mercaptopropyl trimethoxysilane (MPTS), to functionalize the GaNNW surface. Interestingly, the MPTS-modified GaNNWs exhibited a potential window of 4.5 V, the widest reported to date, with very low background current, which provides an advantage for sensing DNA immobilization/hybridization, down to sub-pM concentration, via monitoring adenine and guanine oxidation. The oxidation of guanine was characterized by its peak potential and peak current, where the former serves as a fingerprint for DNA hybridization and the latter as a parameter for the extent of hybridization. Moreover, the GaNNW-based sensor exhibited excellent consistency in hybridization-dehybridization-rehybridization cycles.