Publications by authors named "Nai-Tzu Chen"

34 Publications

Airborne fungi and bacteria in child daycare centers and the effectiveness of weak acid hypochlorous water on controlling microbes.

J Environ Monit 2012 Oct 21;14(10):2692-7. Epub 2012 Aug 21.

Department of Environmental and Occupational Health, College of Medicine, National Cheng Kung University, 138 Sheng-Li Road, Tainan 70403, Taiwan.

A three-week-long biological sampling scheme was conducted in two child daycare centers (CDCCs) in order to investigate interdiurnal and diurnal variations in indoor airborne microbes as well as the efficiency of weak acid hypochlorous water (WAHW) on disinfecting indoor microbes. During the second week of sampling, WAHW was sprayed using a fogger in the classroom after children had left and before they returned the next morning. An identical cycle of experiments was performed twice in the winter and spring. Without WAHW intervention, the respective mean of the indoor concentrations and I/O ratios were 8732-47581 CFU m(-3) and 0.96-2.53 for fungi, and 6706-28998 CFU m(-3) and 1.10-11.92 for bacteria, showing severe bio-contamination in the CDCCs. Moreover, a relatively high level of bacterial pollution was found at noon, whereas a greater fungal pollution could be detected in the morning and at noon. Among five school days, the fungal and bacterial pollution may be higher on Monday and on Wednesday, Thursday, and Friday, respectively. Furthermore, with WAHW intervention, the indoor microbial concentrations and I/O ratios were decreased significantly. The reduction of I/O ratios caused by WAHW disinfection was accomplished in the morning for bacteria and in the morning, at noon, and in the afternoon for fungi. In conclusion, this study clearly clarified the risky period during which children may be exposed to hazardous environments, and demonstrated the effectiveness of spraying WAHW the night before on decontaminating indoor airborne microbes on the following day, especially in the case of fungi.
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http://dx.doi.org/10.1039/c2em30113jDOI Listing
October 2012

Quantification of Legionella pneumophila by real-time quantitative PCR from samples with humic acid and ferric ion.

Sci Total Environ 2012 Jan 21;414:608-13. Epub 2011 Nov 21.

Institute of Environmental Health, College of Public Health, National Taiwan University, Taipei City 100, Taiwan.

This study determined and overcame the influences of humic acid (HA) and/or ferric ion (Fe) on quantification of Legionella pneumophila by real-time quantitative PCR (qPCR). Four commonly used DNA isolation methods, QiAamp DNA Mini Kit (Q), Q with Sepharose 4B gel column (Q/G), freeze-thaw/phenol-chloroform lysis (FT-PC), and FT-PC/G, were adopted to isolate L. pneumophila DNA from samples containing Fe alone (0-30 mg l(-1)) or Fe/HA (0/0-3/100 mg l(-1)). Among the four DNA isolation methods, Q removed HA effectively and obtained the greatest DNA yield regardless of Fe and HA concentration (P<0.05). For samples containing Fe (0.3-3 mg l(-1)) or Fe/HA (0.3/10-3/100 mg l(-1)), qPCR inhibition was found in all isolated DNA, especially in those obtained by Q/G and FT-PC/G. DNA dilution at either 10 or 100 folds reduced qPCR inhibition and increased cell recovery (P<0.05). Under 10-fold dilution, Q acquired the highest concentrations of L. pneumophila determined by qPCR. Consequently, Q with post 10-fold dilution is suggested prior to qPCR for quantifying L. pneumophila from water containing Fe (≤ 3 mg l(-1)) or Fe/HA (≤ 3/100 mg l(-1)).
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http://dx.doi.org/10.1016/j.scitotenv.2011.10.005DOI Listing
January 2012

The protease-mediated nucleus shuttles of subnanometer gold quantum dots for real-time monitoring of apoptotic cell death.

J Am Chem Soc 2010 Jun;132(24):8309-15

Center for Nanomedicine Research, National Health Research Institutes, 35 Keyan Road Zhunan, Miaoli, Taiwan.

Subnanometer photoluminescent gold quantum dots (GQDs) are functionalized with a peptide moiety that contains both nuclear export signal (NES) and nuclear localization signal (NLS) sequences. By taking advantage of its small size and great photostability, the functionalized GQDs are used to mimic the actions of nucleus shuttle proteins, especially of those activated during cell apoptotic death, to work as protease-mediated cytoplasm-nucleus shuttles for dynamic monitoring of apoptosis. The resulting construct demonstrates activation of the nuclear pore complex (NPC) of cells, for bidirectional transport between nucleus and cytoplasm. A caspase-3 recognition sequence (DEVD), placed within the NLS/NES peptide, serves as a proteolytic site for activated caspase-3. Upon the induction of apoptosis, the activated caspase-3 cleaves the functional peptide on GQDs resulting in changes of subcellular distribution of GQDs. Such changes can be quantified as a function of time, by the ratios of GQDs photoluminescence in nucleus to that in cytoplasm. As such, the NES-linker-DEVD-linker-NLS peptide enables the GQDs to function as molecular probes for the real-time monitoring of cellular apoptosis.
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http://dx.doi.org/10.1021/ja100561kDOI Listing
June 2010

Ligand exchanged photoluminescent gold quantum dots functionalized with leading peptides for nuclear targeting and intracellular imaging.

Chem Commun (Camb) 2008 Oct 8(39):4762-4. Epub 2008 Aug 8.

Center for Nanomedicine Research, National Health Research Institutes, 35 Keyand Rd. Zhunan, Mialoli 350, Taiwan.

Ligand exchanged gold quantum dots (GQDs) conjugated with cell-penetrating peptides are a new class of photoluminescent probes for nuclear targeting and intracellular imaging.
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http://dx.doi.org/10.1039/b808207cDOI Listing
October 2008