A newly developed beads mill was used to create well-dispersed suspensions of TiO2 (titania) nanoparticles
in methyl methacrylate (MMA) and TiO2−PMMA nanocomposites were synthesized by subsequent
polymerization of the TiO2−MMA suspension. Beads milling successfully broke up titania nanoparticle
agglomerates with the addition of the coupling agent (3-acryloxypropyl) trimethoxysilane (APTMOS) to the
titania−MMA suspension. Agglomerated particles were broken up into primary particles as small as 10 nm
in suspensions with nanoparticle mass fractions as high as 0.05. Well-dispersed suspensions of titania
nanoparticles had reduced UV transmission but visible light transmittance similar to pure MMA. TEM images
showed that the milled nanoparticles remained well dispersed in titania−PMMA nanocomposites, and the
addition of titania nanoparticles to PMMA increased the PMMA thermal stability. Spin-coated titania−PMMA
films had higher refractive indices than pure PMMA films, with film of higher titania weight percent having
higher refractive indices.
Legionnaires’ disease, predominantly caused by the bacterium Legionella pneumophila, has increased in prevalence worldwide. The most common mode of transmission of Legionella is inhalation of contaminated aerosols, such as those generated by cooling towers. Simple, rapid and accurate methods to enumerate L. pneumophila are required to prevent the spread of this organism. Here, we applied a microfluidic device for on-chip fluorescent staining and semi-automated counting of L. pneumophila in cooling tower water. We also constructed a portable system for rapid on-site monitoring and used it to enumerate target bacterial cells rapidly flowing in the microchannel. A fluorescently-labelled polyclonal antibody was used for the selective detection of L. pneumophila serogroup 1 in the samples. The counts of L. pneumophila in cooling tower water obtained using the system and fluorescence microscopy were similar. The detection limit of the system was 104 cells/ml, but lower numbers of L. pneumophila cells (101 to 103 cells/ml) could be detected following concentration of 0.5–3 L of the water sample by filtration. Our technique is rapid to perform (1.5 h), semi-automated (on-chip staining and counting), and portable for on-site measurement, and it may therefore be effective in the initial screening of Legionella contamination in freshwater.
Quality assurance is one of the fundamental ways of preventing infections from foodborne pathogens such as Escherichia coli O157:H7, which produces a deadly toxin. Simple, rapid, and accurate methods for the detection of foodborne pathogens are necessary for healthcare management. In the present study, we applied our microfluidic device, which uses a fluorescent staining-based detection system, to enumerate E. coli O157:H7 cells in lettuce and beef samples. E. coli O157:H7 cells spiked into lettuce or beef samples were collected using a 0.2-μm-pore-sized filter or a two-step centrifugation process. The recovery ratios of inoculated E. coli O157:H7 cells from the lettuce and beef samples counted using fluorescence microscopy were 84 (± 10)% and 90 (± 7.3)%, respectively. The counts of E. coli O157:H7 inoculated into lettuce and beef obtained using the microfluidic system were close to the counts obtained using fluorescence microscopy. Our microfluidic approach offers a semiautomated platform for the quantitative detection of microbial cells from complex food samples and facilitates quantification of microbes in food and food production lines within 1 hr.
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