Colorimetric Detection of Urease-Producing Microbes Using an Ammonia-Responsive Flexible Film Sensor.

Urease-producing (ureolytic) microbes have given rise to environmental and public health concerns because they are thought to contribute to emissions of ammonia and to be a virulence factor for infections. Therefore, it is highly important to have the ability to detect such microbes. In this study, a poly(dimethylsiloxane) (PDMS)-based colorimetric film sensor was employed for the detection of urease-producing microbes. The sensor was able to detect the enzyme activity of commercially available urease, as the color and absorbance spectrum of the sensor was observed to change upon being exposed to the reaction catalyzed by urease. The ratio of the absorbance of the sensor at 640 nm to that at 460 nm (A640/A460) was linearly proportional to the amount of urease present. The performance of the sensor was validated by the results of a sensitivity and selectivity analysis towards thirteen different bacterial strains. Based on the development of blue color of the sensor, the tested bacteria were classified as strongly positive, moderately positive, weakly positive, or negative urease producers. The response of the sensor to ureolytic bacteria was verified using the urease inhibitor phenyl phosphorodiamidate (PPDA). Additionally, the sensor achieved the selective detection of ureolytic bacteria even in the presence of non-ureolytic bacteria. In addition, a used sensor could be reverted to its original state by being subjected to simple aeration, and in this way the same sensor could be used at least five times for the detection of bacterial urease activity.

Simple screening of microplastics in bottled waters and environmental freshwaters using a novel fluorophore.

Screening of polymeric microplastic debris can help to assess the extent to which plastics contaminate the environment. We here developed an easy- and rapid-to-perform method for the screening of plastic polymers, based on a newly employed fluorophore, namely 1-pyrenebutyric acid N-hydroxysuccinimidyl ester (PBN). The PBN fluorophore was capable of staining diverse synthetic microplastic polymers within 5 min, including those displaying various particle sizes and shapes. The fluorescence intensities of the microplastics were considerably enhanced after the short-duration staining. The screening method was shown to be highly effective in the detection of polyethylene (PE), poly(ethylene terephthalate) (PET), polyvinyl chloride (PVC), polyamide-6 (PA-6), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polyvinylidenechloride (PVDC), and polyurethane (PU), with a lowest analyzed particle size of 15 µm. Using our screening method, plastic contamination was investigated in commercially available bottled waters and environmental waters, specifically urban freshwaters. This study demonstrated high affinity levels of the newly proposed PBN fluorophore for a broad range of polymers and its ability to be used to discernibly identify polymer particles.