New “ON-OFF”-type nanobiodetector

A microfluidic device for real-time monitoring of Bacillus subtilis bacterial spores during germination based on non-specific physicochemical interactions on the nanoscale level

A microfluidic device for studies on the germination of bacterial spores (e.g. Bacillus subtilis) based on non-specific interactions on the nanoscale is presented. A decrease in the population of spores during germination followed by the appearance of transition forms and an increase in the number of vegetative cells can be registered directly and simultaneously by using the microfluidic device, which is equipped with a conductive polymer layer (polyaniline) in the form of a nano-network. The lab-on-a-chip-type device, operating in a continuous flow regime, allows monitoring of germination of bacterial spores and analysis of the process in detail. The procedure is fast and accurate enough for quantitative real-time monitoring of the main steps of germination, including final transformation of the spores into vegetative cells. All of this is done without the use of biomarkers or any bio-specific materials, such as enzymes, antibodies and aptamers, and is simply based on an analysis of physicochemical interactions on the nanoscale level.

In Situ Infrared Spectroscopy of Oligoaniline Intermediates Created under Alkaline Conditions

The progress of the oxidation of aniline with ammonium peroxydisulfate in an alkaline aqueous medium has been monitored in situ by attenuated total reflection (ATR) Fourier transform infrared spectroscopy. The growth of the microspheres and of the film at the ATR crystal surface, as well as the changes proceeding in the surrounding aqueous medium, are reflected in the spectra. The evolution of the spectra and the changes in the molecular structure occurring during aniline oxidation in alkaline medium are discussed with the help of differential spectra. Several processes connected with the various stages of aniline oxidation were distinguished. The progress of hydrolysis of the aniline in water and further an oxidation of aminophenol to benzoquinone imines in the presence of peroxydisulfate in alkaline medium have been detected in the spectra in real time. The precipitated solid oxidation product was analyzed by mass spectrometry. It is composed of oligomers, mainly trimers to octamers, of various molecular structures incorporating in addition to aniline constitutional units also p-benzoquinone or p-benzoquinoneimine moieties.

Intrinsically conducting polymer nanowires for biosensing

The fabrication of conductive polymer nanowires and their sensing of nucleic acids, proteins and pathogens is reviewed in this feature article.

Modeling methods for identifying critical source areas of bacteria: recent developments and future perspectives

Identification of critical source areas of bacteria in a watershed is essential to environmental management and restoration. As a result of the nonpoint and distributed nature of bacterial pollution in watersheds, it is often difficult to identify specific source areas of bacteria for remediation because bacteria collected from different sampling sites might display similar fingerprints. Over the past decade, extensive efforts have been made to identify microbial pollution sources, especially in watersheds. The primary objective of this study was to identify effective methods that can be applied to tracking critical source areas of bacteria in a watershed by a review of recent developments in several modeling methods. Comparisons of the models and their applications revealed that comprehensive watershed-scale source area tracking primarily involves two steps-geographical tracking and mathematical tracking. In terms of geographical tracking, bacterial source locations must be identified to prepare structural best management practices or low impact development for site treatments. For mathematical tracking, the quantity (strength) or release history of bacterial sources must be computed to develop total maximum daily loads (TMDLs) for bacterial load reduction and water quality restoration. Mathematically, source tracking is essentially an inverse modeling issue under uncertainty, requiring inverse modeling combined with a geostatistical method or an optimization algorithm. Consequently, combining biological methods, mathematical models, and sensor technologies (including remote sensing and in-situ sensing) provides an effective approach to identifying critical source locations of bacteria at the watershed-scale.