ABSTRACT
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.
Subject(s)
Bacillus subtilis/physiology , Microfluidic Analytical Techniques/instrumentation , Spores, Bacterial/physiology , Aniline Compounds/chemistry , Bacillus subtilis/chemistry , Bacillus subtilis/cytology , Cell Shape/physiology , Electric Conductivity , Equipment Design , Microfluidic Analytical Techniques/methods , Nanotechnology , Spores, Bacterial/chemistry , Spores, Bacterial/cytologyABSTRACT
A new type of nanobiodetector based on a limited number of polyaniline nanofibrils has been designed and tested against bacteria Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli and Enterococcus faecalis. The cells attaching conducting nanofibrils modify locally the electrical conductivity making the polymer nanowires electrically inhomogeneous. The "defects" accumulate in nanofibrils changing suddenly their electrical conductivity above a threshold density (the percolation limit), enabling an easy flow of the charge carriers. The results are unique: the device works like an "ON-OFF" switch with nearly linear response above a threshold number of cells in the suspension examined, which is of an order of 10(5) to 10(6) CFU per 1 ml. Such a behaviour is important for bio-alarm systems, environmental monitoring and medical applications.
Subject(s)
Aniline Compounds/chemistry , Bacterial Adhesion , Biosensing Techniques/methods , Nanostructures/chemistry , Biosensing Techniques/instrumentation , Electric Conductivity , Electrodes , Enterococcus faecalis/physiology , Equipment Design , Escherichia coli/physiology , Klebsiella pneumoniae/physiology , Pseudomonas aeruginosa/physiology , Sensitivity and SpecificityABSTRACT
5-Fluorouracil residues can form cyclobutane-type photodimers in a direct excitation stacking-controlled process. The stacking also has an important effect on the photohydration of uracil and 5-fluorouracil in our model compounds 5RUra(CH2)35FUra, where R = H, CH3, C2H5, C3H7, F or Cl.
