Bioconjugated magnetic nanoparticles for the detection of bacteria.

Blood culture is traditionally a time-consuming method and has not changed significantly in several decades. Using nanotechnology, such as the use of magnetic nanoparticles (MNPs), the blood culture process may be streamlined. An important advantage of using MNPs to capture bacteria is the simple separation of bacteria from biological samples using magnets. Indeed, high bacteria capture efficiencies have been realized using MNPs. The binding events between MNPs and bacteria can be tightly controlled through carefully selected biorecognition events, using molecules such as vancomycin, daptomycin, antibodies, and others. These biomolecules can be readily conjugated onto MNPs followed by tethering to bacteria, thus enabling detection using the beacon produced by the bacteria conjugated MNPs. Methods to prepare bioconjugated MNPs and their performance with bacteria are reviewed. Finally, future directions on bacteria detection using giant magnetoresistance (GMR) biosensors are discussed.

Single step, rapid identification of pathogenic microorganisms in a culture bottle.

Efforts to treat bloodstream infections, which have a relatively high mortality rate, are delayed by the lengthy multi-step process required to identify the causative bacteria. Due to this delay, broad spectrum antibiotics are prescribed on a presumptive basis, leading to the rise of antibiotic resistant microorganisms. Here, as proof of principle, we describe a colourimetric sensor that rapidly identifies opportunistic pathogenic bacteria in a single step in TSB media. The device is composed of a reaction chamber and an array of chemoresponsive dyes deposited on a substrate in a prearranged pattern. This single step, disposable, automated system can detect and identify of eight strains of bacteria, starting with clinically relevant concentrations bacteria in twenty four hours in TSB media. Thus, this technology may be used to streamline the current blood culture process by combining detection and identification in a single step.

Layer by layer assembly of biotinylated protein networks for signal amplification.

Described herein is a unique and inexpensive method that outperforms commercial methods that amplify the streptavidin-biotin recognition event. Amplification induced by streptavidin and biotinylated protein causes the formation of a large detectable polymer. This approach enjoys a 100-fold decrease in detection limit in comparison with the commercial methods.

Strong enantioselective self-recognition of a small chiral molecule.

In the present report, we have crystallized a single enantiomer and the racemate of N-3,5-dinitrobenzoyl (DNB) leucine. In both cases, the X-ray structures show clear evidence of homochiral dimerization in the solid state. Moreover, only homochiral dimers were observed in the unit cell of the racemate, a result of solid-state enantioselective complexation. The crystal structures support a chiral recognition mechanism involving two hydrogen bonds and an offset pi-pi interaction between the DNB rings.