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An electrochemical immunosensor based on ferrocene (Fc)-functionalized nanocomposites was fabricated as an efficient electroactive signal probe to amplify electrochemical signals for Salmonella typhimurium detection. The electrochemical signal amplification probe was constructed by encapsulating ferrocene into S. typhimurium–specific antimicrobial peptides Magainin I (MI)-Cu3(PO4)2 organic-inorganic nanocomposites (Fc@MI) through a one-step process. Magnetic beads (MBs) coupled with antibody were used as capture ingredient for target magnetic separation, and Fc@MI nanoparticles were used as signal labels in the immunoassays. The sandwich of MBs-target-Fc@MI assay was performed using a screen-printed carbon electrode as transducer surface. The immunosensor platform presents a low limit of detection (LOD) of 3 CFU·mL−1 and a linear range from 10 to 107 CFU·mL−1, with good specificity and precision, and was successfully applied for S. typhimurium detection in milk. [ABSTRACT FROM AUTHOR]

Muir et al. [T. G. Muir, C. W. Horton, Sr., and L. A. Thompson, J. Sound Vib. 64, 539-551 (1979)] observed that the propagation direction of the sound wave in the sediment insonified by a parametric array departed significantly from the prediction of Snell's law. The wave fronts penetrated more steeply into the sediment and the attenuation at postcritical incidence was less than that predicted by the plane wave theory. It was found that mainly due to the variation of the length of the parametric array, the direction of the refracted sound wave occurs at or near the line-of-sight between the projector and the hydrophone. It has been proved, both theoretically and experimentally, that Snell's law is still valid when the length of parametric array is kept constant. At postcritical incidence, the penetration of a parametric array can be deeper due to the contribution of the lateral wave and secondary sources close to the boundary. [ABSTRACT FROM AUTHOR]

An innovative approach is presented for portable and sensitive detection of pathogenic bacteria. A novel synthetic hybrid nanocomposite encapsulating platinum nanoparticles, as a highly efficient catalyst, catalyzes the hydrolysis of the ammonia–borane complex to generate hydrogen gas. The nanocomposites are used as a label for immunoassays. A portable hand-held hydrogen detector combined with nanocomposite-induced signal conversion was applied for point-of-care testing of pathogenic bacteria. A hand-held hydrogen detector was used as the transducer. Escherichia coli O157:H7 (E. coli O157: H7), as detection target, formed a sandwich structure with magnetic beads and hybrid nanocomposites. Magnetic beads were used for separation of the sandwich structure, and hybrid nanocomposites as catalysts to catalyze the generation of hydrogen from ammonia−borane. The generated hydrogen was detected by a hydrogen detector using an electrochemical method. E. coli O157:H7 has a detection limit of 10 CFU·mL−1. The immunosensor made the hand-held hydrogen detector a point-of-care meter to be used outdoors for the detection and quantification of targets beyond hydrogen. [ABSTRACT FROM AUTHOR]

Disposable syringes were used in a novel point-of-care visual test for detecting pathogenic bacteria (Escherichia coli O157:H7 and Salmonella typhimurium). Hybrid nanoflowers composed of platinum nanoparticles and concanavalin A (Pt-nanoflowers) were prepared through a one-pot reaction and were found to be viable catalase mimics. They catalyze the decomposition of hydrogen peroxide (H2O2) to generate O2. When used as labels in immunoassays, they integrate both the functions of biological recognition and signal amplification. The disposable syringe pressure readout was combined with Pt-nanoflower signal conversion and successfully applied to a visual bacteria detection scheme. Both Escherichia coli O157:H7 and Salmonella typhimurium can be quantified with detection limits of as low as 15 and 7 CFU·mL−1, respectively.One-pot synthetic platinum nanoparticle (PtNP)-concanavalin A hybrid nanoflowers (Pt-nanoflowers), have been used as ideal signal labels for immunoassays and integrating both essential functions of biological recognition and signal amplification. Disposable syringes were used as a readout to detect pathogenic bacteria. [ABSTRACT FROM AUTHOR]