Fluorescent Janus emulsions for biosensing ofListeria monocytogenes

Here we report a sensing method forListeria monocytogenesbased on the agglutination of all-liquid Janus emulsions. This two-dye assay enables the rapid detection of traceListeriain less than 2 h via an emissive signal produced in response toListeriabinding. The biorecognition interface between the Janus emulsions is assembled by attaching antibodies to a functional surfactant polymer with a tetrazine/transcyclooctene click reaction. The strong binding betweenListeriaand theListeriaantibody located at the hydrocarbon surface of the emulsions results in the tilting of the Janus structure from its equilibrium position to produce emission that would ordinarily be obscured by a blocking dye. This method provides rapid and inexpensiveListeriadetection with high sensitivity (<100 CFU/mL in 2 h) that can be paired with many antibody or related recognition elements to create a new class of biosensors.

Implication of exofacial thiol groups in the reducing activity ofListeria monocytogenes

Listeria monocytogenesgrowing in BHI in anaerobic condition leads a decrease of redox potential at pH7 (Eh7) from 0 to −250 mV. An investigation of mechanisms involved in this reducing activity shows the implication of thiol groups located on the bacterial cell surface. Indeed, after reduction of media to −250 mV, only thiol-reactive reagents could restore the initialEh7value. Moreover, the growth ofL. monocytogenesin anaerobic condition is characterized by a reduction then acidification phases. This suggests a sensor mechanism of environmentalEh7to convert the metabolism way from the first phase to the second. Finally, the concentration of exofacial thiol still increase strongly during the acidification phase ofL. monocytogenes, even after reach the minimal value ofEh7. These results suggest that maintaining the exofacial thiol (−SH) groups in a reduced state do not depend on an active mechanism. Thiol groups appear to be displayed by membrane proteins or cell wallbound proteins and may participate in protecting cells against oxidative stress.

A G-quadruplex DNAzyme-based LAMP biosensing platform for a novel colorimetric detection ofListeria monocytogenes

A LAMP-based method for the visual detection ofListeria monocytogeneshas been developed by employing DNAzyme-catalyzed cascade amplification of the colorimetric signal.