An impedance biosensor based on magnetic nanobead net and MnO2 nanoflowers for rapid and sensitive detection of foodborne bacteria.

Screening of pathogenic bacteria in foods is an effective way to prevent foodborne diseases. In this study, an impedance biosensor was developed for rapid and sensitive detection of Salmonella typhimurium using multiple magnetic nanobead (MNB) nets in a ring channel for continuous-flow separation of target bacteria from 10 mL of sample, manganese dioxide nanoflowers (MnO 2 NFs) for efficient amplification of biological signal, and an interdigitated microelectrode for sensitive measurement of impedance change. First, the MNBs modified with capture antibodies were vortically injected from outer periphery of this ring channel to form multiple ring MNB nets at specific locations with high gradient magnetic fields. Then, the bacterial sample was continuous-flow injected, resulting in specific capture of target bacteria onto the nets, and the MnO 2 NFs modified with detection antibodies were injected to form MNB-bacteria-MnO 2 NF complexes. After the complexes were washed with deionized water to remove excessive nanoflowers and residual ions, H 2 O 2 with poor conductivity was injected to reduce MnO 2 NFs to conductive Mn2+ at neutral medium, leading to impedance decrease. Finally, impedance change was measured using the microelectrode for quantitative determination of Salmonella. This biosensor was able to separate ~60% of Salmonella from 10 mL of bacterial sample and detect Salmonella with a linear range of 3.0 × 101 to 3.0 × 106 CFU/mL in 1.5 h with lower detection limit of 19 CFU/mL. This biosensor might be further improved with higher sensitivity using a larger volume (100 mL or more) for routine screening of foodborne bacteria without bacterial pre-culture. • Magnetic nanobead nets were formed to separate Salmonella from large-volume sample. • MnO 2 nanoflowers were first used to amplify impedance signal for bacteria detection. • This impedance biosensor could detect Salmonella as low as 19 CFU/mL in 1.5 h. • The mean recovery of Salmonella in spiked chicken samples was 101.8%. • This biosensor might be promising for bacterial routine screening without pre-enrichment. [ABSTRACT FROM AUTHOR]