Rapid and ultrasensitive detection of Salmonella typhimurium using a novel impedance biosensor based on SiO2@MnO2 nanocomposites and interdigitated array microelectrodes

A novel impedance biosensor was developed based on the interdigitated microelectrodes using H2O2 to reduce SiO2@MnO2 nanocomposites into Mn2+, resulting in significant impedance changes in the rapid and ultrasensitive detection of Salmonella typhimurium (S. typhimurium). The captured S. typhimurium monoclonal antibodies (MAb1) were assembled on the outer layer of the magnetic beads (MBs) for specific enrichment and isolation of S. typhimurium cells in complex samples. The recognized S. typhimurium monoclonal antibodies (MAb2) were immobilized on the surface of the SiO2@MnO2 nanocomposites, which could react with the MBs- S. typhimurium conjugates to form the MBs- S. typhimurium -SiO2@MnO2 sandwich complexes. The MnO2 on the surface of the sandwich complexes was reduced into Mn2+ by using H2O2 achieving obvious impedance change that could be detected by the interdigitated microelectrodes. The recoveries for S. typhimurium cells at the concentrations between 2.0 × 101 and 2.0 × 105 CFU/mL were 83.1 %–97.0 % in the spiked milk samples. The limit of detection of this biosensor for S. typhimurium cells in the spiked milk samples was 21 CFU/mL. This approach possesses the merits of simple operation, high sensitivity, and low cost, potentially enabling this device to be a lab-on-a-chip for rapid screening of foodborne pathogens.