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 H 2 O 2 to reduce SiO 2 @MnO 2 nanocomposites into Mn 2+ , resulting in significant impedance changes in the rapid and ultrasensitive detection of Salmonella typhimurium ( S . typhimurium ). The captured S . typhimurium monoclonal antibodies (MAb 1 ) 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 (MAb 2 ) were immobilized on the surface of the SiO 2 @MnO 2 nanocomposites, which could react with the MBs- S . typhimurium conjugates to form the MBs- S . typhimurium -SiO 2 @MnO 2 sandwich complexes. The MnO 2 on the surface of the sandwich complexes was reduced into Mn 2+ by using H 2 O 2 achieving obvious impedance change that could be detected by the interdigitated microelectrodes. The recoveries for S . typhimurium cells at the concentrations between 2.0 × 10 1 and 2.0 × 10 5 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.