Gold interdigitated micro-immunosensor based on Mn-MOF-74 for the detection of Listeria monocytogens

Accurate and rapid detection of foodborne pathogens is a key to prevent foodborne disease outbreaks. In this study, a novel impedance immunosensor based on a metal-organic framework (Mn-MOF-74) is used to rapidly and sensitively detect Listeria monocytogenes ( L. m ) in milk. Divalent manganese ions are released by the MOF reduction reaction mediated by hydrogen peroxide. Consequently, the impedance signal was detected by high conductive single-crystalline gold interdigitated microelectrode to achieve quantification of L. m . First, the capture antibodies (Ab 1 ) are modified on the surface of the magnetic beads to generate immunomagnetic beads (MBs@Ab 1 ), which are used specifically to separate L. m cells in the matrices. Later, the immunosensor (Mn-MOF-74@Ab 2 ) is added to the matrices to form a sandwich complex (MBs@Ab 1 - L. m -Mn-MOF-74@Ab 2 ). Henceforward, Mn 2+ is released from the sandwich composite via the action triggered by H 2 O 2 . The release of Mn 2+ significantly changes the impedance of interdigitated microelectrodes, leading to ultrasensitive detection of L. m . The recoveries for L. m cells at the concentration between 1.0 × 10 0 and 1.0 × 10 4  CFU/mL are 90.2%–101.7% in water and 88.5%–96.2% in milk. The detection limit of this approach for L. m cells in water and milk are 7.1 and 9.2 CFU/mL, respectively. This approach can achieve rapid quantification of L. m cells within 60 min, and can also be employed to monitor other foodborne pathogens.