In situ immuno-magnetic concentration-based biosensor systems for the rapid detection of Listeria monocytogenes

A plastic module for in situ immuno-magnetic concentration (IMC) was devised by engraving acrylics and physically combining the system with a rapid test device to detect foodborne pathogen. The IMC module-installed analytical system consisted of three compartments for magnetic separation, sample medium absorption, and analysis of the target microorganism. To experimentally simulate a practical situation, immuno-magnetic beads were prepared by coupling monoclonal antibodies specific to Listeria monocytogenes, which was used as a model analyte, to chemically functionalized beads. Under the optimal conditions, the IMC module condensed the medium by a factor of 100 (e.g., from 10 mL to 100 μL) within 5 min and enriched the microorganism by about 60-fold. This concentrated sample was then analyzed using two different analytical systems based on lateral flow, i.e., ELISA-on-a-chip and immuno-chromatographic assay, which had high detection capabilities, 3.6 × 10² and 6.6 × 10³ cells mL^− 1, respectively. Thus, the IMC module-installed biosensor system was able to sequentially condense a large sample volume and detect the presence of contaminants within, for example, 30 min. Therefore, this approach could be suitable for early screening of food products that may be contaminated with microorganisms.