Immunomagnetic nanobeads based on a streptavidin-biotin system for the highly efficient and specific separation of Listeria monocytogenes

Immunomagnetic separation was used to decrease the assay time for Listeria monocytogenes (LM) isolation. The coupling conditions and immunomagnetic bead (IMB) capture process were optimized. Results showed that the incubation time and separation time for 0.1 mg of 180 nm immunomagnetic nanobeads (IMB-S-180) coupled with monoclonal antibody using a streptavidin-biotin system was 45 and 3 min, respectively. Magnetic separation was affected by the separation medium and magnetic density of the magnetic separator. Capture efficiency (CE) was 94.12% when the magnetic density was 1.5 T, using 1 ml of PBS as separation medium. The IMBs exhibited highly specific binding with LM strains (CE > 90%) but low binding with non-target bacteria (CE < 5%). The CE of IMBs (0.1 mg/ml) against LM in ground beef and milk samples were 25.1% and 91.2%, respectively. These results can serve as a guide for the appropriate selection of IMBs for developing isolation processes for pathogens.