A colorimetric sandwich assay based on magnetic separation of Brevinin-1BW-functionalized magnetic beads and porcine IgG for the detection of Staphylococcus aureus.

A novel strategy integrating Brevinin-1BW (BW)-functionalized magnetic bead-based separation with a colorimetric immunoassay was developed to concentrate and enrich Staphylococcus aureus (S. aureus) from sample matrices using magnetic beads functionalized with antimicrobial peptide BW (MBs-BW) as carriers. To ensure the selectivity of the method, horseradish peroxidase (HRP)-labeled porcine IgG (HRP-porcine IgG) was used as a molecular recognition reagent and signal amplification probe. MBs-BW/S. aureus/HRP-porcine IgG probe sandwich complex was successfully obtained. HRP chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB) was used to realize the chromogenic reaction. Finally, S. aureus was quantitatively analyzed based on the color signal generated. Under the optimal conditions, the assay showed a response in the concentration range of 1.0 × 10-1.0 × 10 CFU/mL of S. aureus, and the detection limit was as low as 60 CFU/mL. This method does not require complicated sample pretreatment, and the operation process is fast and simple, which can directly complete the whole process of bacterial enrichment and detection. The recovery of this strategy in different types of spiked samples reached 86.8-97.8%, and the analytical results of this strategy were highly consistent with those of the conventional plate counting method. This strategy provides a new way for the rapid detection of S. aureus in complex samples.