Sensitive Detection of Staphylococcus aureus by a Colorimetric Biosensor Based on Magnetic Separation and Rolling Circle Amplification

Staphylococcus aureus(S. aureus) is a common foodborne pathogen that causes fever, vomiting, and other intestinal symptoms, and seriously affects human health and social safety. As a result, a reliable and sensitive detection technique forS. aureusmust be developed. In this work, we proposed a sandwich assay on vancomycin functionalized magnetic beads (Van-MNPs) forS. aureusdetection based on the specific binding between IgG and targets. The Van-MNPs were used as a tool for the separation of target bacteria. The biotin-modified IgG mediates binding between DNA nanoflowers (DNFs) and the target bacteria via interacting with streptavidin. The DNFs prepared by rolling circle amplification (RCA) were employed as a nano-container to enhance the capacity of biotins, and the streptavidin-horseradish peroxidase (SA-HRP) was loaded onto DNFs to catalyze the color change of TMB. Therefore, a colorimetric biosensor based on magnetic separation and rolling circle amplification was developed. The proposed methods forS. aureusdetection showed a limit of detection (LOD) of 3.3 × 103CFU/mL and excellent specificity. The biosensor has a certain reference value for the detection ofS. aureusin juice.Keywords:Staphylococcus aureus;DNA nanoflowers;vancomycin;magnetic separation;juice