An ultrasensitive and dual-recognition SERS biosensor based on Fe3O4@Au-Teicoplanin and aptamer functionalized Au@Ag nanoparticles for detection of Staphylococcus aureus

An ultrasensitive and dual-recognition surface-enhanced Raman scattering (SERS) biosensor for Staphylococcus aureus (S. aureus) was constructed, which was based on teicoplanin (Tcp) functionalized gold-coated magnet nanoparticles (Fe3O4@Au-Tcp NPs) as capture probe and S. aureus aptamer (Apt) functionalized silver coated gold nanoparticles (Au@Ag-DTNB-Apt NPs) as signal probe. Both Au NPs and Au@Ag NPs were prepared by a green synthesis method. Especially, the synthesis method of Au@Ag NPs reduced by chitosan (CS) was first reported in this work. Due to the great SERS enhancement based on the hot spot effect between Au NPs and Au@Ag NPs, and the dual-recognition ability based on Tcp and Apt, the SERS biosensor was ultrasensitive and specific. A detection limit of 1.09 CFU mL-1 with a broad dynamic linear (7.6 × 101-7.6 × 107 CFU mL-1) was achieved within 50 min without interference by other bacteria. Moreover, the SERS biosensor could be applied for detection of S. aureus in milk and orange juice samples. This study provides a green, rapid and ultrasensitive method to detect S. aureus, and also explores the high utilization value of CS and Tcp, which has a broad application prospect in detection of pathogenic bacteria.