A SERS/colorimetric biosensor based on AuNSs@Ag core-shell Prussian blue nanozyme for non-interference and rapid detection of Staphylococcus aureus in milk

A AuNSs@PB@Ag-Apt surface-enhanced Raman scattering (SERS) probe has been developed by embedding Prussian blue (PB) between Au core and Ag shell. The PB SERS probe illustrates strong SERS activity in the Raman silent region of 2070 cm(-1), and has a zero background signal, ensuring high sensitivity for the detection of Staphylococcus aureus (S. aureus). Moreover, the assemble SERS probe exhibits the catalytic function of peroxidase (POD), enabling the catalysis of 3,3 ',5,5 '-tetramethylbenzidine (TMB) for colorimetric detection. Additionally, we prepared lectin-functionalized magnetic nanoparticles (F-MNPs-ConA) that demonstrate superior adsorption capabilities towards S. aureus, achieving an impressive adsorption value of up to 98.62%. The F-MNPs-ConA/S. aureus/AuNSs@PB@Ag-Apt sandwich structure constructed by the above SERS probe and magnetic nanoparticles achieves highly sensitive detection of S. aureus. The detection range is 1 x 10(0) similar to 1 x 10(8) CFU.mL(-1), and the detection limit (LOD) is 1 CFU.mL(-1). Notably, this method can be integrated into smartphones, facilitating rapid and on-site detection of S. aureus. Compared with similar biosensors, this biosensor offers distinct advantages, including a wide detection range and a low detection limit. The reliability of the biosensor was confirmed by its application in milk, where the recovery ranged from 93.66 to 120.8%. The dual-mode SERS/colorimetric detection, non-interfering nature, magnetic enrichment, and reusability of the biosensor make it a promising tool for point-of-care testing (POCT).