Colorimetric-SERS dual-mode aptasensor for Staphylococcus aureus based on MnO 2 @AuNPs oxidase-like activity

The nanozyme-linked aptamer-sorbent assay (NLASA) is a rapid way to screen and characterize aptamer binding to targets. In this paper, a MnO 2 @AuNPs@aptamer (Apt) based NLASA coupled with colorimetric-SERS dualmode for Staphylococcus aureus ( S. aureus ) detection is presented. Cu,Fe-CDs were used as the reducing agent to synthesize MnO 2 and gold nanoparticles (AuNPs). Then, they were fabricated to obtain MnO 2 @AuNPs with oxidase (OXD)-like and SERS activities. The S. aureus aptamer was conjugated to MnO 2 @AuNPs and enhanced the OXD-like activity, which realized the specific capture of S. aureus in food matrices. In addition, S. aureus improves the oxidation of 2,2 ' -azino-bis (3-ethylbenzthiazoline-6-sulfonic acid (ABTS) but inhibits 3,3 ' ,5,5 ' -tet- ramethylbenzidine (TMB) to generate Raman-active oxTMB with MnO 2 @AuNPs@Apt. This sensor was used for detections of S. aureus in a concentration ranged from 10 1 to 10 7 CFU/mL with a detection limit of 0.926 CFU/mL (colorimetric) and 1.561 CFU/mL (SERS), and the recovery is 85% -105% in real samples.