Ratiometric SERS sensor for sensitive quantification of methicillin-resistant Staphylococcus aureus using Ti3C2@AuNP films and aptamer-based tags

Abstract

Sensitive and rapid detection of drug-resistant bacteria is important in dealing with bacterial infections. Rapid and sensitive identification of methicillin-resistant Staphylococcus aureus (MRSA) was carried out based on a surface enhanced Raman spectroscopy (SERS) sensor with a sandwich structure and ratiometric strategy. The structure uses self-assembled Ti₃C₂@AuNP as substrate, with the modified 4-mercaptobenzoic acid (4-MBA) as an internal standard (IS) molecule and the aptamer as specific capture unit on the substrate. AuNP modified with 5,5’-dithibis (2-nitrobenzoic acid) (DTNB) and streptavidin (SA) were used as SERS tags. Biotin-modified aptamers were further combined with SA to specifically bind the tag to the substrate that captured the bacteria to form the sandwich structure. The structure Ti₃C₂@AuNP@4-MBA/bacteria/Au@DTNB@SA could specifically capture and quantitative analysis MRSA. The intensity ratio (I_DTNB/I_4-MBA) showed good linear relationship with the concentration of MRSA, with a limit of detection (LOD) as low as 10 CFU/mL, and a wide linear range (10–10⁸ CFU/mL). The method has good homogeneity (RSD = 8.29 %), reproducibility (RSD = 6.77 %) and specificity. The strategy also performs well on the actual samples (recovery rate 87.9–96.5 %). Therefore, the proposed SERS sensor can specifically capture and sensitively detect MRSA, with potential applications in food detection and clinical treatment.