FPBA-modified magnetic nanoparticles combined with Au@AgNPs for label-free SERS detection of foodborne pathogens in milk

We report a low-cost and highly sensitive label-free SERS biosensor for pathogen detection. Herein, this study prepared 4-formylphenylboric acid (FPBA) functionalized magnetic nanoparticles to adsorb pathogenic bacteria through boric acid affinity principle, and used aptamer modified Au@AgNPs as SERS substrate to specifically combine with pathogenic bacteria to form a sandwich structure. The pathogenic bacteria were detected by portable Raman spectrometer for SERS detection, and the fingerprint signals of pathogenic bacteria were analyzed by principal component analysis (PCA) to achieve the purpose of classification and identification of pathogenic bacteria. Under the optimized conditions, the SERS detection of Staphylococcus aureus (S. aureus) was 102 - 106 CFU/mL (R2 = 0.9925), and the limit of detection (LOD) was 34 CFU/mL. The linear range of Escherichia coli (E. coli) showed a good linear relationship in the range of 102 - 106 CFU/mL (R2 = 0.9993), and the LOD was 18 CFU/mL. The whole detection process was used the portable Raman spectrometer, which makes it suitable for the application of point-of-care testing (POCT).

Automated summary

We present a cost-effective and highly sensitive label-free SERS biosensor for pathogen detection. The biosensor utilizes 4-formylphenylboric acid functionalized magnetic nanoparticles to adsorb pathogenic bacteria and aptamer modified Au@AgNPs as SERS substrate for specific binding. The detection of pathogenic bacteria is achieved using a portable Raman spectrometer and analyzed through principal component analysis (PCA). The SERS detection limit for Staphylococcus aureus is 34 CFU/mL, and the linear range for Escherichia coli is 102-106 CFU/mL.