A universal SERS-label immunoassay for pathogen bacteria detection based on Fe3O4@Au-aptamer separation and antibody-protein A orientation recognition

Rapid, reliable and sensitive detection methods for pathogenic bacteria are strongly demanded. Herein, we proposed a magnetically assisted surface enhanced Raman scattering (SERS)-label immunoassay for the sensitive detection of bacteria by using a universal approach based on free antibody labelling and staphylococcus proteins A (PA)-SERS tags orientation recognition. The SERS biosensor consists of two functional nanomaterials: aptamer-conjugated Fe3O4@Au magnetic nanoparticles (MNPs) as magnetic SERS platform for pathogen enrichment and PA modified-SERS tags (Au@DTNB@PA) as a universal probe for target bacteria quantitative detection. After target bacteria enriched, free antibody was used to specific marking target bacteria and provided numerous Fc fragment, which can guide the PA-SERS tags orientation-dependent binding. With this strategy, Fe3O4@Au/bacteria/SERS tags sandwich immunocomplexes for most bacteria (expect several species of Staphylococcus) were easy constructed. The limits of detection (LODs) of the proposed assay were found to be 10, 10, and 25 cells/mL for three common pathogens Escherichia coli (E. coli), Listeria monocytogenes (L. mono), and Salmonella typhimurium (S. typhi), respectively, in real food samples. The universal method also exhibits the advantages of rapid, robust, and easy to operate, suggesting its great potential for food safety monitoring and infectious diseases diagnosis. [Display omitted] •A SERS biosensor for sensitive and universal detection of bacteria was proposed.•Fe3O4@Au-aptamer was used to specifically capture bacteria.•PA modified-SERS tags and free antibody labeling were combined to achieve orientation binding.•The LODs for three common pathogens were as low as 10–25 cells/mL.