Simple and rapid co-freezing construction of SERS signal probes for the sensitive detection of pathogens

In this study, we proposed a rapid and sensitive surface-enhanced Raman scattering (SERS)-based biosensor for pathogen detection. The biosensor utilized wheat germ agglutinin (WGA)-modified raspberry-like Fe3O4@Au magnetic nanoparticles (RAuMNPs) as capture elements to enrich the target pathogen and used co-freezing aptamer/5,5′-dithiobis-(2-nitrobenzoic acid) (DTNB)/gold nanoparticles (AuNps) tags as the signal source. Compared to conventional AuNps tags, aptamer/DTNB tags manufactured by co-freezing were easy to prepare, highly stable and had a high affinity for the target bacteria. WGA-coated RAuMNPs captured Escherichia coli (E. coli) O157:H7 from real samples, such as human urine, serum, and skimmed milk, within 20 min under optimized conditions. The combined use of the co-freezing SERS tags and RAuMNPs-WGA significantly improved the analytical sensitivity of the proposed SERS platform, enabling detection as low as 8 cells/mL of target bacteria with a linear range of 10 to 106 cells/mL. Furthermore, the platform successfully detected DNA from difficult-to-culture or slow-growing pathogens, such as Mycobacterium tuberculosis. Overall, this sensitive and fast SERS platform has promising potential for accurate and efficient identification of pathogenic bacteria from cultures and various samples.