Au@Ag@MPBA tags assisted surface-enhanced raman spectroscopy for pathogens detection based on bacteria inhibiting salt-induced aggregation

In this work, a highly structured SERS tags assisted bacteria inhibiting salt-induced aggregation platform was proposed for screening foodborne pathogens. Initially, gold and silver core–shell nanoparticles (Au@Ag NPs) were synthesized by forming an Ag shell on an Au core in situ and employed as SERS substrate. The Au@Ag@MPBA tags were prepared by chemically joining Au@Ag NPs and 4-mercaptophenylboronic acid (4-MPBA) via sulfhydryl groups. 4-MPBA functioned as a bacterial recognition element as well as a Raman reporter molecule. Through the reversible recognition relationship between a boronic acid group of 4-MPBA and bacterial peptidoglycan, multiple types of bacteria were collected by Au@Ag@MPBA tags. Plotting the SERS intensity of the tags against the logarithmic concentration of pathogens (56 ∼ 56 × 105 cfu/mL) revealed an ultra-low detection sensitivity of 16 cfu/mL. Bacteria were determined in real fish samples with satisfactory recoveries (94.26 %∼104.37 %) and validation results (p > 0.05). Thus, the comprehensive bacteria-inhibiting salt-induced aggregation SERS-system offered speedy and accurate pathogenic bacteria screening in actual settings.