Reproducible, shelf-stable, and bioaffinity SERS nanotags inspired by multivariate polyphenolic chemistry for bacterial identification.

Efficient identification of pathogenic bacteria is greatly concerned with microbial food safety and foodborne diseases diagnosis. Surface-enhanced Raman scattering (SERS) tags are among the cutting-edge tools for bioanalysis, but facing troubles in either SERS sensitivity, durability, interfering signals, or universal recognition agents for target bacteria. This work proposed a multivariate scheme enabled by polyphenolic chemistry for the green synthesis, facile stabilization (functionalization), protective encapsulation, and bio-affinitive design of metal-phenolic networks (MPNs)-encapsulated silver SERS nanotags (AgNPs@4-mercaptobenzonitrile@MPNs). With remarkable SERS properties, shelf stability, and bacterial affinity, AgNPs@4-mercaptobenzonitrile@MPNs tags enabled rapid, reproducible, and interference-free SERS detection of two representative foodborne pathogens (i.e., E. coli O157: H7 and S. aureus) in the assistance of an aptamer-labelled magnetic probe, reaching good sensitivity and selectivity. Moreover, this SERS biosensor worked well in real food samples, manifesting the potential of polyphenolic chemistry in the customization of bio-affinitive SERS nanotags for food safety detection.