Highly sensitive SERS-based lateral flow immunoassay of fipronil using bimetallic Au@Ag@Ag nanorods

A bimetallic core-shell-shell nanorods structure with gap-embedded Raman reporter 5,5'-dithio-bis-(2-nitrobenzoic acid) (DTNB) was developed and applied as a SERS-active nanotag in surface-enhanced Raman scattering lateral flow immunoassay (SERS-LFIA) of the insecticide fipronil. Due to the strong SERS signal of the Au^DTNB@Ag^DTNB@AgNRods, fipronil is detected with extremely low detection limit of 4.6 pg/mL. To the best of our knowledge, the proposed technique is the first SERS-LFIA of fipronil, proven to be effective in the selective determination of the target analyte and capable of detecting fipronil in a matrix of food samples (cucumber and apple juice) with recoveries of 97.0-117.0%. Moreover, the applied functionalization of the SERS nanotag with anti-species antibodies has provided a versatile immunoprobe that could improve performance of different LFIAs.