Surface-enhanced Raman spectroscopy (SERS)-based immunochromatographic assay (ICA) for the simultaneous detection of two pyrethroid pesticides

Here we describe a surface-enhanced Raman scattering (SERS)-based immunochromatographic assay (ICA) method for the dual detection of two pyrethroid pesticides cypermethrin and esfenvalerate. In the proposed ICA-SERS methods, antibody conjugated gold nanoparticles (AuNPs) were used as the SERS substrate while fluorescence tags labeled on AuNPs were used as the Raman reporters for SERS. Through the immuno-specific combination of antigen and antibody, Raman reporter labeled AuNPs were immobilized on the test line of the ICA strip and facilitated the SERS measurement. And by immobilizing two test lines designed for the detection of two pesticides, a simultaneous dual detection was accomplished. The LODs of the ICA-SERS system was 2.3 × 10−4 and 2.6 × 10-5 ng/mL for cypermethrin and esfenvalerate, respectively. The sensitivity was 3 to 4 times higher than ELISA and fluorescent-based ICA methods using the same indirect competitive immunoassay methods. For the three types of samples (tap water, river water, and milk), the recoveries ranged from 94.9% to 112%, with RSD values ranged from 1.3% to 13.5%. The research reveals that this ICA-SERS method possesses high specificity, sensitivity, and reproducibility, and can be reliably used to detect dual pesticides in real samples. An R Shiny-based application 2plex-speclysis was built and used for all the data analyses in this paper. The application was designed to incorporate all the analyses including spectral preprocessing, performance evaluation, and PCA analysis, and make the spectral analysis accessible for people without programming experience.