A surface-enhanced Raman scattering-based lateral flow immunosensor for colistin in raw milk

A surface-enhanced Raman scattering (SERS)-based lateral flow immunosensor was created to identify colistin in milk. The Raman reporter 5,5-dithiobis-2-nitrobenzoic acid (DTNB) was used to label gold nanoparticles, and then anti-colistin monoclonal antibody (mAb) was attached. The size of the gold nanoparticles in the SERS nanoprobe was optimized, and the amount of DTNB and mAb, the change in hydrodynamic size, zeta potential, and the surface plasmon resonance band were also monitored in the preparation process. The SERS nanoprobe was then applied to a lateral flow strip followed by Raman signal readout for the quantitative determination of colistin with high sensitivity. The limits of detection of this assay were 0.10 ng/mL for colistin in milk, which was far below the previously reported value that was obtained with the ELISA method and the maximum residue limit set by the European Union. The spiking experiment showed high accuracy for this SERS-based immunosensing assay, with a recovery of 88.1%–112.7% and satisfactory assay precision with a standard deviation below 15%. Furthermore, this assay also has the advantage of rapidity, with an assay time less than 20 min. Therefore, these results demonstrate that this SERS-based lateral flow immunosensor is promising for use in the rapid monitoring of colistin in milk.