In-situ, ultrasensitive, and specific detection of malachite green in fishes with handheld Raman spectrometer

Abstract

The presence of malachite green (MG) residues in aquatic products poses a significant threat to food safety. While label-free Surface-enhanced Raman scattering (SERS) technologies have been developed for detecting malachite green, it faces the challenge of limited sensitivity and specificity. A new immunochromatographic assay (ICA) based on SERS method using Au-DTNB@Ag-mAb as an immunoprobe was established for the in-situ, specific, and ultrasensitive detection of MG in fish samples. The immunoprobe was produced by connecting the Raman reporter 5,5′-dithiobis-(2-nitrobenzoic acid) (DTNB) between the Au-core and Ag-shell and binding the MG monoclonal antibody (mAb) on the surface of the Au-DTNB@Ag NPs. The SERS signal of DTNB on the test line of the ICA strip has been recorded to determine MG quantitatively. The method demonstrated high specificity for MG detection, with a limit of detection as low as 0.1 pg/mL. The SERS-ICA confirmed outstanding results for analyzing actual fish samples with recoveries of 70.93–93.90 %. The study indicated that the SERS-ICA method was able to directly detect MG with excellent sensitivity, specificity, and accuracy, and could serve as a potent technique for in-situ analyzing other harmful substances in foods.