Application of Gold Nanorods in Combination with Surface-Enhanced Raman Spectroscopy for Immunochromatographic Determination of Ochratoxin A

The aim of the study was to increase the sensitivity of immunochromatographic assay (ICA), achieved using gold nanorods modified with 5,5'-dithiobis-(2-nitrobenzoic acid). The resulting nanomarker makes it possible to quantify the target analyte using colorimetry and surface-enhanced Raman spectroscopy (SERS). One of the widespread mycotoxins, ochratoxin A (OTA), was chosen as the object of study. After functionalization of gold nanorods with antispecies antibodies, the SERS-active tag was used to detect immune complexes formed in the analytical zone as a result of the competitive interaction between free OTA and the hapten-protein conjugate for the binding sites of specific antibodies. After immunochromatographic assay, SERS intensity of 5,5'-dithiobis-(2-nitrobenzoic acid) was measured. Under optimized conditions, the detection limit of OTA in the colorimetric detection mode was 1.7 ng/mL, and when recording ICA results using SERS, it decreased to 33 pg/mL.