Highly sensitive SERS detection for Aflatoxin B1 and Ochratoxin A based on aptamer-functionalized photonic crystal microsphere array

A highly sensitive surface-enhanced Raman spectroscopy (SERS) aptasensor for multiplex mycotoxins detection was developed based on aptamer-functionalized photonic microsphere array. Gold nanoparticles (AuNPs) were grafted covalently onto the silica photonic crystal microsphere (SPCM) to fabricate the SERS active substrate, on which the near-field enhancement can reach to 20 times analyzed by the simulation electric field distribution. Two dyes of 5,5 '-dithiobis (2-nitrobenzoic acid) (DTNB) and nile blue A (NBA) were employed to make the SERS nanotags on AuNPs that were modified with corresponding anti-aptamer sequences. A SERS assay system was established based on the competitive reaction between the anti-aptamer on SERS nanotags and the target mycotoxin towards the aptamer on SPCM. The developed method showed a linear relationship in the range of 0.01-100 ng/mL for aflatoxin B-1 (AFB(1)) and 0.001-10 ng/mL for ochratoxin A (OTA), and a low limit of detection of 0.36 pg/mL for AFB(1) and 0.034 pg/mL for OTA. The accuracy of such method was confirmed by its good recovery ratio and high repeatability, and further verified by the classic enzyme-linked immunosorbent assay using naturally mycotoxins contaminated edible samples. The established method has a great application potential for screening mycotoxins rapidly with high sensitivity, low-cost and high throughput in the fields of food and traditional Chinese herb.