A Novel Multiplex Mycotoxin Surface-Enhanced Raman Spectroscopy Immunoassay Using Functional Gold Nanotags on a Silica Photonic Crystal Microsphere Biochip

A novel multiplex mycotoxin surface-enhanced Raman spectroscopy (SERS) immunoassay was established for the first time on different artificial antigen-modified silica photonic crystal microspheres (SPCMs), which can be integrated into a biochip array to achieve multiplex detection using corresponding antibody-functionalized gold nanoparticles (AuNPs) as the SERS nanotag. The unique optical structure of SPCMs is helpful to find the detection spots easily, accommodate a large amount of probe molecules, and enhance the Raman signal intensity. Such enhancement was confirmed by the simulation result, showing the electric field enhancing effect in SPCMs with AuNPs being 7 times. A competitive SERS immunoassay was established using antigenmodified SPCMs and mycotoxins to compete for binding antibody-functionalized SERS nanotags, displaying broad linear detection ranges of 0.001-0.1 ng/mL for aflatoxin B-1 (AFB(1)), 0.01-10 ng/mL for ochratoxin A (OTA), and 0.001-0.1 ng/mL for zearalenone (ZEN) and low detection limits of 0.82 pg/mL for AFB(1), 1.43 pg/mL for OTA, and 1.00 pg/mL for ZEN. In the spiked cereal samples, recovery rates of the method were measured in the range of 70.35-118.04% for the three mycotoxins, which was in agreement with that of the traditional enzyme-linked immunosorbent assay method. The SERS immunoassay for mycotoxin detection also showed high specificity and good repeatability and reproducibility. The new microsphere-based SERS immunoassay biochip only requires a one-step reaction and overcomes the disadvantages of fluorescence and chemiluminescence background signals. The work paves the way for further developing SERS-based microsphere suspension arrays for new targets.

Automated summary

A novel multiplex mycotoxin surface-enhanced Raman spectroscopy (SERS) immunoassay was established using antigen-modified silica photonic crystal microspheres (SPCMs) and gold nanoparticles (AuNPs) for multiplex detection with high sensitivity and good recovery rates. The method exhibited high specificity and repeatability, while overcoming the drawbacks of fluorescence and chemiluminescence background signals.