A highly sensitive and reproducible multiplex mycotoxin SERS array based on AuNPs-loaded inverse opal silica photonic crystal microsphere

A highly sensitive and reproducible multiplex mycotoxin SERS array has been established based on gold nanoparticles (AuNPs)-loaded inverse opal silica photonic crystal microsphere (SIPCM). Three types of Raman nanotags were synthesized by covalently grafting different antibodies and non-covalently loading different organic dyes onto the AuNPs for coding corresponding mycotoxins. To enhance Raman signal, AuNPs were loaded on the surface of SIPCM to create hot-spots once the Raman nanotags came closely. The maximal electric field enhancing effect in SIPCM with AuNP dimer could reach to 8 times. The assay principle was based on the competition immunoassay between the mycotoxins in sample and the artificial antigens immobilized on the surface of SIPCM. The three Raman nanotags could be integrated into an array to qualitatively and quantitatively detect multiplex mycotoxins in a sample. Such SERS-based assay displayed wide linear detection ranges of 0.001–10 ng/mL for ochratoxin A (OTA), 0.001–10 ng/mL for fumonisin B1 (FB1), and 0.1–1000 ng/mL for deoxynivalenol (DON), and low limits of detection (LOD) of 2.46 pg/mL for OTA, 0.20 pg/mL for FB1, and 68.98 pg/mL for DON. The recovery rates of the new method were measured to be 77.68–104.69% for OTA, 76.39–117.73% for FB1, and 70.95–113.16% for DON, in agreement with that of the classical ELISA method. The SERS-based method shows obvious advantages over fluorescence label or enzyme catalytic chemiluminescence methods, having a great application potential in rapidly screening multiplex mycotoxins in real samples.