Add on Dual-Modal Optical Immunoassay by Plasmonic Metal NP-Semiconductor Composites

Staphylococcus aureus enterotoxins (SEs, involving SEA, SEB, SEC, SED, and SEE) are considered to be the common toxins causing food poisoning and are not allowed to be detected in food. Accurate and anti-interfering SE detection in a complex food matrix is urgently required for food safety. Dual-modal optical sensors are able to avoid mutual interference of optical signals and possess the advantages of high accuracy and sensitivity. Herein, Au nanobipyramids (Au NBPs) and persistent luminescence ZnGeGa0:Cr,Er,Yb nanoparticle (ZGGO NP) nanocomposites are fabricated using the SEC antibody/antigen as templates, which display enhanced persistent luminescence (PL) and surface-enhanced Raman scattering (SERS) strength. The enhanced PL of Au NBP-ZGGO NP nanocomposites is ascribed to plasmon-enhanced radiative transitions. It is first found that ZGGO NPs display unique upconversion fluorescence, which can be absorbed by Au NBPs and that they largely excite the intensive electromagnetic field for SERS enhancement. Dual-model optical immunoassay achieved anti-interfering and specific SEC detection with a limit of detection of 7.5 pg/mL for the PL signal and 8.9 pg/mL for the SERS signal in the range of 10 pg/mL-100 ng/mL. Depending on the plasmon-enhanced PL mechanism and upconversion fluorescenceenhanced SERS principle, plasmonic NP-semiconductor composites show potential prospects in the establishment of multimodal optical biosensors for the quantitative and accurate evaluation of analytes in a complex food matrix.

Automated summary

This study successfully achieved accurate and sensitive detection of Staphylococcus aureus enterotoxin SEC in complex food samples using a novel dual-modal optical sensor. The nanocomposites fabricated with gold nanobipyramids and persistent luminescence nanoparticles exhibited enhanced persistent luminescence and Raman scattering signals. By utilizing the plasmon-enhanced PL mechanism and upconversion fluorescence-enhanced SERS principle, the plasmonic NP-semiconductor composites hold potential in establishing multimodal optical biosensors for quantitative and accurate evaluation of analytes in complex food matrices.