Gd2O3:Eu3+ nanoparticle-based magnetic relaxation switch/fluorescence dual-mode immunoassays for aflatoxin B1 in grain

Breakthroughs in high sensitivity and good anti-interference is crucial for achieving high-efficient detection of trace hazards in food. Here, we report on the development of a magnetic relaxation switch (MRS)/fluorescence (FL) dual-mode sensor based on Gd2O3:Eu3+ nanoparticles for the detection of aflatoxin B1 (AFB1) in grain. With the doping of Eu3+ on Gd2O3, it is interesting that the resulted Gd2O3:Eu3+ exhibit significant concentration-dependent MRS/FL responses, thus is capable to be functioned as a dual-mode signal probe for AFB1. In addition, the AFB1 monoclonal antibody was conjugated with magnetic beads (MB) to act as capture probes to separate and concentrate the targets. Based on the specific immunologic recognition, excellent MRS/FL responses of Gd2O3:Eu3+, and the magnetic separation of MB, a dual-mode Sandwich immunoassay was constructed to detect AFB1 with high sensitivity, strong anti-interference, and involves simple preprocessing steps; Under optimal conditions, the detection limits of the MRS and FL modes by the immunoassay for AFB1 are 0.142 and 0.049 μg/kg, respectively. The developed dual-mode immunoassay can be used to detect AFB1 in corn and wheat samples with consistent results from high-performance liquid chromatography. The designed strategy reveals good performance in detecting AFB1, which can extend also to other hazards detection with interest not only for food safety but also environmental monitoring and diagnostics.