Rapid detection of zearalenone in cereals using La3+-doped upconversion nanoparticles-based immunochromatographic assay

A novel fluorescent immunochromatographic assay (ICA) with excellent specificity and sensitivity for evaluating trace residues of zearalenone (ZEN) in cereal samples was successfully developed. La3+-doped upconversion nanoparticles (UCNPs) were assessed as antibody labels, following optimization of doping ratios. Our results indicated that 20% La3+-doped UCNPs had superior morphological structure and fluorescence characteristics, making them the optimal UCNPs. After labeling 20% La3+-doped UCNPs with ZEN monoclonal antibodies (mAbs), optimal polyacrylic acid amount, coupled mAbs amount, detection time, and fluorescent immunoprobe concentrations were determined as 2.0 mL, 20 μg, 10 min, and 8 mg/mL, respectively. Under optimized detection conditions, the limit of detection (LOD) for ZEN standard solutions was 0.25 ng/mL with coefficients of variation (CVs) ＜ 8.67% and a high linear correlation (R2 = 0.9944). Furthermore, specificity analysis demonstrated that prepared test strips were highly specific for the target mycotoxin. The LODs of ZEN in wheat and maize were both 0.5 μg/kg in spiking recovery experiments, and the recoveries were 87.65%–99.26% and 84.12%–95.12% with the CVs being 1.29%–7.14% and 4.03%–9.01%, respectively, confirming that the optimal UCNPs-ICA was efficient, straightforward, and suitable for rapid on-site screening of ZEN in cereals.