Fluorescent lateral flow immunoassay for highly sensitive detection of eight anticoagulant rodenticides based on cadmium-free quantum dot-encapsulated nanospheres

A method for the rapid, sensitive, and eco-friendly detection of anticoagulant rodenticides (ARs) in emergency clinics and food samples with point-of-care (POC) assay is highly demanded. The gold nanoparticles and cadmium-based quantum dots (QDs) used as probe in POC testing usually suffer from low sensitivity and high toxicity. Hence, here, we synthesized hydrophilic QDs-based polystyrene nanospheres (QNs) by encapsulating cadmium-free and oleylamine-coated InP/ZnS QDs into polystyrene nanospheres via a facile swelling-evaporation strategy. A lateral flow immunoassay (LFIA) adopted the QNs as probes was proposed to detect eight ARs, achieving quantitative limits of detection from 0.01-2.0 mu g/L and visual limits of detection from 0.16-32.0 mu g/L for warfarin, coumachlor, coumafuryl, bromadiolone, difenacoum, coumatetralyl, diphacinone and chlorophacinone. The accuracy and precision of the QNs-based LFIA were evaluated by ARs-spiked wheat, human serum and urine, and acceptable recoveries were obtained. The sensitivity of QNs-based LFIA was 2.5-6.25 times better than that of the gold nanoparticles-based LFIA. The QNs-based LFIA was applied to clinical human serum and showed good correlation with ultraperformance liquid chromatography-tandem mass spectrometry. In summary, the QNs-based LFIA provides a rapid, sensitive, and quantitative POC testing method of ARs for poisoning diagnosis and food analysis.