RESUMO
To ensure food safety and prevent the toxic effects of paclobutrazol (PBZ) and carbofuran (CAR) on humans, a sensitive and rapid method for the detection of PBZ and CAR in fruits and vegetables is required. Herein, a highly sensitive PBZ monoclonal antibody (PBZ mAb) and CAR monoclonal antibody (CAR mAb) with half-inhibitory concentrations (IC50) at 0.77 and 0.82 ng mL-1 were prepared, respectively. We proposed a novel dual-color immunochromatographic assay (ICA) with two test lines (T1 and T2) and an independent control line (C) based on chrysanthemum-like Au@Polydopamine (AuNC@PDA) and colloidal gold (AuNPs) for the simultaneous and sensitive detection of PBZ and CAR with naked-eye detection limits of 10 and 5 µg kg-1, respectively. The limits of detection (LOD) for PBZ and CAR were 0.117 and 0.087 µg kg-1 in orange, 0.109 and 0.056 µg kg-1 in grape, and 0.131 and 0.094 µg kg-1 in cabbage mustard, respectively. The average recoveries of PBZ and CAR in orange, grape, and cabbage mustard were 97.86-102.83%, with coefficients of variation from 8.94 to 11.05. The detection results of this method for 30 samples (orange, grapes, and cabbage mustard) agreed well with those of liquid chromatography-tandem mass spectrometry. The novel dual-color ICA was sensitive, rapid, and accurate for the simultaneous detection of PBZ and CAR in real samples.
RESUMO
Conventional enzyme-linked immunosorbent assay (ELISA) is commonly used for Ochratoxin A (OTA) screening, but it is limited by low sensitivity and harmful competing antigens of enzyme-OTA conjugates. Herein, a bifunctional M13 bacteriophage with OTA mimotopes fused on the p3 protein and biotin modified on major p8 proteins was introduced as an eco-friendly competing antigen and enzyme container for enhanced sensitivity. Mercaptopropionic acid-modified quantum dots (MPA-QDs), which are extremely sensitive to hydrogen peroxide, were chosen as fluorescent signal transducers that could manifest glucose oxidase-induced fluorescence quenching in the presence of glucose. On these bases, a highly sensitive and eco-friendly fluorescent immunoassay for OTA sensing was developed. Under optimized conditions, the proposed method demonstrates a good linear detection of OTA from 4.8 to 625 pg/mL and a limit of detection (LOD) of 5.39 pg/mL. The LOD is approximately 26-fold lower than that of a conventional horse radish peroxidase (HRP) based ELISA and six-fold lower than that of a GOx-OTA conjugate-based fluorescent ELISA. The proposed method also shows great specificity and accepted accuracy for analyzing OTA in real corn samples. The detection results are highly consistent with those obtained using the ultra-performance liquid chromatography-fluorescence detection method, indicating the high reliability of the proposed method for OTA detection. In conclusion, the proposed method is an excellent OTA screening platform over a conventional ELISA and can be easily extended for sensing other analytes by altering specific mimic peptide sequences in phages.
RESUMO
Sulfamethazine (SMZ) as a broad antibiotic is widely used in livestock and poultry. However, the abuse of SMZ in livestock feed can lead to SMZ residues in food and the resistance of bacteria to drugs. Thus, a method for the detection of SMZ in food is urgently needed. In this study, quantum dot (QD) nanobeads (QBs) were synthesized by encapsulating CdSe/ZnS QDs using a microemulsion technique. The prepared QBs as signal probes were applied in lateral flow immunoassay (LFIA) for the detection of SMZ in chicken and milk. Our proposed method had limits of detection of 0.1138-0.0955 ng/mL and corresponding linear ranges of 0.2-12.5, 0.1-15 ng/mL in chicken and milk samples, respectively. The recovery of LFIA for the detection of SMZ was 80.9-109.4% and 84-101.6% in chicken and milk samples, respectively. Overall, the developed QBs-LFIA had high reliability and excellent potential for rapid and sensitive screening of SMZ in food.