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Immunoassay has the advantages of high sensitivity, high specificity, and simple operation, and has been widely used in the detection of mycotoxins. For several years, time-resolved fluorescence immunochromatography (TRFIA) paper-based sensors have attracted much attention as a simple and low-cost field detection technology. However, a traditional TRFIA paper-based sensor is based on antibody labeling, which cannot easily meet the current detection requirements. A second antibody labeling method was used to amplify the fluorescence signal and improve the detection sensitivity. Polystyrene fluorescent microspheres were combined with sheep anti-mouse IgG to prepare fluorescent probes (Eu-IgGs). After the probe fully reacted with the antibody (Eu-IgGs-Abs) in the sample cell, it was deployed on the paper-based sensor using chromatography. Eu-IgGs-Abs that were not bound to the target were captured on the T-line, while those that were bound were captured on the C-line. The paper-based sensor reflected the corresponding fluorescence intensity change. Because a single molecule of the deoxynivalenol antibody could bind to multiple Eu-IgGs, this method could amplify the fluorescence signal intensity on the unit antibody and improve the detection sensitivity. The working standard curve of the sensor was established under the optimum working conditions. It showed the lower limit of detection and higher recovery rate when it was applied to actual samples and compared with other methods. This sensor has the advantages of high sensitivity, good accuracy, and good specificity, saving the amount of antibody consumed and being suitable for rapid field detection of deoxynivalenol.

Background Carbohydrate antigen 724 (CA724) is a sensitive and specific indicator for multiple malignant tumors. The aim of this study was to establish a Eu-time resolved fluorescence immunochromatography (Eu-TRFICO) method for quantitative detection of CA724 in serum. Methods Eu-TRFICO strips were optimized and assembled. The sensitivity, specificity and precision were evaluated using CA724 standard dilutions and matrix serum. Meanwhile, the reference interval, comparison, and sensitivity/specificity were performed using clinical negative/positive gastric cancer serum samples. Results The standard curve equation was y = 9.869 x − 154.12 ( R 2  = 0.993), and the sensitivity was 0.42 U/mL. The common interferents in serum could not affect the quantitative results with low cross-reactivities (all no more than 1.09%). All average recoveries of the intra- and interbatch ranged from 102.38 to 106.40%, and all CVs were below 10%. The reference interval of the healthy subjects was < 4.68 U/mL and the reference interval of the subjects with grade I/II gastric cancer was > 9.54 U/mL. Additionally, a high Pearson r (0.9503) and sensitivity/specificity (92.86%/94.20%) were obtained. Conclusion This study prepared Eu-TRFICO strips with high sensitivity, specificity, precision and satisfactory clinical testing performance, which provides more options for clinical quantitative and convenient testing of CA724.

T-2 is one of the most toxic type A trichothecene mycotoxins produced by several fusarium species, which causes a deep harm to the immune system, liver, kidney and brain cells. It is widely found in cereals, cereal products and animal feed. Consequently, it is very important to establish a rapid, efficient and low-cost method for detecting T-2 toxin. In this study, a time-resolved fluorescent immunotomography (TRFIA) paper-based sensor was established. Sheep anti-mouse IgG can protect monoclonal antibody and amplify fluorescence signal. Polystyrene fluorescent microspheres were combined with sheep anti-mouse IgG to prepare fluorescent probes (IgG@Eu). During the detection process, the target-specific monoclonal antibody binds to fluorescence probe (IgG@Eu) to form a complex (mAb-IgG@Eu), which is then captured by the target substance and fixed on the C line. The uncaptured complex (mAb-IgG@Eu) is fixed on the T line by the original coating. Monoclonal antibody can protect its activity by indirect binding with Eu fluorescent beads (FBS). This labeling method improved the binding ratio between the fluorescent microspheres and the monoclonal antibodies. The results of the test strip were compared with liquid chromatography–mass spectrometry (LC–MS/MS), and showed low test line and high recovery rate. With the outstanding augment response, the limit of detection reached 0.01 ng/mL and a wide linear range from 0.0625 to 50 ng/mL was presented. Experimental results show that the detection limit was 0.052 ng/mL and 0.071 ng/mL in corn substrate and feed substrate. The recoveries were between 95.31 and 119.03%, and the relative standard deviations were less than 6.02%. The method was verified by LC–MS/MS, and the results showed that the method had good accuracy.