Due to the complex characteristics of food matrix, false positives may occur when using traditional methods to detect aflatoxin B1 (AFB1). In this paper, we utilize the advantages of closed bipolar electrode (BPE) that can effectively avoid the impact of complex food matrices on signal collection, and design a biosensor based on immune competition to detect highly toxic AFB1. The biosensor uses cathode of closed BPE as a functional sensing interface and anode as a signal collection interface. On the functional sensing interface, AFB1 connects to the monoclonal antibody at the top of DNA tetrahedron structure. Under the action of horseradish peroxidase (HRP), 4-chloro-1-naphthol (4-CN) is catalyzed by hydrogen peroxide (H 2 O 2 ) to generate precipitations (4-CD). AFB1 competes with HRP-AFB1 to bind monoclonal antibody, resulting in a decrease in the content of HRP involved in catalytic oxidation reactions and a synchronous reduction in precipitations produced, causing an increase in the intensity of [Ru(bpy) 3 ] 2+ /TPA system electrochemiluminescence (ECL) on the BPE anode. Analysis shows that the relative deviation between the detection results and ELISA is between −4.5 and 9.8%, and there is no significant difference in the performance of the two in detecting AFB1. The BPE-ECL sensor exhibits high sensitivity and specificity in detecting AFB1, with a linear range of 0.01–40 ng mL −1 and a detection limit of 3 pg mL −1 . In the future, it can be applied to the detection of other toxins, with broad application prospects.
As an organochlorine pesticide, procymidone has become an increasing serious problem in vegetables in recent years. In order to solve a series of problems such as low sensitivity of the immunological methods, a time-resolved fluorescent immunoassay strip (TRFIAS) was developed with low limit of detection (LOD). Based on the principle of antigen-antibody immune competition, TRFIAS could detect procymidone in vegetables. After the targets being added, the samples were incubated at 37°C for 10 min. TRFIAS was observed under a UV lamp of 365 nm. The results were processed by ImageJ software to complete the qualitative and quantitative analysis of TRFIAS. Under the optimal working conditions, a linear range of TRFIAS was 5–250 ng/mL with a LOD of 0.33 ng/mL and a visual limit of detection (VDL) of 50 ng/mL. And the TRFIAS had good specificity, precision and accuracy. Comparing the results of TRFIAS with those of ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), the two assays were in good agreement. Therefore, TRFIAS has the advantages of high sensitivity, high specificity, simple operation and relatively short assay time. Meanwhile, it shows absolutely great advantages in both quantitative and qualitative analysis.
危险品化学品经营许可证（带存储）