The scheme of immunochromatographic competitive analysis with "external" specific antibodies is offered for the first time. The test strip includes all the necessary components for analysis (membranes, protein antigen conjugates, colored nanoparticles), except specific free unconjugated antibodies that are transferred to the buffer used for sample dilution. Thus, the concentrations of the antibodies and markers can be chosen independently, and dilution of the sample with buffer (a routine procedure for any immunochromatographic test) ensures pre-incubation of the antibodies with the sample. Both factors increase the sensitivity of the test. The proposed scheme has been proven to be effective for the determination of deoxynivalenol and T-2 toxin; detection limits of 500pg/mL and 50pg/mL, respectively, were achieved. This is an order of magnitude lower than the limits of detection of traditional tests using the same reagents. The analysis was conducted in water-organic extracts (20% methanol); the duration of the analysis is 10min (it's the same time as for a traditional test). The proposed approach is universal, and it can be used to detect a variety of compounds.
Keywords: Gold nanoparticles; Immunochromatography; Immunosensor; Indirect labeling; Sensitivity enhancement; Test strip.
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