Enhanced immunochromatographic assay of tetracycline using intrinsic peroxidase-like activity of gold nanoparticles.

Tetracycline (TC) is a broad-spectrum antibiotic widely used in animal husbandry that may contaminate foodstuffs. In this study, a highly sensitive immunochromatographic assay (ICA) for TC was developed and applied to test meat samples. The assay utilized an indirect competitive format, with conjugates of anti-species antibodies and gold nanoparticles (GNPs) used to label specific immune complexes. The intrinsic peroxidase-like activity of GNPs was leveraged to enhance assay sensitivity. GNPs catalyzed substrate oxidation, resulting in a colored product that increased the brightness of the analytical zones on the test strips. An optimal substrate solution based on 3,3',5,5'-tetramethylbenzidine was selected. The limit of TC detection reached was 0.03 ng/mL. The assay duration was 18 min, including the catalytic reaction. Two meat sample preparation procedures were compared. The developed ICA demonstrated TC recoveries in beef ranging from 92 to 113%. The simple, rapid, and sensitive TC detection, combined with the use of GNP labels well-suited to manufacturing technologies, makes the developed ICA an efficient tool for mass screening tests of food products.