Immunochromatographic Test Systems using Anti-Species Antibodies–Colloidal Gold Conjugate: Their Features and Benefits on the Example of Ochratoxin A Detection

The traditional immunochromatographic assay using a conjugate of gold nanoparticles with specific ochratoxin A (OTA) antibodies and a new type of assay with indirect labeling using a combination of free antibodies and a conjugate of gold nanoparticles with anti-species antibodies were compared using the example of OTA detection. In the proposed assay, specific antibodies are included in the sample dilution buffer, which increases the duration of their interaction with the antigen, while a conjugate of anti-species antibodies with the marker is applied to the test strip. The assay was approbated for OTA detection in maize extracts. Transition to indirect labeling was shown to reduce the OTA detection limit by two orders of magnitude up to 0.12 ng/mL. The causes of this improvement are discussed. The high sensitivity of immunochromatography with indirect labeling makes it a promising approach for detection of various antigens with low molecular weight.