Immunochromatographic assay

Principal of immunochromatography kit

Principal of immunochromatography is the same as ELISA sandwich method, only difference is in that immunological reaction is carried out on the chromato- graphic paper by capillary action.   For this system, two kinds of specific antibodies against antigen are used. One of the antibodies is immobilized on the chromatographic paper, and the other is labeled with colloidal gold and infiltrated into sample pad. An imunochromatographic unit is completed by attaching the sample pad at the end of the membrane.

When the liquid sample is dropped on the sample pad, the antigen in the sample forms an immunocomplex with the antibody labeled with colloidal gold. Its complex moves along with the liquid sample, and makes a contact with the antibody immobilized on the membrane, followed by forming an immuno- complex with the immobilized antibody, resulting in generating a colored red purple line.

Appearance of red purple line on the membrane indicates the presence of antigen of interest in the sample. Since the liquid of the sample migrates through the membrane very fast, it makes it possible to detect the presence or absence of antigen within 15 minutes.

Principle of immunochromatography kit