The difference between chemiluminescence immunity, fluorescence immunity, and colloidal gold immunity

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In the field of in vitro diagnostics, there are many immunoassay techniques. The commonly used ones are chemiluminescence immunoassay, fluorescence immunoassay, and colloidal gold immunoassay. What is the difference between these immunoassay techniques?


In terms of immunoassay, chemiluminescence immunity and other immunity are the same, they are all detected by the specific immune response of the combination of antigen and antibody, but the antigen or antibody label is different (usually labeled antibody), which causes The difference in detection methods, sensitivity and anti-interference are also different.


Acridinium Ester


The difference between labeled signals:

The chemiluminescent marker signal is the luminescent reagents acridinium ester, luminol, AMPPD, acridinium ester is used as both a label and a signal, and luminol is usually used as a signal, and the enzyme HRP that catalyzes the reaction is used as a label; colloid The signal of gold is nano-gold particles in the diameter range of 1-100nm, usually 10-25nm, usually with an absorption peak at 520nm, so red colloidal silver and colloidal carbon can also be classified as this type; fluorescence chromatography As the name implies, the signal substance is a fluorescent substance, which can emit corresponding fluorescence when given suitable excitation light, and different fluorescences show different colors.


The difference in marking principle:

Chemiluminescence immunity and fluorescence immunity are usually chemically coupled with antibodies, such as acridinium ester or fluorescein linked to primary amino groups via NHS groups or through EDCI condensation. The labeled conjugate is stable and resists the influence of the matrix to a greater extent. The specificity is better; while the colloidal gold and the antibody are coupled through electrostatic adsorption, which is easily affected by the matrix in the sample, and it will be affected by excessive acid, alkali, and salt.


The difference in sensitivity:

Colloidal gold is a visible light color signal. Fluorescence is penetrating light. Therefore, the sensitivity of fluorescence tomography is at least an order of magnitude higher than that of colloidal gold. Chemiluminescence is a direct luminescence, which does not require a light source like the first two. The light source is different. Cause differences in test results. There are many unstable factors in the preparation of colloidal gold, which can only be used for qualitative detection. The stability of fluorescent substances is better, and it is suitable for semi-quantitative detection or basic quantitative detection. Acridine ester chemiluminescence can be used for quantitative detection.


Although there are differences between different immunoassay methods, it does not mean that which one is absolutely good. For example, different wavelengths of fluorescence can display different colors, multiple indicators can be detected at the same time, and the preparation of colloidal gold probes is simple and low in cost. Chemiluminescence immunoassay is relatively advanced and is the mainstream of detection technology development. Therefore, Desheng also focuses on the development of chemiluminescence reagents such as acridinium ester and luminol.