Direct chemiluminescence

The immunoassay method in which the chemiluminescent agent is directly labeled to the antibody or antigen is called chemiluminescent immunoassay. Direct chemiluminescent agents do not require the catalytic action of enzymes in the luminescent immunoassay process and directly participate in the luminescent reaction. They have a unique group that produces luminescence in the chemical structure and can directly label antigens or antibodies. The common direct chemiluminescent markers are acridinium esters and isoluminol.
Direct chemiluminescence is fast and the reagent is stable, but the sensitivity is slightly lower than enzymatic luminescence.

Enzymatic chemiluminescence

Enzymatic chemiluminescent immunoassay is an immunoreaction in which the enzyme labels the antigen or antibody. The enzyme on the reaction complex then acts on the luminescent substrate and emits light under the action of the signal reagent. The luminescent signal tester is used for luminescence measurement. The concentration of the enzyme determines the intensity of the chemiluminescence. HRP and ALP are commonly used marker enzymes, and the luminescent substrates are luminol, AMPPD, etc.

Electrochemiluminescence

When a certain voltage or current is applied to the electrode, a chemical reaction occurs between the products of the click electrochemical reaction and between the products of the click reaction and a component in the solution. When the excited state transitions back to the ground state, energy is released. This process is called electrochemiluminescence (ECL). The main electrochemiluminescent agent in this method is terpyridine ruthenium.

Comparison of three chemiluminescence methods: