Direct chemiluminescence immunoassays chemiluminescent molecules

Antibody molecules have no inherent characteristic that facilitates their direct detection in immunoassays. A second important step in developing a successful immunoassay, therefore, involves the incorporation of a suitable marker . The marker serves to facilitate the rapid detection and quantification of antibody-antigen binding. Earlier immunoassay systems used radioactive labels as a marker (radioimmunoassay RIA) although immunoassay systems using enzymes (enzyme immunoassays EIA) subsequently have come to the fore. Yet additional immunoassay systems use alternative markers including fluorescent or chemiluminescent tags. 

Two-site immunometric or sandwich assays that made use of two or more antibodies directed at different parts of the PRL molecule were next to be developed. As with other two-site IRMA assays, the capture antibody is attached to a solid phase separation system and the second or signal antibody is labeled with a detection molecule (e.g., radio-isotope, enzyme,fluorophor, or chemiluminescence tag ). In some assays, the capture antibody is attached to the wall of test tubes, plastic beads, microtiter plates, ferromagnetic particles, or glass-fiber paper. Other assays have used the strep-avidin approach that couples biotin to the signal antibody with avidin linked to a solid phase. Most of the current immunometric assays for PRL have been adapted to fully automated immunoassay systems. Compared with the older traditional RIA methods, these automated immunometric assays for PRL generally achieve lower detection limits (0.2 to 1.0 ig/L) and improved precision (interlaboratory coefficients of variation of <8% at all concentrations), and have superior specificity (<0.05% crossreactivity with GH). 

---