Chemiluminescence immunoassay sensitivity

Chemiluminescence immunoassay methods have many applications (Weeks, 1992). Highly sensitive chemiluminescent immunoassays were developed by Tsuji et al. (1989) for determination of enzymes (oxidases, peroxidase, glucose oxidase, P-D-galactosidase) as well as various hormones and drugs in biological fluids (Tsuji et al., 1989). 

Most immunoassays currently employed in the biomedical field are either radioimmunoassays, enzyme immunoassays, or luminescence immunoassays (including fluorescence immunoassays [FIA] and chemiluminescence immunoassays). Although radioimmunoassay is currently the most sensitive of these (10 -10 M concentrations are often detectable), due to the problems inherent to dealing with radioactive materials, such as licensing, radiation hazard, short shelf-life of expensive radioisotopes, the expense of the counting equipment, and the tedium associated with heterogeneous immunoassay, it has fallen, in popularity, behind the non-isotopic methods of analysis. 

Chemiluminescence immunoassay,a technique that has rapidly gained popularity because its sensitivity is comparable to that of radioimmunoassay, is in a sense a variation of FIA. In the 1930s, the first work on chemiluminophores was published, but it was not until the 1980s that chemiluminescence was first tried in immunoassays. Due to the increased use of automated immunoassay analyzers, chemiluminescence has become one of the most common immunoassay detection methods used in the clinical laboratory setting. Chemiluminescence (also called bioluminescence when it occurs in fireflies and some dinoflagellates, coelente-rates, and fungi) is fluorescence. However, what is... 

The ELISA and EIA receptor systems measure substances at concentrations as low as a few nanograms (10 g). This sensitivity is not sufficient for detecting many substances and alternate methods have been devised. One is chemiluminescence immunoassay (CLIA), which can measure concentrations in femtogram (10 g) quantities. CLIA depends on the detection of emitted light associated with the dissipation of energy from a substance... 

Similar to the immunoassay techniques, radioimmunoassay, enzyme immunoassay, and chemiluminescence immunoassay are also applied and have proved useful. All techniques used for immunoassay represent coupling between the specificity of the antibody-antigen reaction and the sensitivity of the radiometric, electrometric, and chemiluminescence techniques. The limit of detection for immunoassay depends on the antibody affinity.128 130 Materials such as silica,131132 latex,133134 and alkylamine films135 are used for antibody absorption. SEM,136 scanning tunneling microscopy,137 and scanning force microscopy138 have been employed as tools for visualization of the immobilized antibodies. 

Metzger, J., M. Blobner, and P. B. Luppa. 2001. Sensitive chemiluminescence immunoassay for the determination of rat serum al-acid glycoprotein. Clinical Chemistry and Laboratory Medicine 39 514—518. 

Bidlingmaier, M., Suhr, J., Ernst, A., et al. (2009) High-sensitivity chemiluminescence immunoassays for detection of growth hormone doping in sports. Clinical Chemistry, 55 445-453. 

The high specifity of antigen-antibody reactions, and the sensitivity of these reactions, combined with the equally high sensitivity of chemi- and bioluminescence reactions, have led to the development of methods of chemiluminescent immunoassays, as an alternative to the commonly used radioimmunoassay [119]. 

Ru(bpy)32+ itself can be determined with great sensitivity in an excess of an amine to subpicomolar levels [39], This has led to the development of electro-chemiluminescent labels based on Ru(bpy)32+ derivatives that have found successful applications in ECL immunoassay and DNA probe analysis. These are discussed in Sec. 9. 

To test our new signal reagent based on GZ-11 the detection system was applied to two competitive-format immunoassays. These two assays (for atrazine and clenbuterol) normally use chromogenic detection systems. While these colorimetric assays may be adequate for laboratory use, chemiluminescent detection offers potential advantages in sensitivity and on site screening applications [33],... 

HRP substrates (Sred) can be selected to give products that can be monitored easily by colorimetric, fiuorometric or chemiluminescent methods. A popular choice in colorimetric assays is 3,3, 5,5 -tetrameth-ylbenzidine (TMB), a colorless substance that gives a blue product (Sox) on oxidation. Important considerations when choosing suitable substrates are cost, safety, sensitivity, solubility, and stability. It is sometimes necessary to use a substrate that gives an insoluble colored product, for example, in histochemical staining or membrane-bound immunoassays. 

Dioxetanes, labeled with triggers sensitive to the alkaline-phosphatase enzyme, serve as highly sensitive chemiluminescent probes in numerous bioassays. Current applications include immunoassays, membrane-based detection of proteins and nucleic acids, and microplate-based and array-based nucleic-acid detection. ... 

Since high-affimty recombinant antibodies are becoming easier to produce, it is important to be able to measure affinities with rigorous and reliable, yet user-friendly methods. Competition immunoassays (45,46) meet these criteria, but radioactive antibody labeling or use of fluorogenic or chemiluminescent substrates is needed for affinities >109 owing to the limits of sensitivity in... 

The LIA is an immunoassay in which the antigen or antibody are labeled with either a chemiluminescent or bioluminescent tags (41, 58). Luminescent molecules are produced by oxidation reactions. Bis-phenyl oxalates in presence of hydrogen peroxides are used for chemiluminescent assays and luciferin in presence of luciferase enzyme is used for bioluminescent assays. The sensitivity of the LIA s are in the pg/ml or lower range. 

Zhao, L., J.-M. Lin, Z. Li, et al. 2006. Development of a highly sensitive, second antibody format chemiluminescence enzyme immunoassay for the determination of 17[beta]-estradiol in wastewater. Anal. Chim. Acta 558 290-295. 

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