Isotope-labeled immunoassays without radiation waste

Area of Science:

• Biochemistry
• Analytical Chemistry
• Immunology

Background:

• Immunoassays traditionally use radioisotope labels, posing challenges like radiation hazards, regulatory hurdles, and short reagent shelf-life.
• Nonisotopic labels are common, but isotopic labeling offers superior analyte incorporation without structural alteration.

Purpose of the Study:

• To develop a novel immunoassay format utilizing a long-life isotope label (carbon-14) and accelerator mass spectrometry (AMS) for detection.
• To overcome the limitations of traditional radioimmunoassays (RIA) while retaining their sensitivity advantages.

Main Methods:

• Development of an immunoassay format employing carbon-14 ((14)C) as the label.
• Utilizing accelerator mass spectrometry (AMS) for highly sensitive quantification of (14)C-labeled analytes.
• Assay validation using atrazine and 2,3,7,8-tetrachlorodibenzo-p-dioxin.

Main Results:

• Achieved attomole-level quantification sensitivity for (14)C, with assay sensitivity limited by antibody affinity (K(d)) rather than detection.
• Detection limits for atrazine and dioxin were 2.0 x 10(-10) M and 2.0 x 10(-11) M, respectively, surpassing standard enzyme immunoassays.
• Used minimal amounts of (14)C (<1 dpm per assay), facilitating disposal as nonradioactive waste.

Conclusions:

• The developed (14)C-AMS immunoassay provides the sensitivity of RIA without the associated radioactive waste disposal problems.
• This method offers a viable alternative for sensitive bioanalysis, overcoming practical limitations of traditional radioisotope-based assays.