ELISAs (enzyme-linked immunosorbent assays) have commonly been used for quantitation of biomarkers and other analytes in a variety of sample types. While wash-based ELISAs provide excellent quantitation of the target biomolecule, there are several limitations to these assays including a narrow dynamic range and limited signal stability.
DELFIA® (Dissociation-Enhanced Lanthanide Fluorescent Immunoassay) time-resolved fluorescence technology (TRF) provides a wash-based assay based on a principle and workflow similar to ELISA, but with a wider dynamic range and a stable signal that can be measured from overnight to days, months or years post-assay with proper storage of plates.
In a DELFIA immunoassay, capture antibody is coated to a microplate. Sample is added, followed by a series of wash steps. Following the first series of washes, Europium-labeled detection antibody is added to each well. The plate is washed one final time, and Enhancement Solution is added. The Enhancement Solution releases the Europium from its chelate, allowing the formation of a new, highly fluorescent chelate in solution. Excitation at 320 or 340 nm leads to detectable emission at 615 nm. The amount of analyte is proportional to the emission signal which can be quantitated by interpolation from a standard curve. The time-resolved nature of the detection step minimizes background signal, resulting in a stable, maximized signal-to-background.
DELFIA offers benefits over traditional ELISA including:
- Wider dynamic range, up to 5 log
- Greater sensitivity
- Longer signal stability
- Miniaturizable
- Ability to multiplex