TRF Performance of Thermo Scientific Appliskan® with Europium Sensitivity Assay
MIB Application Laboratory, Thermo Fisher Scientific, Vantaa, Finland
Introduction
Time-resolved fluorescence (TRF) is a special form of fluorescence with a delay time between the excitation of the sample and the emission detection. The labels used in TRF are fluorescent lanthanide chelates, rare earth metals (Eu, Tb, Sm, Dy) with a specific ligand molecule. Lanthanide chelates have a very long fluorescent lifetime compared to traditional fluorescent labels, which makes them excellent labels for TRF. The fluorescence of the traditional fluorescent labels decays in nanoseconds, whereas the fluorescence of the lanthanide chelates can last for hundreds of microseconds. Lanthanide chelates also have a very large Stoke’s shift (the difference between excitation and emission wavelengths) and their emission peak is always very sharp, which makes them good labels for multianalyte assays.
The delay time in TRF measurements reduces the effect of background interference. The background fluorescence originates from plate materials, reagent components, biological samples etc., and most of it decays very rapidly during the TRF delay time. Therefore TRF is a way to separate the fluorescence of the label from the background fluorescence. When the background fluorescence is reduced, the sensitivity of the assay is increased.
The TRF performance of Thermo Scientific Appliskan® was determined by the europium (Eu) sensitivity assay. Europium is the lanthanide ion used chiefly in TRF measurements.