Radiometric Detection Technologies
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Authored by: Paul Taylor, Boehringer Ingleheim Inc.
Filter Binding Assays
Scintillation Proximity Assays (SPA)
Scintillation Proximity Assays (SPA) use scintillant-containing beads (polyvinyltoluene, PVT and yttrium silicate, YSi) which emit light in the 350-500 nm range when in close proximity to low energy, short range electron emitting radioisotopes such as 3H and 125I. Electrons emitted from labeled molecules that are not close to the surface dissipate their energy and are not detected. The assay format is semi-homogenous (the beads typically sink over time) and avoids the cumbersome filtration and washing procedures associated with filter binding assays. Typically an antibody, receptor molecule or streptavidin is used to coat the beads as a capturing mechanism for measuring incorporated radiolabel.
FlashPlates® contain scintillant embedded in polystyrene wells and these produce light directly when proximal to a captured radioisotope on the well surface.
LEADseeker™ detection is mechanistically similar to SPA but uses beads which use europium as a scintillant and emit light at 615 nm.
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