Development of a homogeneous phosphorescent immunoassay for the detection of polychlorinated dibenzo-p-dioxins

A homogeneous immunoassay for dioxins was developed using a phosphorescent label for detection. A dioxin derivative was conjugated to Pt-coproporphyrin. In the assay, when the antibodies against dioxin (DD3) were bound to the phosphorescent conjugate, the signal from Pt-coproporphyrin was quenched. The interaction between antibody and the conjugate was studied by time-resolved luminescence spectroscopy. As concentrations of dioxin standards increased from 39 pg/well to 2.5 ng/well the lifetime of the phosphorescence of the shortlived component increased from 25.6 microseconds to 58.9 microseconds. This increase in half-life was associated with a dose dependent quenching of the phosphorescence. The inhibition obtained is similar to that for a reported enzyme-based immunoassay, but the data were obtained in minutes instead of hours.