LUMINESCENT OXYGEN CHANNELING ASSAY (LOCI(TM)) - SENSITIVE, BROADLY APPLICABLE HOMOGENEOUS IMMUNOASSAY METHOD

Luminescent oxygen channeling assay (LOCI(TM)) is a homogeneous immuno assay method capable of rapid, quantitative determination of a wide ra nge of analytes-including high and very loa concentrations of large an d small molecules, free (unbound) drug, DNA, and specific IgM. Assays have been carried out in serum and in lysed blood. Reliable detection of 1.25 mu U/L thyrotropin (TSH) and 5 ng/L hepatitis B surface antige n (HBsAg) corresponds to detection limits similar to 3- and similar to 20-fold lower, respectively than those of the best commercially avail able assays. An assay of chorionic gonadotropin is capable of quantifi cation over a 10(6)-fold range of concentrations without a biphasic re sponse. Latex particle pairs are formed in the assay through specific binding interactions by sequentially combining the sample and two reag ents. One particle contains a photosensitizer, the other a chemilumine scer. Irradiation causes photosensitized formation of singlet oxygen, which migrates to a bound particle and activates the chemiluminescer, thereby initiating a delayed luminescence emission. Assay times range from 1 to 25 min.