SOL PARTICLE IMMUNOASSAYS USING COLLOIDAL GOLD AND NEUTRON-ACTIVATION

The feasibility of performing immunoassays with colloidal gold labels and detection of Au-198 by neutron activation has been demonstrated with measurements of human immunoglobulin and of serum antibodies to human immunodeficiency virus type 1. The detection sensitivity achieved after activation in a high flux reactor or with a water moderated Cf-252 source, by gamma-counting or by autoradiography. is similar to the sensitivity obtained with absorbance measurements in the more common enzyme immunoassays. The reactor based neutron activation assay allows detection of 10(-16) mol of analyte in routine operation with possible extension to 10(-20) mol. The sensitivity with the 1.3 Ci Cf-252 source is limited to about 10(-15) mol. The practical limitations of the assay's sensitivity al this point are due to background signals from reagents and/or nonspecific binding of the gold labeled reagent.