Sol particle immunoassays using colloidal gold and neutron activation

The feasibility of performing immunoassays with colloidal gold labels and detection of 198Au 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 252Cf 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 252 Cf source is limited to about 10-15 mol. The practical limitations of the assay's sensitivity at this point are due to background signals from reagents and/or nonspecific binding of the gold labeled reagent. (author) 13 refs.; 2 figs.; 1 tab