ABSTRACT
We have previously shown that a gold-conjugated secondary label can be used to reduce the limit of detection in a diffraction-based assay by more than 40-fold. We now show that by using a combination of a peroxidase-conjugated secondary label and a precipitating substrate the limit of detection in a diffraction-based assay can be reduced by more than 1000-fold. The response to secondary enhancement was linear for concentrations from 50 to 2000 pg/mL of antidigoxin.
Subject(s)
Immunoenzyme Techniques/methods , Peroxidase/metabolism , Animals , Cattle , Digoxin/analysis , Digoxin/immunology , Digoxin/metabolism , Immunoenzyme Techniques/instrumentation , Lasers , Scattering, Radiation , Sensitivity and Specificity , Serum Albumin, Bovine/metabolismABSTRACT
It is shown that diffraction-based sensing can be enhanced for diagnostic purposes through the use of a secondary label. The limit of detection for anti-rabbit IgG was reduced more than 40-fold by using a gold-conjugated secondary antibody. The response to secondary antibody binding was linear for concentrations from 25 to 500 ng/ml of anti-rabbit IgG, suggesting that quantitative determinations can be readily done. Moreover, the binding of the secondary antibody was observed as soon as 1 min after its introduction to the surface-bound primary complex.
