In this study, we examined the use of CdSe aqueous
quantum dots (AQDs) each conjugated to three
streptavidin as a fluorescent label to image
Tn antigen expression in various breast tissues via a sandwich staining procedure where the primary monoclonal anti-Tn antibody was bound to the
Tn antigen on the tissue, a
biotin-labeled secondary antibody was bound to the primary anti-Tn antibody, and finally the
streptavidin-conjugated AQDs were bound to the
biotin on the secondary antibody. We evaluated the AQD staining of
Tn antigen on tissue microarrays consisting of 395 cores from 115 cases including three
tumor cores and one normal-tissue core from each
breast cancer case and three
tumor cores from each benign case. The results indicated AQD-Tn staining was positive in more than 90% of the cells in the
cancer cores but not the cells in the normal-tissue cores and the benign
tumor cores. As a result, AQD-Tn staining exhibited 95% sensitivity and 90% specificity in differentiating
breast cancer against normal breast tissues and benign breast conditions. These results were better than the 90% sensitivity and 80% specificity exhibited by the corresponding horse radish
peroxidase (HRP) staining using the same
antibodies on the same tissues and those of previous studies that used different fluorescent labels to image
Tn antigen. In addition to sensitivity and specificity, the current AQD-Tn staining with a definitive threshold was quantitative.