PSA antibody-pair was used for the PSA detection (ab256313). The detector antibody was labeled using an Alexa Flour 647 labeling kit (A-20186). 100μL of the detector antibody is added to the given Alexa and incubated for 2 hours at room temperature with a gentle invention of the vial every 15 minutes to fully dissolve the dye. The purification steps involve the removal of unbounded Alexa's to the antibody.