The bio-barcode amplification assay. The assay uses magnetic particles functionalized with monoclonal antibodies that recognize and bind ADDLs. The ADDLs are then sandwiched with a nanoparticle probe, modified with double-stranded DNA and an anti-ADDL polyclonal antibody. After repeated washing while using a magnet to immobilize the magnetic particles, a dehybridization step releases hundreds of barcode DNA strands for each antigen-binding event (From . Copyright (2005) National Academy of Sciences, USA).