Double layer enzyme modified carbon nanotubes as label for sandwich-type immunoassay of tumor markers.

n immunosensor was prepared for the determination of carcinoembryonic antigen (CEA). It is based on the use of multiwalled carbon nanotubes (MWCNTs) along with horseradish peroxidase-labeled antibody. The enzyme was assembled onto MWCNTs templates using the layer-by-layer technique and then conjugated to carcinoembryonic secondary antibodies (Ab) as the enzyme label. The resulting assembly results in a largely amplified sensitivity. The response is linear in the range of 0.05 to 45 ng mL, with a detection limit of 16.0 pg mL. The immunosensor possesses good stability and good reproducibility. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]