ZnO quantum dot labeled immunosensor for carbohydrate antigen 19-9

Using ZnO quantum dots as electrochemical and fluorescent labels, a sandwich-type sensitive immunoassay was developed to detect carbohydrate antigen 19-9 (CA 19-9) which is a preferred label for pancreatic cancer. The immobilization process was mainly carried out through the electrostatic adsorption based on the high isoelectric point of ZnO, and the sandwich structure was built through the immunoreaction of CA 19-9 antibodies and antigens. The immunological recognition of CA 19-9 was converted into detection of the amplified signals of the square wave stripping voltammetry (SWV) and intrinsic photoluminescence of the labeled quantum dots. The electrochemical assay demonstrated a dynamic range of 0.1-180 U/ml with detection limit of 0.04 U/ml, while the optical spectral detection revealed 1-180 U/ml with detection limit of 0.25 U/ml.