No abstract

We report a visualization assay for carcinoembryonic antigen (CEA). The assay was prepared based on target‐specific recognition, aptamer‐based DNAzyme self‐catalysis, and colorimetric reaction. Aptamer of CEA was gathered at the surface of magnetic beads for sandwiched co‐conjugate when CEA was added. The second aptamer (Apt2) on the beads was folded into G‐quadruplex by KCl to make G‐quadruplex‐hemin DNAzyme with hemin. Apt2‐based DNAzyme catalyzed H2O2‐mediated oxidation of 3,3′,5,5′‐tetramethylbenzidine, resulting in color changes and significant increase in absorption intensity at 450 nm (ΔA450nm). Yellow products can be observed with naked eyes when over 1.0 ng/mL CEA was added and there was a linear correlation between ΔA450 nm and CEA concentrations in the range of 0.1–8.0 ng/mL with the detection limit of 0.06 ng/mL. The proposed method was then used to determine CEA in human serum from healthy people and tumor patients, revealing a correlation with data from the electrochemiluminescent immunoassay. Owing to its simplicity, selectivity, and low‐cost, this method is a promising candidate for detecting CEA and clinical diagnosis of cancer.