A simple and fast chromogenic reaction based on Ag₃PO₄/Ag nanocomposite for tumor marker detection

Colorimetric assay is a powerful tool for detection of tumor markers with the outstanding advantages of visualization and simple analytical instruments. Herein, a simple and fast chromogenic reaction was developed based on Ag₃PO₄/Ag nanocomposite synthesized by one-step chemical bath method. And the Ag₃PO₄/Ag nanocomposite owned the ability of oxidizing of TMB under the acidic condition due to the hydrolytic action. The nanocomposite was characterized by transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Then, the colorimetric immunoassay was constructed by utilizing Ag₃PO₄/Ag nanocomposite as molecular labels for carcino embryonie antigen (CEA, UniProt accession number: P06731) detection. The blue color with gradient change was observed with the increasing of CEA concentrations. Under optimal conditions, the variation between absorbance values and CEA levels was linear in the range of 0.2ngmL^-1 ~ 2.5ngmL^-1 with the detection limit of 0.03ngmL^-1. More importantly, the developed colorimetric immunoassay exhibited good selectivity, repeatability, stability and potential application in the real serum sample detection.