Highly photosensitive colorimetric immunoassay for tumor marker detection based on Cu²⁺ doped Ag-AgI nanocomposite

Visual detection of tumor markers with accuracy and selectivity exhibits significant advantages for cancer early diagnosis due to its low-cost and simple analytical instruments. Herein, a highly photosensitive colorimetric immunoassay for carcino embryonie antigen (CEA, as a model) detection based on Cu²⁺ doped Ag-AgI nanocomposite was constructed. First, Cu²⁺ doped Ag-AgI nanocomposite (Cu²⁺/Ag-AgI) owned the ability of oxidization of TMB was synthesized by impregnation method, which was characterized by transmission electron microscope (TEM), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray powder diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS). Second, based on sandwich-type immunoassay, the immunocomplex was built on the surface of magnetic bead by utilizing Cu²⁺/Ag-AgI as labels. The blue color of TMB_ox was obtained under visible irradiation and ultraviolet spectrum scanning was carried out in ABS buffer solution. Under optimal conditions, the absorbance values increased with the increasing of CEA concentrations in sample with the linearity range of 1.0pgmL^-1-5.0ngmL^-1. The detection limit was 0.13pgmL^-1. More importantly, the developed colorimetric immunoassay exhibited good selectivity, repeatability, stability and possible applications in the real serum sample analysis.