Double ion-exchange reaction-based photoelectrochemical immunoassay for sensitive detection of prostate-specific antigen

This work developed a double ion-exchange reaction-based photoelectrochemical (PEC) immunoassay with the split-type detection mode for sensitive detection of prostate-specific antigen (PSA, used as a model). The nanocomposite of cadmium sulfide and nickel sulfide (CdS@NiS nanocomposite), as the photoactive material, was rapidly synthesized by two-step hydrothermal treatment. In the presence of target PSA, the cupric oxide nanoparticle (CuO NP) labeled detection antibody was introduced into the detection system by sandwich immunoreaction and the copper (Cu²⁺) ions was released from CuO nanoparticles by acid to participate in double ion-exchange reaction. The double ion-exchange reaction on the photoelectric sensing interface between Cu²⁺ and CdS@NiS nanocomposites formed the weak photoactive material Cu_xS (x = 1, 2) to reduce the photocurrent. Under optimal conditions, the double ion-exchange reaction-based PEC immunoassay exhibited good photocurrent responses toward target PSA within the dynamic working range from 0.01 ng mL⁻¹ to 50 ng mL⁻¹ at a low limit of detection (LOD) of 2.9 pg mL⁻¹. Besides, our work could achieve good reproducibility and high specificity under the split-type detection mode. Compared with human PSA ELISA kit, the accuracy obtained by our strategy was satisfactory. Importantly, this Cu²⁺-activated double ion-exchange reaction-based PEC immunoassay provides a promising platform for the detection of biomarkers.