Bi2WO6-labeled antibody induced photocurrent polarity switching of ZnIn2S4-based photoelectrochemical immunosensor for the highly sensitive detection of carcinoembryonic antigen.

Developing effective detection methods for disease markers is essential for clinical diagnosis and therapeutic prognostic assessment. In this work, hollow Bi-doped Bi2WO6 was synthesized by using carbon sphere as template, and then it was used as the label of secondary antibody to induce current polarity reversal in the flower shaped ZnIn2S4 based photoelectrochemical (PEC) immunosensor. Thus the easily disturbed anodic photocurrent was converted to cathodic photocurrent with better resistance to interference from reducing substances. Furthermore, the reversal of polarity made the influence of background signal decrease, the detection range become wide, and the sensitivity increase. The introduced poly(dopamine) film could inhibit the anodic photocurrent of ZnIn2S4 in addition to fixing antibody, assisting Bi2WO6 in inducing subsequent current polarity conversion. Under the optimized conditions, the linear response range of the sandwich immunosensor was as wide as 0.0005-20.0 ng/mL, with a quite low limit of 0.18 pg/mL for the assay of model molecule carcinoembryonic antigen. The PEC sensor also exhibited satisfying selectivity and stability. It was applied to detect serum samples and satisfactory results were achieved.