Split-type photoelectrochemical immunoassay for sensitive quantification of carcinoembryonic antigen based on target-induced formation of Z-type heterojunction.

Carcinoembryonic antigen (CEA), a vital biomarker, plays a significant role in the early diagnosis and prognostic estimation of malignant tumors. In this study, a split-type photoelectrochemical immunoassay for the sensitive quantification of CEA has been successfully developed based on the target-induced formation of a Z-type heterojunction. First, gold nanoparticle-decorated ZnInS (AuNPs/ZnInS) composites were synthesized and used for the fabrication of photoelectrodes. Then, the detection antibody labeled with Ag nanoparticles was formed and applied for the biorecognition of CEA and subsequent liberation of Ag ions to induce the formation of AgS/AuNPs/ZnInS, a Z-type heterojunction, on the photoelectrode. The Z-type AgS/AuNPs/ZnInS heterojunction with effectively promoted separation of photogenerated charge carriers could lead to a markedly enhanced photocurrent response and highly sensitive quantification of CEA. Moreover, the three-dimensional spatial structure of ZnInS provides abundant active sites for the reaction and exhibits non-enzymatic properties, which are conducive to the further improvement of the analytical performance of CEA. The developed split-type photoelectrochemical immunoassay with good sensitivity, satisfactory selectivity, reliable stability, wide dynamic linear range (0.01-20 ng mL), and low detection limit (7.3 pg mL) offers valuable insights into the development of novel PEC biosensing models for the detection of tumor biomarkers and holds potential application value in the field of disease diagnosis.