Enzyme-amplified split-type photoelectrochemical immunoassay for quantitative monitoring of carbohydrate antigen 19–9 (CA19–9) based on Au-ZnIn2S4 heterojunction

The development of rapid and sensitive CA19–9 (carbohydrate antigen 19–9) analytical methods for early screening of potential patients, especially in clinical situations, is important for controlling the progression of pancreatic cancer. Herein, a new photoelectrochemical (PEC) immunoassay has been devised for the ultrasensitive detection of CA19–9 using gold nanoparticle-modified ultrathin ZnIn 2 S 4 nanosheets (Au-UZNS) as the photoactive substrate. Notably, the alkaline phosphatase (ALP) labeled on the detection antibody (ALP-dAb) serves as the signal amplifier that catalyzes the production of large amounts of ascorbic acid (AA) after the sandwiched immunoreaction. The generated AA is an outstanding electron donor, thereby improving the intensity of the photoactive substrate. Under the optimized parameters, the Au-UZNS-based PEC immunosensor displays an excellent response to CA19–9 ranging from 0.01 to 500 U mL −1 with a limit of detection (LOD) of 4.7 mU mL −1 . Generally, the CA19–9 levels in the serum of high-risk pancreatic cancer patients range from 120 to 400 U mL −1 , while the levels in normal humans range from 0 to 40 U mL −1 . Therefore, the exceptionally low LOD value of the proposed method is sufficient to meet the threshold for clinical detection and holds significant potential for further application.