Smartphone-controlled portable photoelectrochemical immunosensor for point-of-care testing of carcinoembryonic antigen

Carcinoembryonic antigen (CEA) is expressed in many tumor cells and is an important cancer marker in human serum. To assess human health, a rapid and accurate real-time detection method should be established for the sensitive detection of CEA. In this work, real-time and on-site CEA detection was achieved by constructing sandwich-type photoelectrochemical (PEC) immunosensor and using a portable electrochemical workstation controlled by a smartphone. The employment of Zn-doped Fe2O3/CdIn2S4 (Zn-Fe2O3/CdIn2S4) is proposed for the first time as a sensing platform for PEC sensor. Due to its suitable band gap combination, a stepped electron transfer pattern provides a stable photocurrent response. Ag@CuWO4 as an antibody marker can amplify the sensor signal due to its ability to form a Z-type electron transfer mode with CdIn2S4. The Box-Behnken experiment was used to eliminate the interaction of experimental conditions and screen out the optimal experimental conditions for the immunosensor. In addition, the PEC immunosensor has a good linear relationship with CEA in the detection range of 100 fg/mL to 100 ng/mL, with a detection limit as low as 14.7 fg/mL (S/N = 3). The immunosensor has portable characteristics, good stability, reproducibility, specificity, and storage stability. It showed appreciable recoveries and low relative standard deviations in human serum sample analysis. This PEC assay paves a new point-of-care testing method for other cancer markers, particularly environmental contaminants.