Ultrasensitive photoelectrochemical immunosensor based on floral cluster SnS2/ZnCdS heterostructure for the detection of CA199

The early and accurate detection of tumor markers is crucial for cancer diagnosis, prognosis, and treatment monitoring. Carbohydrate antigen 199 (CA199), as a key biomarker of pancreatic, gastric, and colorectal cancers, is widely used in the clinical management. The development of sensitive, rapid and cost-effective detection methods for CA199 is of paramount importance in improving early detection rates and patient outcomes. In this study, we present a novel photoelectrochemical (PEC) immunosensor based on a SnS₂/ZnCdS heterostructure designed for the ultrasensitive detection of CA199. The unique heterojunction between SnS₂ and ZnCdS enhances photocurrent generation by effectively suppressing charge recombination and improving charge separation. Furthermore, the flower-like morphology of the heterostructure further boosts light absorption and photogenerated carrier transport, resulting in significantly enhanced sensor performance. This label-free PEC immunosensor exhibits outstanding stability, reproducibility and selectivity, with a broad detection range from 0.01 to 1000 U/mL and an ultra-low detection limit of 1.00 × 10^-3 U/mL. These features demonstrate the potential of this sensor as a powerful tool for sensitive CA199 detection, offering promising applications in cancer diagnostics and monitoring.