CeO₂/g-C₃N₄ photoactive nanozyme-based colorimetric immunoassay for carcinoembryonic antigen detection

Enzyme-mimicking nanomaterials have gained significant attention for use in colorimetric immunoassays. However, further enhancing their mimetic enzyme activity remains crucial for improving assay sensitivity. In this study, CeO₂/g-C₃N₄ nanozymes were synthesized with enhanced catalytic activity when exposed to visible light. The irradiation facilitates electron transfer within the CeO₂/g-C₃N₄ nanomaterials, leading to the generation of reactive oxygen species (ROS). These ROS then promote the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB), causing a distinct color change. Based on this, a novel colorimetric immunoassay platform was developed, using the CeO₂/g-C₃N₄ nanomaterials as labels. Under visible light, the color development signal was significant amplified, resulting in improved sensitivity. This approach showed a linear response for the detection of carcinoembryonic antigen (CEA) in the range 0.5-30 ng/mL, with a limit of detection (LOD) of 0.13 ng/mL. The assay also demonstrated high specificity and excellent reproducibility. Consequently, this method offers a promising strategy for early cancer diagnosis and holds considerable potential for wider clinical applications.