Photoelectrochemical (PEC) immunoassays exhibiting high sensitivity and decent operability have considerable potential in areas such as cancer diagnostics. In particular, cathodic PEC configurations can prevent interference from reductive substances, which can occur in biological samples; however, challenges remain in terms of sensitivity and operability. In this study, separate-type PEC immunoassays were developed for carcinoembryonic antigen (CEA) by combining microplate-based immune recognition and off–on cathodic PEC detection. Polydopamine (PDA)-coated Prussian blue (PB) nanoparticles (PB@PDA NPs) were used as signal tags to label the detection antibody. The PB NPs and PDA captured on the microplates both disassembled under strongly alkaline conditions to generate redox-active electron acceptors. The disassembled products were quantitatively transferred to PEC detection cells and synergistically enhanced the PEC current with microstructured BiOI, which operated as a cathodic semiconductor electrode. As proof of principle, carcinoembryonic antigen (CEA) was applied to elucidate the potential application of PEC immunoassay in clinical diagnosis, and the obtained linear range of the sensor was 0.001–100 ng mL⁻¹ with the detection limit of 54.9 fg mL⁻¹ (S/N = 3). The proposed separate-type off–on PEC strategy showed high sensitivity and decent operability for CEA detection, indicating its potential for the identification of other tumor markers.

具有高灵敏度和良好可操作性的光电化学 (PEC) 免疫测定在癌症诊断等领域具有相当大的潜力。特别是，阴极 PEC 配置可以防止生物样品中可能出现的还原物质的干扰；然而，在敏感性和可操作性方面仍然存在挑战。在这项研究中，通过结合基于微孔板的免疫识别和关-开阴极 PEC 检测，开发了用于癌胚抗原 (CEA) 的分离型 PEC 免疫测定。聚多巴胺 (PDA) 包被的普鲁士蓝 (PB) 纳米粒子 (PB@PDA NPs) 被用作标记检测抗体的信号标签。微孔板上捕获的 PB NPs 和 PDA 均在强碱性条件下分解，产生氧化还原活性电子受体。将分解后的产物定量转移到 PEC 检测池中，并与用作阴极半导体电极的微结构 BiOI 协同增强 PEC 电流。作为原理证明，应用癌胚抗原 (CEA) 阐明 PEC 免疫测定在临床诊断中的潜在应用，获得的传感器线性范围为 0.001–100 ng·mL⁻¹，检测限为 54.9 fg mL ⁻¹  (S/N = 3)。所提出的分离式 off-on PEC 策略对 CEA 检测显示出高灵敏度和良好的可操作性，表明其具有识别其他肿瘤标志物的潜力。