Ultrasensitive CEA detection using SiO/AuNPs-mediated dual inhibition in a signal-off-type photoelectrochemical immunosensor.

An essential tumor marker for the diagnosis and therapy monitoring of numerous cancers is carcinoembryonic antigen (CEA). The current CEA detection method still has drawbacks, such as time-consuming, expensive, and complex analysis. Photoelectric chemical immunosensors show great potential in CEA detection because of their advantages of low cost, high sensitivity and easy operation. The aim of this study was to develop an ultra-sensitive photoelectrochemical (PEC) immunosensor based on InS/MnInS heterojunction for the detection of CEA. MnInS nanosheets were grown in situ on the surface of InS nanosheets by a simple hydrothermal method, and heterojunctions with matching lattice parameters were constructed. Its band structure optimizes its interaction with visible light, thereby improving its photoelectrochemical properties. Due to the specific recognition of antigens and antibodies, SiO/AuNPs-Ab2 was captured on the electrode surface, resulting in significant photoelectric signal quenching. Therefore, the PEC signal weakens with the increase of CEA concentration, and quantitative detection was realized. Under optimized experimental conditions, the linear detection range of the PEC immune sensor for CEA ranged from 0.5 pg/mL to 100 ng/mL, and the detection limit was as low as 0.143 pg/mL, showing extremely high sensitivity. The developed PEC immunosensor provides a promising technical means for the high sensitivity detection of CEA, and has the potential to be widely used in clinical diagnosis.