Superparamagnetic Nanostructures for Split-Type and Competitive-Mode Photoelectrochemical Aptasensing

Photoelectrochemical sensing has developed rapidly in the past decade because of its inherent advantages of economic devices and low background noise. However, traditional assembly of photoelectric beacons, probes, and targets on the ITO electrode solid–liquid interface inevitably leads to time-consuming, limited selectivity, poor stability, and nonreproducibility. To overcome these drawbacks, in this work, a unique split-type PEC aptasensor for carcinoembryonic antigen (CEA) was developed in virtue of the sandwich-like structure comprised of magnetic-optical Fe3O4@SiO2@CdS-DNA1, CEA aptamer, and signal element SiO2–Au-DNA2. The sandwich-like structure is easily formed in the liquid phase and can be triggered by competition from low-abundance CEA, resulting in dissociation. By further photocurrent measurement in pure phosphate buffer saline (PBS), coexisting species can be effectively removed from the modified electrode, improving selectivity, stability, and repeatability. These advantages benefit from the preparation of uniform and monodispersed Fe3O4@SiO2@CdS and SiO2–Au particles, DNAs assembly, and an elegant design. Additionally, the as-designed signal-on PEC aptasensor is highly sensitive, short time-consuming, and economical, enabling the detection of CEA in serum specimens. It not only provides an alternative to CEA immunosensors, but also paves the way for high-performance PEC aptasensors.