Spatial-resolved and self-calibrated 3D-printed photoelectrochemical biosensor engineered by multifunctional CeO₂/CdS...

A spatial-resolved and self-calibrated photoelectrochemical (PEC) biosensor has been fabricated by a multifunctional CeO₂/CdS heterostructure, achieving portable and sensitive detection of carcinoembryonic antigen (CEA) using a homemade 3D printing device. The CeO₂/CdS heterostructure with matched band structure is prepared to construct the dual-photoelectrodes to improve the PEC response of CeO₂. In particular, as the photoactive nanomaterial, the CeO₂ also plays the role of peroxidase mimetic nanozymes. Therefore, the catalytic performance of CeO₂ with different morphologies (e.g., nano-cubes, nano-rods and nano-octahedra) have been studied, and CeO₂ nano-cubes (c-CeO₂) achieve the optimal catalytic activity. Upon introducing CEA, the sandwich-type immunocomplex is formed in the microplate using GOx-AuNPs-labeled second antibody as detection antibody. As a result, H₂O₂ can be produced from the catalytic oxidization of glucose substrate by GOx, which is further catalyzed by CeO₂ to form •OH, thus in situ etching CdS and decreasing the photocurrents. The self-calibration is achieved by the dual-channel photoelectrodes on the homemade 3D printing device to obtain the photocurrents ratio, thus effectively normalizing the fluctuations of external factors to enhance the accuracy. This integrated biosensor with a detection limit as low as 0.057 ng mL^-1 provides a promising way for ultrasensitive immunoassay in clinic application in complex environments.