Spatial-resolved and self-calibrated 3D-printed photoelectrochemical biosensor engineered by multifunctional CeO/CdS heterostructure for immunoassay.

A spatial-resolved and self-calibrated photoelectrochemical (PEC) biosensor has been fabricated by a multifunctional CeO/CdS heterostructure, achieving portable and sensitive detection of carcinoembryonic antigen (CEA) using a homemade 3D printing device. The CeO/CdS heterostructure with matched band structure is prepared to construct the dual-photoelectrodes to improve the PEC response of CeO. In particular, as the photoactive nanomaterial, the CeO also plays the role of peroxidase mimetic nanozymes. Therefore, the catalytic performance of CeO with different morphologies (e.g., nano-cubes, nano-rods and nano-octahedra) have been studied, and CeO nano-cubes (c-CeO) 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, HO can be produced from the catalytic oxidization of glucose substrate by GOx, which is further catalyzed by CeO 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 provides a promising way for ultrasensitive immunoassay in clinic application in complex environments.