Photoelectrochemical biosensing platform based on switch of photocurrent polarity of CdS/Ni-CAT nanorod arrays by Au@Cu2O for highly selective and sensitive CEA detection.

Sensitive and accurate determination of tumour biomarkers is extremely important for early cancer diagnosis. Herein, a photoelectrochemical biosensor platform was constructed for ultrasensitive tumour biomarker detection by utilizing Au@Cu2O to switch the photocurrent polarity of CdS/Ni-catecholates metal-organic framework (Ni-CAT) nanorod arrays grown in situ on ITO. The Ni-CAT obtains close contact with ITO and forms a Z-scheme heterojunction with CdS, which improves the photogenerated electron transfer ability. When the target CEA (a model tumour biomarker) was present, CdS/Ni-CAT conjugated with aptamer 1 and Au@Cu2O conjugated with aptamer 2 to form a sandwich-type complex with the CEA, resulting in the switch of photocurrent polarity of CdS/Ni-CAT from anode to cathode. Owing to the high photogenerated carrier separation efficiency of Au@Cu2O core-shell heterojunction, the constructed biosensor exhibited ultrasensitive for the detection of CEA with a wide linear range of 0.1 pg·mL-1-10 ng mL-1 and effectively eliminated false-positive or false-negative signals, which provides a potential alternative solution for the determination of tumour markers in bioanalysis and clinical diagnosis.