Efficient cathodic aptasensor coupling photoelectrochemical enhancement of PEDOT/Bi2S3/ZnO photoanode with signal amplification of Pt nanocatalysts

Detection of targets in real samples with high sensitivity and accuracy is very important and a challenge for the application of developed biosensors. Herein, a novel and efficient cathodic aptasensor coupling photoelectrochemical (PEC) enhancement of photoanodes with signal amplification of nanocatalysts was elaborated. The model target of carcinoembryonic antigen (CEA) was employed to demonstrate the performance. A three-dimensional (3D) PEDOT/Bi2S3/ZnO photoanode was fabricated via successive modification of bismuth sulfide (Bi2S3) nanosheets and a poly(3,4-ethylenedixythiophene) (PEDOT) layer on vertical zinc oxide (ZnO) nanorods. For the aptasensing cathode, after reduced graphene oxide (RGO) was deposited, the CEA aptamer was anchored on the cathodic substrate via the linking of chitosan. Part of the complementary DNA (cDNA) was labeled with Pt nanocatalyst to form the Pt-cDNA conjugate, which amplified the signal via DNA hybridization with the CEA aptamer. Target detection depended on a dramatic decrease in the current signal produced by both the escape of the signal amplifier and obvious steric hindrance of the captured CEA. Benefiting from the superior cosensitization structure of the photoanode and excellent catalytic ability for oxygen reduction of the labeled Pt nanocatalyst, the cathodic aptasensor demonstrated high sensitivity. Owing to the separation of the photoanode with biorecognition, the aptasensor also exhibited good selectivity in the biomatrix. This kind of cathodic aptasensor has offered an effective way to explore other high-performance biosensors for real applications.