Integrating CuO/g-C3N4 p-n heterojunctioned photocathode with MoS2 QDs@Cu NWs multifunctional signal amplifier for ultrasensitive detection of AβO.

Superior to anodic photoelectrochemical (PEC) method, cathodic bioanalysis integrates merits of excellent anti-interference and high stability, representing a promising and competitive methodology in precise monitoring targets in complex matrices. However, serious consideration of photocathode is far behind the anodic one, developing high-performance photocathode for PEC biosensing is thus urgently desired. Herein, a high-performance cathodic PEC aptasensing platform for detection of amyloid-beta oligomers (AβO) was constructed by integrating CuO/g-C3N4 p-n heterojunction with MoS2 QDs@Cu NWs multifunction signal amplifier. The CuO/g-C3N4, exhibiting intense visible light-harvesting and high photoelectric conversion efficiency, was synthesized by in-situ pyrolysis of Cu-MOF and dicyandiamide. The MoS2 QDs@Cu NWs was obtained by electrostatical self-assembly, which acted not only as a sensitizer to boost PEC response, but also as a nanozyme for biocatalytic precipitation. The aptasensor was fabricated by DNA hybridization between the cDNA on photocathode and MoS2 QDs@Cu NWs-labeled aptamer. Based on "on-off-on" photocurrent response generated by multifunction signal amplification, ultrasensitive aptasensing of AβO was realized in a wider linear range from 10 fM to 0.5 μM with an ultralow detection limit of 5.79 fM. The feasibility of the sensor for AβO determination in human blood serum was demonstrated.