Photoelectrochemical platform for MicroRNA let-7a detection based on graphdiyne loaded with AuNPs modified electrode coupled with alkaline phosphatase.

In this work, a photoactive material, Graphdiyne (GDY) loaded with AuNPs (AuNPs-GDY), was successfully synthesized. The fabricated material made use of the natural band-gap structure of GDY, which could produce hole-electron pairs and the plasmon resonance effect of AuNPs to obtain a high photoelectrochemical (PEC) response. AuNPs-GDY PEC response changed with the mass ratio of GDY to tetrachloroauric acid. When the mass ratio of GDY to tetrachloroauric acid was 1:2.5, AuNPs-GDY exhibited the best PEC performance. Thus, the best one was selected as the photoactive material to establish a PEC biosensor for microRNA detection. The PEC biosensor used the alkaline phosphatases as catalyzer to generate ascorbic acid in situ, which provided a low background signal and a high PEC response. The cancer marker, MicroRNA let-7a, was chosen as a target model. Under optimal condition, potential 300 mV and pH 8.0, the PEC biosensor had a detection limit of 3.3 × 10-19 M and a good linearity with microRNA let-7a concentration ranged from 1.0 × 10-18 M to 1.0 × 10-10 M. This PEC biosensor opened a promising platform using GDY to fabricate analytical method and detect microRNA at ultralow levels for diagnoses.