Ultrasensitive Photocathodic Biosensor Based on the CuO/PTB7-Th/PDA Composite with Enhanced Photoelectrochemical Performance for the Detection of MicroRNA-375-3p.

Herein, an ultrasensitive photocathodic biosensor was fabricated based on CuO/PTB7-Th/PDA photoactive materials with high photocarrier separation efficiency for the detection of microRNA-375-3p. Impressively, the photocathodic signal of the CuO material was significantly enhanced by using PTB7-Th as an energy level-matching photoactive material to enhance the bulk charge separation and ,-bis (2-(trimethylammoniumiodide) propylene) perylene-3,4,9,10-tetracarboxydiimide (PDA) as an interfacial charge transfer mediator to efficiently suppress charge recombination at the photoelectrode/electrolyte interface. Compared with the pristine CuO as a photocathode, the obtained CuO/PTB7-Th/PDA exhibited a 17 times higher photocathodic signal. As a proof of concept, a PEC biosensor was fabricated by using CuO/PTB7-Th/PDA as a photoactive material and a target-triggered 3D DNA walker integrated with the dumbbell hybridization chain reaction (DHCR) as a signal amplifier to achieve the sensitive detection of microRNA-375-3p with a detection limit of 0.3 fM. This work provided a method to increase the photocurrent signal and the sensitivity of PEC-sensing platforms for the detection of biomarkers and disease diagnosis.