Ultrasensitive Photocathodic Biosensor Based on the Cu 2 O/PTB7-Th/PDA + Composite with Enhanced Photoelectrochemical Performance for the Detection of MicroRNA-375-3p.

Herein, an ultrasensitive photocathodic biosensor was fabricated based on Cu 2 O/PTB7-Th/PDA + photoactive materials with high photocarrier separation efficiency for the detection of microRNA-375-3p. Impressively, the photocathodic signal of the Cu 2 O material was significantly enhanced by using PTB7-Th as an energy level-matching photoactive material to enhance the bulk charge separation and N , N -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 Cu 2 O as a photocathode, the obtained Cu 2 O/PTB7-Th/PDA + exhibited a 17 times higher photocathodic signal. As a proof of concept, a PEC biosensor was fabricated by using Cu 2 O/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.