Target dual-recycling-induced bipedal DNA walker and Bi2WO6/Bi2S3 cascade amplification strategy in photoelectrochemical biosensor for TP53 detection

A novel photoelectrochemical (PEC) biosensor was proposed for the ultrasensitive detection of nucleic acids, which coupled with an amplification strategy the bipedal DNA walker triggered dual recycle and Bismuth tungstate/Bismuth sulfide composite material (Bi2WO6/Bi2S3) as an excellent photoelectric layer on the surface of electrode. Ag2S quantum dots (QDs) as tags conjugated with DNA strand 2 (S2) were introduced on the electrode to increase the photocurrent response. With the participation of exonuclease III (Exo Ⅲ), the triple helix conformation of DNA hairpin 1, 2 (H1, H2) and target was disassembled, and the double bipedal DNA walkers were created to participate in next recycle. Catalyzed by Exo Ⅲ, the photocurrent signal dropped as the Ag2S QDs were forced away from the electrode surface. Based on the bipedal DNA walker triggered dual recycle cascade amplification strategy, the proposed PEC biosensor was used to detect target DNA TP53. Under optimized conditions, the photocurrent responded to target concentration variation from 10 fM to 1 μM with a detection limit of 5.83 fM. This work provides an effective method for the detection of nucleic acids biomarkers.