Self-Circulation Oxygen-Hydrogen Peroxide-Oxygen System for Ultrasensitive Cathode Photoelectrochemical Bioassay Using a Stacked Sealed Paper Device.

In this work, a self-circulation oxygen-hydrogen peroxide-oxygen (O2-H2O2-O2) system with photogenerated electrons as fuel and highly active hemin monomers as operators was engineered for ultrasensitive cathode photoelectrochemical bioassay of microRNA-141 (miRNA-141) using a stacked sealed paper device. During the circulation, the photogenerated electrons from BiVO4/Cu2O photosensitive structures assembled on a reduced graphene oxide paper electrode first reduced the electron acceptors (dissolved O2) to H2O2, which was then catalytically decomposed by hemin monomers to generate O2 again. The regenerated O2 continued to be reduced, which made O2 and H2O2 stuck in the infinite loop of O2-H2O2-O2 accompanied by the fast consumption of photogenerated electrons, generating an amplified photocurrent signal. When a target existed, a duplex-specific nuclease-induced target recycling reaction with dual trigger DNA probes as the output was performed to initiate the assembly of bridge-like DNA nanostructures, which endowed the self-circulation system with dual destruction functions as follows. (i) Reduced fuel supply: the assembled DNA bridges acting as a negatively charged barrier prevented the photogenerated electrons from participating in the O2 reduction to H2O2. (ii) Incapacitation of operators: DNA bridging induced the dimerization of hemin monomers linked on the DNA hairpins to catalytically inactive hemin dimers, leading to the abortive regeneration of O2. These destruction functions resulted in the circulation interruption and a remarkably decreased photocurrent signal. Thus, the developed cathode photoelectrochemical biosensing platform achieved ultrasensitive miRNA-141 detection with a linear range of 0.25 fM to 1 nM and a detection limit of 83 aM, and it also exhibited high accuracy, selectivity, and practicability.