Spatially separated Cu₂O/BiOI heterojunction and target-triggered DNA cascade amplification integrated highly...

In this work, a highly sensitive and accurate self-powered photoelectrochemical (SPEC) biosensor is successfully developed for ultrasensitive detection of adenosine triphosphate (ATP) through the rational integration of a dual-photoelectrode spatial separation strategy and a target-triggered nucleic acid cascade amplification. The spatially separated cuprous oxide (Cu₂O) photocathode and bismuth oxyiodide (BiOI) photoanode, combined with their well-matched energy band structures, not only facilitates efficient charge separation with extremely high initial photocurrent, but also eliminates the need for external power sources and mitigates the interference of foreign substances to improve the detection accuracy. Simultaneously, the incorporation of target-triggered 3D DNA walker coupled with hybridization chain reaction (HCR) enables the in-situ assembly of DNA polymers on electrode for loading substantial quencher methylene blue (MB), acquiring significantly decreased photocurrent for sensitive detection. As a result, the proposed biosensor exhibits a linear response to ATP concentrations ranging from 10 fM to 10 nM, with a limit of detection (LOD) of 2 fM (S/N = 3). The practical feasibility of the biosensor is also validated through intracellular ATP detection in MCF-7 and HeLa cells. The proposed design offers a promising approach for trace biomolecule detection in complex biological matrices and broadens the application prospects of self-powered PEC systems.