Ultrasensitive Photoelectrochemical Assay for DNA Detection Based on a Novel SnS₂/Co₃O₄ Sensitized Structure

In this work, an ultrasensitive photoelectrochemical (PEC) assay was established for sensitive DNA detection based on a novel SnS₂/Co₃O₄ sensitized structure as a photoactive matrix and benzo-4-chlorohexadienone (4-CD) precipitate as a signal quencher. Noticeably, the photoelectric conversion efficiency of the SnS₂/Co₃O₄ sensitized structure was dramatically enhanced due to the effective sensitization of Co₃O₄ toward SnS₂, thus attaining an intense photocurrent response, which was sixfold higher than that of pristine SnS₂. Additionally, with the assistance of Nt.BstNBI enzyme-assisted target cycling process, a limited amount of target DNA (a fragment of p53 gene) could be converted into extensive output DNA, which could hybridize with capture DNA to yield abundant DNA duplex for loading mimetic enzyme manganese porphyrin (MnPP). Subsequently, 4-chloro-1-naphthol (4-CN) could be catalyzed to form 4-CD precipitate by MnPP on the modified electrode surface with the existence of H₂O₂. Then, the 4-CD precipitate severely hampered electron transfer, causing a prominently diminished photocurrent response for DNA determination. The elaborated PEC assay not only extended the application of SnS₂ in the PEC biosensing field but also manifested a wide linear range of 100 aM to 1 nM with a low detection limit of 30 aM, exhibiting enormous potential for the detection of various biomarkers or other targets in bioanalysis and disease diagnosis fields.