DNA cube-gated ratiometric ECL/SERS biosensor for APE1 via HCR-driven interfacial reconstruction

A dual-mode ratiometric electrochemiluminescence/surface-enhanced Raman scattering (ECL/SERS) biosensor was developed for sensitive monitoring of apurinic/apyrimidinic endonuclease 1 (APE1) activity. A hierarchical Ti₃C₂/CsPbBr₃@PDA@Au nanocomposite was engineered as an integrated transducer, in which conductive Ti₃C₂ MXene enables efficient charge transport, CsPbBr₃ serves as an anodic ECL luminophore, and PDA-stabilized Au domains provide plasmonic hot spots and Au-S anchoring sites for DNA immobilization. A wireframe DNA cube was assembled on the Au-decorated interface and further functionalized with a hairpin capture module to implement a low-background gating architecture. Upon APE1 cleavage of an AP-site substrate, an initiator was generated to trigger hybridization chain reaction (HCR) amplification, yielding long DNA concatemers that were subsequently captured by the cube-hairpin scaffold. This programmed capture reconstructed the near-electrode microenvironment and produced an anti-correlated output: progressive ECL attenuation ("ECL-off") accompanied by SERS enhancement ("SERS-on"). A ratiometric readout was defined as R=I_SERS/I_ECL, providing self-referenced quantification with improved tolerance to baseline drift and electrode-to-electrode variability. The sensor exhibited a wide working range for APE1 (1×10^-8-1×10^-2 U/mL) and was further validated by selectivity, repeatability, fabrication reproducibility, operational/storage stability, and Raman mapping-based uniformity assessments. This work establishes a causality-locked amplification-capture strategy to couple DNA repair enzyme activity with a perovskite-plasmonic dual-mode interface, offering a useful design concept for ratiometric biosensing in complex matrices after appropriate target-specific optimization.