A dual-mode ECL/SERS biosensor for sensitive and self-validated detection of APE1 via X-shaped DNA-triggered cascade amplification and a perovskite–Au/MXene interface

Apurinic/apyrimidinic endonuclease 1 (APE1) is a key DNA repair enzyme and an important biomarker associated with genome stability and disease progression. In this work, we developed a dual-mode biosensor for sensitive and self-validated detection of APE1 by integrating an APE1-responsive cascade amplification module with a perovskite–Au/MXene (PAM)-supported electrochemiluminescence/surface-enhanced Raman scattering (ECL/SERS) transduction interface. In the upstream process, APE1 specifically cleaved the AP sites within an X-shaped DNA recognizer, generating trigger strands that initiated strand displacement amplification (SDA) and Zn²⁺-assisted DNAzyme cleavage, thereby releasing abundant enhancer strands. In the downstream process, the generated enhancer strands were captured by the PAM-modified electrode and further induced interfacial recruitment of reporter units, which simultaneously suppressed the ECL signal and enhanced the SERS response. As a result, APE1 activity was converted into an opposite-response dual-mode output with improved analytical reliability. Under the optimized conditions, the proposed biosensor exhibited a wide detection range from 0.005 to 2.0 U/mL and a low detection limit of 4.91 × 10⁻³ U/mL. In addition, the sensing platform showed excellent selectivity toward APE1 over various interfering nucleases and proteins, together with good repeatability, fabrication reproducibility, operational stability, storage stability, and favorable spatial uniformity of the SERS-active interface. By coupling efficient target-triggered nucleic-acid amplification with interface-confined dual-mode signal transduction, this work provides a promising strategy for sensitive and self-validated analysis of APE1 and offers a useful framework for the construction of dual-mode biosensors for other enzymatic biomarkers.