A dual signal ratio electrochemical sensor based on DNA tetrahedrons and bimetallic nanocomposites for AFB1 analysis

NGR-HP-AgPt and DNA tetrahedrons build a 3D track, avoiding probe entanglement. • Exo III-driven DNA walker achieves dual-signal ratiometric sensing of AFB 1 . • The built-in self-calibration effectively eliminates false-positive artifacts. • Ultrasensitive assay (LOD 73.99 fg/mL) successfully applied in complex matrices. Given the hepatotoxicity and widespread contamination of Aflatoxin B 1 (AFB 1 ), developing ultra-sensitive, anti-interference analytical platforms is paramount for public health. Herein, a dual signal ratio electrochemical sensing platform for accurate AFB 1 analysis was constructed integrating DNA tetrahedrons (TNDA), a dynamic DNA walker, and nitrogen-doped graphene oxide-supported hollow silver-platinum bimetallic nanospheres (NGR-HP-AgPt). The NGR-HP-AgPt cavity provides a uniform microenvironment, synergistically promoting catalytic effects to significantly accelerate interfacial electron transfer. Simultaneously, rigid 3D TNDA prevent spatial probe entanglement, providing a well-oriented track. To avoid false-positive artifacts in complex matrices, a competitive binding strategy is employed. Upon target recognition, AFB 1 displaces a complementary sequence (DNA1) from the aptamer. The released DNA1 acts as a walking strand, hybridizing with signal probes (Cd 2+ -DNA2). Subsequently, Exonuclease III initiates the DNA walker, continuously cleaving probes to amplify the ratiometric signal variation for reliable self-calibration. Under optimal conditions, this sensor exhibits a broad linear range from 2 × 10 −4 to 20 ng/mL, with an ultra-low detection limit of 73.99 fg/mL. Furthermore, its practical utility and high accuracy were successfully validated in complex food and medicinal matrices, yielding consistent results with the standard HPLC-FL method. This work broadens the robust design paradigm of anti-interference biosensing. Download: Download high-res image (296KB) Download: Download full-size image