Nicking-controlled biosensor: Integrating DNA Walker-RCA circuit with trimetallic nanozyme for aflatoxin B₁ detection

Aflatoxin B₁ (AFB₁) is a highly toxic mycotoxin that poses serious threats to global food safety and public health. The ingestion of these contaminated products causes substantial risks to both food safety systems and public health. Despite the availability of various detection techniques, the requirement for highly sensitive analysis of AFB₁ contamination in agricultural products continues to drive demand for improved methodologies.

In this work, a novel electrochemiluminescence (ECL) biosensor was developed for the sensitive detection of aflatoxin B₁ (AFB₁) by integrating a galvanic replacement-synthesized Au@Ag-Pt nanozyme with a DNA walker-controlled rolling circle amplification (RCA) circuit. The core-shell Au@Ag-Pt nanozyme exhibits superior conductivity, enhanced peroxidase activity, and electrocatalytic performance, leading to a 17.67-fold amplification of ECL. A target-responsive "signal-off" mechanism was established based on AFB₁-induced DNA structural switching and enzymatic cleavage, which effectively suppresses the RCA process and reduces the immobilization of nanozyme labels. The biosensor achieved a wide linear range from 5 × 10^-11 to 5 × 10^-5 mg/mL with a detection limit of 2.72 × 10^-11 mg/mL. It shows high specificity against common interfering mycotoxins, good reproducibility, and satisfactory recoveries ranging from 82.7% to 110.5%.

This work not only provides a reliable platform for mycotoxin monitoring but also advances nanozyme engineering in biosensing, offering significant promise for food safety and environmental applications.