A colorimetric fluorometric dual-mode aptasensor for aflatoxin B₁ detection driven by Au@CeO₂ core-shell nanozymes

A dual-mode aptasensor was engineered for aflatoxin B₁ (AFB₁) detection by functional integration of peroxidase-mimetic Au@CeO₂ core-shell nanostructures with emissive carbon dots (CDs). The Au@CeO₂ nanocomposite, synthesized via spontaneous redox reaction, exhibited enhanced peroxidase-like activity due to abundant Ce³⁺/oxygen vacancies facilitating hydroxyl radical generation. The aptasensor utilizes a competitive binding mechanism, where AFB₁ competed with immobilized Au@CeO₂-CDs-Apt1 probes for binding sites, resulting in inversely proportional colorimetric and fluorescent signals. Under optimized conditions, the biosensor achieved a broad linear detection range (0.001-50 ng/mL) with an ultralow limit of detection (LOD) of 0.0005 ng/mL. The sensor demonstrated excellent selectivity, stability, and reproducibility, and was successfully applied to detect AFB₁ in spiked peanut samples, with recoveries ranging from 98.7 to 116.7%. This work not only advances the design of nanozyme-based biosensors but also provides a rapid, accurate, and field-deployable strategy for monitoring mycotoxins in complex food matrices.