An electrochemical/colorimetric dual-mode sensor for the detection of AFB1 in agricultural products based on CoFe2O4@Au nanoparticles and smartphone imaging

Abstract

An electrochemical/colorimetric dual-model sensor was developed for the specific detection of aflatoxin B1, utilizing the high catalytic activity and magnetic separation properties of CoFe₂O₄@Au along with the conformational alterations in the hairpin DNA structure. The CoFe₂O₄@Au nanocomposite demonstrated excellent peroxidase-like activity, characterized by the relatively low Michaelis constant (K_m = 0.14 mM and 0.94 mM) and the relatively high reaction rate (V_max = 4.43 × 10⁻⁸ M·s⁻¹ and 9.01 × 10⁻⁸ M·s⁻¹). Besides, the visualization results could be obtained using a smartphone in colorimetric mode. The detection linear ranges of the electrochemical workstation, ultraviolet-visible spectrophotometer, and smartphone were 0.001–100 ng mL⁻¹, 0.05–100 ng mL⁻¹, and 0.1–100 ng mL⁻¹, respectively, with corresponding limits of detection were 0.34 pg mL⁻¹, 0.016 ng mL⁻¹, and 0.043 ng mL⁻¹. Furthermore, the matrix effect values of these methods were 91.03 %–112.96 % in peanut, corn, and wheat. This work provided a new direction to explore dual-mode sensor to improve the detection accuracy in real samples.