Horseradish peroxidase-catalyzed formation of polydopamine for ultra-sensitive magnetic relaxation sensing of aflatoxin B1

Aflatoxin B1 as one of the most toxic mycotoxins poses a major health risk to humans and animals. Highly sensitive detection methods of aflatoxin B1 are urgently required because of its low abundance in biological samples. In this work, we developed a magnetic relaxation sensing strategy using enzyme-catalyzed formation of polydopamine for signal amplification. Horseradish peroxidase can catalyze the reaction to generate polydopamine that assembles magnetic nanoparticles for magnetic relaxation sensing with a high signal-to-noise ratio. Combined with the specific antigen-antibody interaction, this magnetic sensor enables fast and ultra-sensitive detection of aflatoxin B1 by using transverse relaxation time (T2) as a readout. Under optimized conditions, the linear range of this magnetic sensor for detecting aflatoxin B1 is from 10 pg/mL to 10 ng/mL, and the limit of detection is 0.35 pg/mL. This sensor has been challenged for the quantitative analysis of aflatoxin B1 in animal feed samples that is promising for real-world applications.