Magnetically controlled electrochemical/visual colorimetric biosensor for ultrasensitive detection of aflatoxin B1 in peanuts based on a novel H-shaped reactor triggered dual signal amplification

: Aflatoxin B1 (AFB1) can be present in moldy grains, nuts, oil crops, and their processed by-products, posing a threat to food safety and human health. Therefore, sensitive and efficient detection of trace AFB1 is of great significance for early intervention in protection of food safety. In this research, an aptamer was used as the recognition agent for AFB1, a novel magnetically controlled electrochemical-visual colorimetric dual-mode AFB1 biosensing strategy was developed. H-shaped device consisting of a left cell and a right cell was designed, with the anodic aluminum oxide (AAO) membrane nanochannel in between. Under magnetic control, specific recognition of AFB1 by the aptamer in the left cell triggers DNA hybridization chain reaction (HCR) in the right cell, forming a glucose oxidase and peroxidase-like DNA G-quadruplex cascade catalytic structure, enabling the determination of AFB1 via glucose catalysis. This method incorporates dual signal amplification technology (HCR and enzyme cascade catalytic) and achieves spatial separation between AFB1 recognition and detection, thereby effectively reducing background interference and improving sensitivity. Using the electrochemical mode (Differential pulse voltammetry), the method achieved low limit of detection (LOD) of 4.2 × 10 -7 ng/mL, wide linear range of 10 -6 -10 2 ng/mL, excellent selectivity and anti-interference performance. Using the visual colorimetric mode, the LOD was as low as 3.4 × 10 -7 ng/mL and the linear range was 10 -6 -10 4 ng/mL. This work proposes a general dual-mode biosensing strategy and provides a promising approach for highly sensitive and efficient detection of trace-level targets in complex samples.