Magnetic Relaxation Switching Immunoassay Based on Hydrogen Peroxide‐Mediated Assembly of Ag@Au–Fe<sub>3</sub>O<sub>4</sub> Nanoprobe for Detection of Aflatoxin B1
Yongzhen Dong, Cong‐Ying Wen, Yongxin She, Yu Zhang, Yiping Chen, Jingbin Zeng
Abstract
Abstract Magnetic relaxation switching (MRS) sensors have shown great potential in food safety monitoring due to their high signal‐to‐noise ratio and simplicity, but they often suffer from insufficient sensitivity and stability due to the lack of excellent magnetic nanoprobes. Herein, dumbbell‐like Au–Fe 3 O 4 nanoparticles are designed as magnetic nanoprobes for developing an aflatoxin B1‐MRS immunosensor. The Fe 3 O 4 portion in the Au–Fe 3 O 4 nanoparticles functions as the magnetic probe to provide transverse relaxation signals, while the Au segments serve as a bridge to grow Ag shell and assemble the Au–Fe 3 O 4 nanoparticles, thus modulating transverse relaxation time of surrounding water molecular. The formation of Ag@Au–Fe 3 O 4 is triggered by hydrogen peroxide. After degraded by horseradish peroxidase, hydrogen peroxide reduces Ag + to Ag nanoparticles which assemble dispersed Au–Fe 3 O 4 to aggregated Ag@Au–Fe 3 O 4 , thus dramatically improving the sensitivity of traditional MRS sensor. Combined with competitive immunoreaction, this Ag@Au–Fe 3 O 4 –MRS immunosensor can detect aflatoxin B1 with a high sensitivity (3.81 pg mL −1 ), which improved about 21 folds and 9 folds than those of enzyme‐linked immunosorbent assay and high‐performance liquid chromatography (HPLC), respectively. The good consistency with HPLC in real samples detection indicates the good accuracy of this immunosensor. This Ag@Au–Fe 3 O 4 –MRS immunosensor offers an attractive tool for detection of harmful substances.