Magnetic Rice Husk Biochar for AFB1 Enrichment in Water, Rice and Maize: A Wash-Free Sensitivity Improvement Strategy for Immunochromatographic Test Strip

The fungi in water distribution systems and drinking water have already been reported and can produce mycotoxins. In this study, a wash-free immunochromatographic test strip (ICTS) based on magnetic rice husk biochar for the ultrasensitive detection of Aflatoxin B1(AFB1) in water and grain has been developed. Magnetic rice husk biochar (MB) was a green nanomaterial, which was synthesized from rice hull and characterized. Fe₃O₄ was formed within the amorphous and granular MB. Used as an enrichment tool for AFB1 in water and food, the MB-based ICTS method could detect MB-AFB1 complex without washing steps depending on the high affinity of the antibody. Compared with the diluted method, the developed ICTS method acquired sensitivity improvement 4-fold for the qualitative detection of AFB1 in rice. The absorption process was finished within 5 min. Interference of rice matrix showed minimum effect compared with brown rice and maize. This study provided a facile approach to prepare MB from rice husk for effective enrichment/removal of AFB1 in water and based on it, the wash-free magnetic pretreatment method will be an alternative tool for multiple target enrichment and quantitative determination in the future.