Highly sensitive magnetic relaxation sensing method for aflatoxin B1 detection based on Au NP-assisted triple self-assembly cascade signal amplification

Highly sensitive detection of aflatoxin B1 (AFB1) is of great significance because of its high toxicity and carcinogenesis. We propose a magnetic relaxation sensing method based on gold nanoparticles (Au NPs)-assisted triple self-assembly cascade signal amplification for highly sensitive detection of AFB1. Both AFB1 antibody and initiator DNA (iDNA) are labeled on Au NPs to form Ab-Au-iDNA probe. iDNA is enriched by Au NPs to achieve first signal amplification. Different amounts of Ab-Au-iDNA were bound with AFB1 antigen by indirect competitive immunoassay, and then hybridization chain reaction event was initiated by iDNA to produce long hybridization chain reaction products to enrich more horseradish peroxidase-streptavidin for the second signal amplification. Dopamine could be rapidly converted to polydopamine by HRP catalysis, which is used as the third signal amplification. The Fe3+ solution, providing paramagnetic ions with a strong magnetic signal, could be adsorbed by the polydopamine due to the formation of coordination bonds of phenolic hydroxyl groups with Fe3+. This effective interaction between polydopamine and Fe3+ significantly changes the transverse relaxation time signal of Fe3+ supernatant solution, which can be used as a magnetic probe for highly sensitive detection of AFB1. The sensor exhibited high specificity and sensitivity with a detection limit of 0.453 pg/mL owing to the Au NP-assisted triple self-assembly cascade signal amplification strategy. It has been successfully employed for AFB1 detection in animal feed samples with consistent results of enzyme linked immune sorbent assay and highperformance liquid chromatography.