Magnetic beads-based multicolor colorimetric immunoassay for ultrasensitive detection of aflatoxin B1

Aflatoxin B-1 (AFB(1)) is one of the most toxic, mutagenic and carcinogenic mycotoxin, widely exists in contaminated food, grains and feedstuff products. In this study, a novel magnetic beads multicolor colorimetric immunoassay (MBMCIA) based on Au@Ag nanorods (Au@Ag NRs) is proposed to visual detect ultralow concentration of AFB(1) with high-resolution by the naked-eye. To design the MBMCIA system, AFB(1)-BSA conjugates were first coated on the surface of magnetic beads (MBs), then alkaline phosphatase (ALP) as a bridge between immunoassay and color reaction was used for catalytic hydrolysis of ascorbic acid-phosphate to generate reductive ascorbic acid. Finally, the yielded ascorbic acid could reduce silver ions to grow a silver coating on the surface of gold nanorods to generate Au@Ag NRs, which leads to the bule-shifted longitudinal absorption peak of Au NRs, accompanying with a series of perceptible color change. Under the optimal conditions, the proposed MBMCIA exhibited good sensitivity and specificity for the detection of AFB(1) with the detection limit as low as 5.7 pg/mL. Meanwhile, the MBMCIA was also applied for the analysis of AFB(1) in spiked wheat samples, the obtained recoveries range from 99.1% to 104.3% with relative standard deviation (RSD) less than 7.05% were acceptable. The proposed MBMCIA integrates separated, enriched, anti-interference and signal read-out into one, which opens up a new avenue for an on-site visual food safety inspection or environmental monitoring. (C) 2020 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.

Automated summary

A novel magnetic beads multicolor colorimetric immunoassay (MBMCIA) based on Au@Ag nanorods was proposed for the visual detection of ultralow concentration of Aflatoxin B-1 (AFB(1)). The method exhibited good sensitivity and specificity, making it suitable for applications in food safety inspection and environmental monitoring.