A multicolor aptasensor based on target-induced anti-etching gold nanorod for visible detection of aflatoxin B1

Foods contaminated with aflatoxin B1 (AFB1) pose a serious threat to humans, so rapid and sensitive detection of AFB1 plays an important role in public health. In this work, we developed a multicolor aptasensor based on target-mediated anti-etching of gold nanorods (AuNRs) for on-site visible detection of AFB1. The target was used as a competitor that competed with a cDNA probe labeled by horse radish peroxidase (cDNA-HRP) to bind with the aptamer coated in a microplate. The sensing mechanism was based on regulating the etching process of AuNRs upon the addition of different concentrations of AFB1. In the absence of AFB1, the AuNRs solution undergoes a distinct change from red to pink due to the etching effect of TMB2+ generated by a specific redox reaction catalyzed by the cDNA-HRP. However, in the presence of AFB1, the specific binding between AFB1 and aptamer made cDNA-HRP free out of the microplate, inhibiting the etching of AuNRs. Consequently, a redshift of longitudinal localized surface plasmon resonance (LSPR) and color alterations can be observed along with increasing the concentration of AFB1. The LSPR for visual estimation limits were 0.46 ng/mL. A good linear relationship between the wavelength shift and the concentration of AFB1 was achieved from violet to light green in the range of 1-1000 ng/mL. The established aptasensor displayed excellent detection performance, which was suitable for on-site analysis of AFB1 in actual food samples, and provided a new idea of immediate visualization detection for food hazardous factors.