Screening of a High-Affinity Aptamer for Aflatoxin M 1 and Development of Its Colorimetric Aptasensor.

Aflatoxin M 1 (AFM 1 ), a secondary metabolite of Aspergillus spp., is highly toxic and widely present in food matrices. Therefore, the detection of AFM 1 is of great importance for the protection of food safety. In this study, a five-segment sequence was designed as the initial library. Graphene oxide-SELEX (GO-SELEX) was applied to screen AFM 1 . After seven rounds of repeated screening, affinity and specificity assays showed that aptamer 9 was the best candidate for AFM 1 . The dissociation constant ( K d ) of aptamer 9 was 109.10 ± 6.02 nM. To verify the efficiency and sensitivity aptamer for the detection of AFM 1 , a colorimetric sensor based on the aptamer was constructed. The biosensor showed good linearity in the range of AFM 1 concentration of 0.5-500.0 ng/mL with a detection limit of 0.50 ng/mL. This colorimetric method was successfully used for the detection of AFM 1 in milk powder samples. Its detection recovery was 92.8-105.2%. This study was conducted to provide a reference for the detection of AFM 1 in food.