Selection of a DNA aptamer for aflatoxin B1 and the development of a lateral flow assay for the detection of aflatoxins in spiked peanut extract

Abstract

Aflatoxins are a family of highly toxic compounds that contaminate food pre- and post-harvest, negatively impacting the agroeconomic system. Their severe acute and chronic health effects pose a threat to human health. Interest has been shown in developing rapid, reliable and cost-effective on-site detection tools for aflatoxins. A capture SELEX experiment to discover aptamers for total aflatoxin (B1, B2, G1 and G2) was conducted. The selection library was designed to be immobilized to a solid support matrix through complementary binding of a capture probe to the central capture region of the library template. From this selection the aptamer candidate DZA3 was selected because of its high affinity for AFB1, the most toxic of the aflatoxins. The dissociation constant (K_d) was elucidated using microscale thermophoresis which yielded results of K_d: 42.1 ± 23.8 nM. The aptamer was integrated into a colorimetric solution assay that achieved a detection limit as low as 2.28 nM in water. For ease and portability, a colorimetric lateral flow assay was developed that was tested in a non-complex sample and in spiked peanut extract. The limits of detection achieved were 14.67 nM in water and 1.90 μM (5.93 mg kg⁻¹) in the spiked peanut extract. The limits of quantification achieved in water and the spiked peanut extract were 44.44 nM and 5.75 μM (17.80 mg kg⁻¹), respectively.