Dual-FRET aptasensor for rapid screening of Ochratoxin A in food samples

Abstract

Simple, low cost, and sensitive OTA screening method is important for food safety control. The discovery of the OTA aptamer enabled the development of various aptasensors, but the structural change caused by target binding is not appreciable enough, thus limiting the sensitivity. The introduction of various nanomateirals could amplify the structure change, but such aptasensors are difficult to be standardized, thus is not suitable for screening analysis. Herein, we proposed a full DNA-based dual-FRET aptasensor, in which the aptamer was rigidified to amplify the OTA-induced structure change. Meanwhile, a dual FRET strategy was employed to increase the OTA detection sensitivity. Upon both experimental and theoretical selection, aptamer OBA33 was selected, leading to a detection limit of 2.1 nM that is lower than the limit set by Chinese National Food Safety Standard (12 nM), thus is appealing for screening of potential OTA-positive cases in a large number of rice samples. To facilitate rapid screening analysis, a mini 3D-printed sensor device was constructed by integrating LED excitation, cellphone camera image taking, and RGB extraction. Due to the technological maturity of DNA production, the proposed aptasensor could be easily standardized for fast OTA screening analysis (15 min).