Selection of novel aptamers specific for tenuazonic acid and their aptasensors

Tenuazonic acid (TeA) is the most toxic secondary metabolite of Alternaria toxins, which are widely found in vegetables and fruits. In this study, we designed a capture-SELEX method to select aptamers specific for TeA. Real-time quantitative PCR was used to monitor the selection progress, and high-throughput sequencing was performed to analyze the enriched library. The candidate aptamers (Apt1-7) were characterized with isothermal titration calorimetry (ITC) and a T5 exonuclease digestion assay. Next, we fabricated single-labeled and dual-labeled aptasensors based on Apt1 and explored their sensing properties in the food matrix. After 20 rounds of enrichment, the Ct value sharply decreased, indicating enrichment of ssDNA. The analysis of the top 300 sequences revealed 7 families with high homology rates. The ITC assay indicated that Apt1 had a Kd of 0.61 ± 0.07 μM, which was consistent with the T5 exonuclease digestion assay. Compared with the single-labeled aptasensor, the dual-labeled aptasensor had a higher sensitivity with a limit of detection (LOD) of 0.26 μM. This aptasensor had no cross-reactivity with other mycotoxins and exhibited sensing properties in the food matrix. Our study provides a novel aptamer specific for TeA and it can be used to develop a rapid detection kit.