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In this work, a kind of homogeneous electrochemical aptasensor based on DNA assembly was designed to detect zearalenone (ZEN). The three DNA strands of ZEN aptamer (Apt), complementary strand DNA1, and complementary strand DNA2 are first mixed to form DNA duplex structure, which cannot be cleaved by RecJf Exonuclease (RecJf Exo) and hinders the electron transfer after addition to the electrode surface. With the existence of ZEN, the combination of ZEN and Apt destroys the duplex structure, and RecJf Exo can catalyze the cleavage of Apt to form short DNA strands, which accelerates the electron transfer after addition to the electrode surface. According to the current difference with or without ZEN, the detection purpose is achieved. The linear relationship between I and LgCZEN was found in the range of 5.0 × 10−6 ng/ml to 50 ng/ml, and the detection limit is as low as 0.51 fg/ml. The prepared sensor showed high selectivity, favorable repeatability, and reproducibility and was effectively used for testing the spiked corn flour and beer samples. [ABSTRACT FROM AUTHOR]

A complementary DNA (cDNA) was designed to simultaneously hybridize with the ochratoxin A (OTA) aptamer and the fumonisin B1 (FB1) aptamer to form a unique Y-shaped DNA structure and to achieve simultaneous detection. Gold nanorods (AuNRs) were used to immobilize thionine (Th), thiolated ferrocene (Fc), thiolated OTA aptamer (Apt1), and thiolated FB1 aptamer (Apt2), to form an amplified signal element and a recognition element. The Apt1-AuNRs-Th complex and the Apt2-AuNRs-Fc complex hybridize with cDNA to form a unique Y-DNA structure on a gold electrode. This produces two initial electrochemical signals [with 177 μΑ cm−2 near −0.2 V, and 3121 μΑ cm−2 near +0.46 V (vs. Ag/AgCl)] by differential pulse voltammetry. Upon addition of 0.1 ng mL−1 OTA and 0.1 ng mL−1 FB1, the aptamers bind the two toxins. This results in the release of Apt1-AuNRs-Th and Apt2-AuNRs-Fc, so the peak currents densities decrease to 115 μΑ cm−2 and 209 μΑ cm−2. The assay allows simultaneous determination of OTA and FB1 in the 1.0 pg·mL−1 to 100 ng·mL−1 concentration ranges, with LODs of 0.47 and 0.26 pg·mL−1. The assay is reproducible, stable and specific. It was applied to the determination of OTA and FB1 in spiked beer, with recoveries between 89.0% and 102.0%. [ABSTRACT FROM AUTHOR]