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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]

Zearalenone (ZEN) contamination has attracted global attention of the food industry because of its toxicity to human body, so sensitive and rapid ZEN assays are critically important. Herein, methylene blue (MB) and Ag+ were used as dual-signal probes to design a ratiometric electrochemical aptasensor for facilely and accurately detection of ZEN, and an Au@Pt/Fe-N-C nanocomposites-induced signal amplification strategy was introduced to improve the sensitivity of the aptasensor. The Au@Pt/Fe-N-C nanocomposites had larger surface area and higher conductivity than single component materials. Firstly, DNA1 was modified on the gold electrode (AuE), so the signal probe Ag+ can produce a strong I Ag+ by forming C-Ag+-C structure with DNA1. Simultaneously, the system MB-Au@Pt/Fe-N-C-dsDNA (containing aptamer and DNA2) cannot modify to AuE to obtain I MB. The aptasensor was incubated with ZEN that can compete with aptamer, and the released MB-Au@Pt/Fe-N-C-DNA2 can be modified on AuE by hybridization between DNA1 and DNA2, so as to generate a strong I MB. Au@Pt or Fe-N-C. The intensity of I Ag+ decreased because it cannot combine with DNA1. The signal ratio I MB /I Ag+ exhibited a good linear relationship with lgC ZEN in the concentration of ZEN in the ranging of 1 × 10−5-10 ng/mL, and the limit of detection (LOD) and limit of quantitation (LOQ) were calculated as 5 fg/mL and 16.7 fg/mL, respectively. The successfully determination of ZEN in corn flour samples demonstrated that the ratiometric electrochemical aptasensor had excellent veracity, reliability and potential application prospects. A methylene blue and Ag+ ratiometric electrochemical aptasensor with two simultaneous relative change signal probes was developed, and the Au@Pt/Fe-N-C nanocomposites-assisted signal amplification strategy was used to improve the sensitivity of the method. The biosensor had a detection limit as low as 5 fg/mL. [Display omitted] • A novel Au@Pt/Fe-N-C nanocomposites was prepared as an electrochemical signal amplification strategy. • A ratiometric electrochemical aptasensor was constructed based on methylene blue and Ag+ as ratio signal probes. • The proposed aptasensor was successfully applied to monitor zearalenone in corn flour samples. • Ratiometric signal sensor has excellent veracity, reliability and potential application prospects. [ABSTRACT FROM AUTHOR]