Ochratoxin b

OTA, ochratoxin B (OTB), ochratoxin C (OTC) and aflatoxin B1 (AFB1) were purchased from Pribolab Co., Ltd. (Qingdao, China). N-methyl-mesoporphyrin IX (NMM) was bought from JKchemical Co., Ltd. (Beijing, China), stored at −20 °C in the dark before use. The ssDNA used in the experiments were synthesized and further purified by Sangon Biotech Co., Ltd. (Shanghai, China). The sequence of ssDNA (H1) is 5′-GAT CGG GTG TGG GTG GCG TAA AGG GAG CAT CGG ACA CGC CAC CCA CAC-3′, where the italic sequences are OTA aptamer. The sequence of ssDNA (H2) is 5′-CCA CAC CCG ATC CTG GGA GGG AGG GAG GGG TGT GGG TGG CG-3′, and some of which can form G-quadruplex structure. By dissolving the DNA strands in 10 mM Tris buffer (200 mM NaCl, 20 mM MgCl₂, pH 7.4) to obtain the DNA stock solution, and then stored at −4 °C before use. The ultra pure water used in our experiment was purified by a Milli-Q system (18 MΩ cm). 96-Well microplates were purchased from Lingyi Biotech Co., Ltd. (Shanghai, China).

All DNA strands listed in Table 1 were synthesized and purified by Sangon Biotech Inc. (Shanghai, China). Aflatoxin B1 (AFB1), ochratoxin A (OTA), ochratoxin B (OTB), fumonisin B1 (FB1), fumonisin B2 (FB2), and zearalenone (ZAE) were purchased from Pribolab (Qingdao, China). Beer and corn flour were bought from a local supermarket. Assay buffer was 10 mM Tris-HCl (pH 7.5) solution containing 50 mM NaCl, 50 mM MgCl₂, and 0.1% Tween20. Black 96-wells microplates were purchased from Thermo Fisher Scientific Inc. (Waltham, USA). All reagents used for experiments were analytical reagents. Solutions were prepared with ultrapure water (>18.2 MΩ·cm) from a Purelab Ultra Genetic Elga Labwater system (High Wycombe, UK).