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Determination of ochratoxin a with a DNA aptamer.

This work describes the identification of an aptamer that binds with high affinity and specificity to ochratoxin A (OTA), a mycotoxin that occurs in wheat and other foodstuffs, and a quantitative detection method for OTA based on the use of this aptamer. Aptamers are single-stranded oligonucleotides selected in vitro to bind to molecular targets. The aptamer selected in this work exhibited a dissociation constant in the nanomolar range and did not bind compounds with structures similar to OTA such as N-acetylphenylalanine or warfarin. The aptamer bound with a 100-fold less affinity to ochratoxin B. The selected aptamers could be used for the determination of ppb quantities of OTA in naturally contaminated wheat samples. Further work is ongoing to broaden the application demonstrated here with the development of sensors, affinity columns, and other analytical systems for field and laboratory determination of this toxin in food and agricultural products.