Two-dimensional　(2D)　MoS2　is　found　to　possess　different　affinities　for　ssDNA　and　dsDNA.　This　finding　is　exploited　in　an　amperometric　aptamer-based　method　for　the　determination　of　the　mycotoxin　ochratoxin　A　(OTA).　Initially,　a　dsDNA　probe　(formatted　through　the　hybridization　of　OTA-aptamer　with　an　auxiliary　DNA)　is　self-assembled　on　a　gold　electrode.　Upon　introduction　of　OTA,　it　will　bind　to　the　aptamer　and　cause　the　unwinding　of　dsDNA,　while　the　auxiliary　DNA　(with　single-stranded　structure)　remains　on　the　electrode.　Since　the　affinity　of　2D　MoS2　for　ssDNA　is　considerably　larger　than　that　for　dsDNA,　it　will　be　adsorbed　on　the　electrode　by　binding　to　the　auxiliary　DNA.　Notably,　2D　MoS2　possesses　peroxidase-like　activity.　Hence,　it　can　catalyze　the　amplification　of　electrochemical　signal　of　the　hydroquinone/benzoquinone　redox　system.　Under　optimal　conditions,　the　amperometric　signal　(best　measured　at　−0.2 V　vs.　SCE)　increases　with　increasing　OTA　concentration　in　the　range　from　0.5 pg·mL−1　to　1.0 ng·mL−1,　with　a　lower　detection　limit　of　0.23 pg·mL−1.　The　method　was　applied　to　the　determination　of　OTA　in　spiked　red　wine.　[Figure　not　available:　see　fulltext.].　©　2018,　Springer-Verlag　GmbH　Austria,　part　of　Springer　Nature.