A　simple　and　feasible　homogeneous　electrochemical　sensing　protocol　was　developed　for　the　detection　of　ochratoxin　A　(OTA)　in　foodstuff　on　the　immobilization-free　aptamer-graphene　oxide　nanosheets　coupling　with　DNase　I-based　cycling　signal　amplification.　Thionine-labeled　OTA　aptamers　were　attached　to　the　surface　of　nanosheets　because　of　the　strong　noncovalent　binding　of　graphene　oxide　nanosheets　with　nucleobases　and　aromatic　compounds.　The　electronic　signal　was　acquired　via　negatively　charged　screen　printed　carbon　electrode　(SPCE)　toward　free　thionine　molecules.　Initially,　the　formed　thionine-aptamer/graphene　nanocomposites　were　suspended　in　the　detection　solution　and　far　away　from　the　electrode,　thereby　resulting　in　a　weak　electronic　signal.　Upon　addition　of　target　OTA,　the　analyte　reacted　with　the　aptamer　and　caused　the　dissociation　of　thionine-aptamer　from　the　graphene　oxide　nanosheets.　The　newly　formed　thionine-aptamer/OTA　could　be　readily　cleaved　by　DNase　I　and　released　target　OTA,　which　could　retrigger　thionine-aptamer/graphene　nanocomposites　with　target　recycling　to　generate　numerous　free　thionine　molecules.　Free　thionine　molecules　were　captured　by　negatively　charged　SPCE,　each　of　which　could　produce　an　electrochemical　signal　within　the　applied　potentials.　Under　optimal　conditions,　graphene-based　aptasensing　platform　could　exhibit　good　electrochemical　responses　for　the　detection　of　OTA　at　a　concentration　as　low　as　5.6　pg/mL.　The　reproducibility,　precision　and　selectivity　of　the　system　were　acceptable.　Importantly,　the　method　accuracy　was　comparable　with　commercialized　OTA　ELISA　kit　when　using　for　quantitative　monitoring　of　contaminated　wheat　samples.　(C)　2015　Elsevier　B.V.　All　rights　reserved.