On　the　basis　of　aptamer-based　rolling　circle　amplification　(RCA)　and　magnetic　beads　(MBs),　a　highly　sensitive　electrochemical　method　was　developed　for　the　determination　of　Ochratoxin　A　(OTA).　Initially,　an　amino-modified　capture　DNA　was　immobilized　onto　MBs　for　the　following　hybridization　with　an　OTA　aptamer　and　a　phosphate　labeled　padlock　DNA.　In　the　presence　of　OTA,　the　aptamer　would　dissociate　from　the　bioconjugate,　and　the　padlock　DNA　would　subsequently　hybridize　with　the　capture　DNA　to　form　a　circular　template　with　the　aid　of　the　T4　ligase.　Next,　capture　DNA　would　act　as　primer　to　initiate　a　linear　RCA　reaction　and　hence　generate　a　long　tandem　repeated　sequences　by　phi29　DNA　polymerase　and　dNTPs.　Then,　two　quantum　dots　(QDs)　labeled　DNA　probes　were　tagged　on　the　resulted　RCA　product　to　indicate　the　OTA　recognition　event　by　electrochemical　readout.　This　strategy,　based　on　the　novel　design　of　OTA-mediated　DNA　circularization,　the　combination　of　RCA　and　double　signal　probes　introduction,　could　detect　OTA　down　to　the　level　of　0.2　pg　mL(-1)　with　a　dynamic　range　spanning　more　than　4　orders　of　magnitude.　The　proposed　approach　is　tested　to　determine　OTA　in　red　wines　and　shows　good　application　potential　in　real　samples.　(C)　2011　Elsevier　B.V.　All　rights　reserved.