Ultrasensitive aptasensor with DNA tetrahedral nanostructure for Ochratoxin A detection based on hemin/G-quadruplex catalyzed polyaniline deposition

An ultrasensitive electrochemical aptasensor with DNA tetrahedral nanostructure (DTN) for Ochratoxin A (OTA) detection was developed based on hemin/G-quadruplex catalyzed polyaniline (PANI) deposition in the presence of H2O2. DTN, which modified with OTA aptamer on top vertex and thiol group on other three vertices, was constructed on the modified electrode surface via Au-S bond and prominent template for PANI deposition owing to their numerous negative charges. The prepared gold nanorods (AuNRs) was used as a carrier to immobilize DTN and promote electron transfer. In the presence of OTA, the aptamer specific for OTA was formed G-quadruplex structure. The hemin/G-quadruplex was formed when hemin was intercalated into G-quadruplex, which had high catalytic activity to catalyze PANI deposition in the presence of H2O2 and amplify DPV signal. The amount of generated PANI was dependent on the number of hemin/G-quadruplex induced by OTA. Therefore, DPV currents was related to the concentration of OTA. The fabricated aptasensor exhibited a good linear response toward OTA over a wide range of concentrations from 0.001 ng/mL to 0.5 ng/mL, and the limit of detection of the proposed aptasensor was 0.26 pg/mL.