Development of electrochemical aptasensor using Au octahedra and graphene as signal amplification
A novel electrochemical aptasensor was constructed for ochratoxin A (OTA) detection based on Au octahedra and graphene (GR) as signal amplification strategy. Au octahedra with eight triangle faces and sharp corners was prepared and acted as the carrier for connecting more thionine (Th) and complementary DNA (cDNA) to form Th-Au octahedra-cDNA. The Th-Au octahedra-dsDNA formed by hybridizing OTA aptamer with cDNA. GR with high surface area and good conductivity immobilized more biomolecules and facilitated the electron transfer on the electrode surface. Th-Au octahedra-dsDNA was immobilized on the GR/GCE surface, producing a large initial peak current. In the presence of OTA, the formation of aptamer-OTA complex induced the release of Th-Au octahedra-cDNA from the electrode surface and reduced the electrochemical signal of Th. The proposed aptasensor exhibited a wider linear range from 0.001 to 5 ng/mL with a lower detection limit of 0.13 pg/mL, and showed the good selectivity against common interferences including AFB1, ZEA and FB1.