Fabrication of Electro-active Nano-trans Surfaces to Design Label Free Aptasensor for Ochratoxin-A Detection

Abstract

With increased awareness of nutrition and the advocacy for healthier food choices, there exists a great demand for a simple, low-cost, label free and easy-to-use assays that can reliably detect toxins in agriculture products. In this regard, a simple and highly sensitive electrochemical sensing platform based on the structural switching signaling of aptamer has been developed for the detection of smaller molecules using Ochratoxin A as a model analyte. Pencil electrode was first modified with highly conductive Graphene oxide/Fe3O4NP/PPY composite and then was self-assembled with aptamer using EDC/NHS technique. This immobilized nanoprobe provided gates of tunnels for the effective electron flow showing higher peak current. The introduction of the target analyte (OTA) triggered switching of the aptameric structure resulting in the decrement of the redox current. This decrease was proportional to the analyte concentration, thus featuring signal on/off strategy. This proposed transducing design showed a dynamic linear range (10 pg/mL-200ng/mL) with Limit of detection and limit of quantification of 5pg/mL and 40pg/mL respectively. We demonstrate this transducing design as a general inexpensive and reproducible method to specifically detect a wide variety of analytes by selecting a suitable biorecognation element. Real sample analysis was performed for the real time approach and results collected are in agreement with practical application.