Carbon dots-thionine modified aptamer-based biosensor for highly sensitive cocaine detection

Due to the application of aptasensors in biosensing, researchers are encouraged to design and develop sensing platforms with greater sensitivity and selectivity. This report introduces an aptasensor whose capture DNA is immobilized on the surface of an ITO electrode modified with a gold nanoparticle (prepared with physical vapor deposition technique). Here, target DNA combined with carbon dots that are modified with thionine to provide an oxidation–reduction redox probe to monitor cocaine. In the presence of cocaine, the aptamer conformational change, was take placed and reduced the distance between thionine and the electrode surface, and increased the charge transfer efficiency. Under optimal conditions our cocaine biosensor shows a dynamic range of 10–70 pM with a detection limit of 0.26 pM. Determination of cocaine in human serum and urine samples shows the practical application of the proposed aptasensor.