DNA aptamer-based QDs electrochemiluminescence biosensor for the detection of thrombin

A novel biosensor for the detection of thrombin was developed by using QDs electrochemiluminescence (ECL) technique. The thiol-terminated aptamer with 15 nucleotides (probe I) was first immobilized on Au electrode, and then thrombin was imported to form the aptamer–thrombin bioaffinity complexes. Another 5′-biotin modified aptamer (29 nucleotides, probe II) was next hybridized with the combined thrombin to form a sandwich type structure. Streptavidin modified QDs (avidin–QDs) were bound to probe II via the biotin–avidin-system. The QDs ECL signal was responsive to the amount of probe II, which was indirect proportional to the combined thrombin. The ECL intensity of the biosensor increased with the increase of thrombin concentration in the range of 0–20 μg mL−1. In addition, the biosensor exhibited the excellent selectivity responses and good stability toward the target analyte.