Multifunctional label-free electrochemical biosensor based on an integrated aptamer

Aptamers, which are in vitro selected functional oligonucleotides, have been employed to design novel biosensors (i.e., aptasensors) due to their inherent selectivity, affinity, and their multifarious advantages over traditional recognition elements. In this work, we reported a multifunctional reusable label-free electrochemical biosensor based on an integrated aptamer for parallel detection of adenosine triphosphate (ATP) and α-thrombin, by using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). A Au electrode as the sensing surface was modified with a part DNA duplex which contained a 5′-thiolated partly complementary strand (PCS) and a mixed aptamer (MBA). The unimolecular MBA contained small-molecule ATP binding aptamer (ABA) and also protein α-thrombin binding aptamer (TBA). Thus, the aptasensor could be used for detection of ATP and α-thrombin both. The detection limit of ATP was 1 × 10^-8 M, and its detection range could extend up to 10^-4 M, whereas the detection limit of α-thrombin was 1 × 10^-11 M, and its detection range was from 1 × 10^-11 to 1 × 10^-7 M. Meanwhile, after detecting α-thrombin, the sensing interface could be used for ATP recognition as well. The aptasensor regeneration could be realized by rehybridizing of the MBA strand with the partly complementary strand immobilized on the Au surface after ATP detection or by treating with a large amount of ATP and then rehybridizing the MBA strand with the partly complementary strand immobilized on the Au surface after α-thrombin detection. The aptasensor fabricated exhibited several advantages such as label-free detection, high sensitivity, regeneration, and multifunctional recognition. It also showed the detectability in biological fluid. Therein it held promising potential for integration of the sensing ability such as the simultaneous detection for multianalysis in the future.