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 alpha-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 alpha-thrombin binding aptamer (TBA). Thus, the aptasensor could be used for detection of ATP and alpha-thrombin both. The detection limit of ATP was 1 x 10(-8) M, and its detection range could extend up to 10(-4) M, whereas the detection limit of alpha-thrombin was 1 x 10(-11) M, and its detection range was from 1 x 10(-11) to 1 x 10(-7) M. Meanwhile, after detecting alpha-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 alpha-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.