A label-free electrochemiluminescence aptasensor for thrombin detection based on host-guest recognition between tris(bipyridine)ruthenium(II)-β-cyclodextrin and aptamer

An ultrasensitive label-free electrochemiluminescence (ECL) aptasensor for the detection of thrombin was developed based on the specific recognition between tris(bipyridine)ruthenium(II)-β-cyclodextrin (tris(bpyRu)-β-CD) and the anti-thrombin aptamer (aptamer). The NH₂-aptamer was first immobilized on the activated glassy carbon electrode (GCE) by coupling interaction. By use of the specific recognition between tris(bpyRu)-β-CD and aptamer, tris(bpyRu)-β-CD was then attached on the surface of GCE. Resulting from the outstanding photoactive properties of tris(bpyRu)-β-CD, the fabricated GCE performed strong ECL signal with the coreactant of 2-(dibutylamino)ethanol (DBAE). However, in the presence of thrombin, aptamer-thrombin bioaffinity complexes were formed, which restricted the recognition activities between aptamer and tris(bpyRu)-β-CD. Thus, fewer tris(bpyRu)-β-CD could be attached on the surface of GCE and led to an obvious decrease of ECL signal. Fortunately, the difference of ECL intensity before and after combination with thrombin was logarithmically linear with the concentration of thrombin in a wide range of 10nM-1pM. Meantime, a detection limit of 0.1pM without any other signal labeling or amplifying procedures indicated that the biosensor performed excellent sensitivity, operability and simplicity.