Nanomaterial-amplified “signal off/on” electrogenerated chemiluminescence aptasensors for the detection of thrombin

Two electrogenerated chemiluminescence (ECL) aptasensors for the detection of thrombin were developed using the thrombin binding aptamer (TBA) taken as a molecular recognition element and nanomaterial as a carrier of the ECL capture/signal probe. In the “signal off” aptasensor, the thiolated capture probe (ss-DNA, 12-mer) was self-assembled on the gold nanoparticles (GNPs) which were self-assembled on the surface of gold electrode, and hybridized with six-base segment of the ss-DNA sequence (Tgt-aptamer, 21-mer) containing TBA-I (ss-DNA, 15-mer) tagged with ruthenium complex, producing a high ECL intensity. Introduction of the analyte thrombin triggered the dissociation of the Tgt-aptamer tagged with ruthenium complex from the aptasensors, led to significantly decrease in ECL intensity. The decreased ECL intensity was in proportion to the concentration of thrombin in a range from 2.7 × 10−12 to 2.7 × 10−9 M with a detection limit of 8 × 10−13 M. In the “signal on” aptasensor, the thiolated TBA-I was self-assembled on the gold electrode for capturing thrombin onto the electrode and then the TBA-II (ss-DNA, 29-mer) labeled with single-walled carbon-nanotubes (SWNT)-ECL tag was bound with epitope of thrombin, producing a high ECL intensity. The increased ECL intensity was linearly with the concentration of thrombin from 1.0 × 10−14 M to 1.0 × 10−11 M with a detection limit of 3 × 10−15 M. The present work demonstrates that using nanomaterial as a carrier for capture probe and signal probe is a promising way to amplify the ECL signal and to improve the sensitivity of the aptasensors.