Abstract: In this paper, a signal amplified electrochemical biosensor for thrombin based on the enrichment of the gold nanoparticles through the hybridization with the complememtary oligonucleotide was presented. Thrombin, as a typical protein model, has two combination sites with aptamers. In the experiment, aptamer Ⅰ was immobilized on magnetic nanoparticles for capturing thrombin, and aptamer Ⅱ was labeled with gold nanoparticle to offer an excellent electrochemical signal transduction. Through the specific recognition for thrombin, a sandwich format of magnetic nanoparticle/thrombin/gold nanoparticle was fabricated. And the signal amplification was further implemented by the enrichment of gold nanoparticles through the hybridization with the gold labeled complementary oligonucleotide，the resulting hybridization is capable of realizing more gold nanoparticle markers attaching to each target protein. A significant enhancement of the sensitivity was obtained for the detection of thrombin with the signal amplification. This new strategy allows the detection limit of the target protein down to 4.52×10^-15 mol/L. The relative standard deviation of eight replicate determinations of 7.47×10^-14 mol/L thrombin was 3.0%. The presence of other proteins such as BSA and lysozyme did not affect the detection of thrombin, which indicates that a high specificity of thrombin detection can be achieved.

Key words: Signal amplification, Nucleic acid aptamer, Thrombin, Gold nanoparticle, Electrochemical biosensor