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A sensitive electrochemical biosensor for detection of thrombin based on target protein-induced strand displacement is pre- sented. For this proposed biosensor, dsDNA which was prepared by the hybridization reaction of the immobilized probe ssDNA (IP) con- taining thiol group and thrombin aptamer base sequence was initially immobilized on the Au electrode by self-assemble via Au-S bind, and a DNA labeled with PdS nanoparticles (DP-PdS) was used as a detection probe. When the so prepared dsDNA modified Au electrode was immersed into a solution containing target protein and DP-PdS, the aptamer in the dsDNA give priority to to form G-quarter structure with the present target protein and the dsDNA sequence was released one single strand and returned to IP strand which consequently hybrid- ized with DP-PdS. After dissolving the captured PdS particles from the electrode, a mercury-film electrode was used for electrochemical detection of these Pd2+ ions which offered sensitive electrochemical signal transduction. The peak current of Pd2+ ions had a good linear relationship with the thrombin concentration in the range of 7.3×10−8–7.3×10-11 mol/L and the detection limit was 2.3×10-11 mol/L of thrombin. The detection was also specific for thrombin without being affected by the coexistence of other proteins, such as BSA and ly- sozyme.
Electrochemical biosensor, Displacement, DNA hybridization, PdS nanoparticles, Thrombin
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