Preparation of Label-free Thrombin Aptasensor Based on Pd-Au Nanoparticles

Pd nanoparticles (Pd NPs) were electrodeposited on the glassy carbon electrode (GCE). Then, Pd NPs/GCE was further inserted into H2SO4 solution to polarize for 5 min to absorb a certain amount of active hydrogen. Then, the electrode was quickly inserted to HAuCl4 solution for 15 min. AuNPs were deposited spontaneously on the surface of Pd NPs due to the reduction of active hydrogen. As a result, Pd-AuNPs were modified on the surface of GCE. Next, aptamer I of thrombin was immobilized on Pd-Au nanoparticles. In the presence of thrombin, it bound with the aptamer immobilized on Pd-Au nanoparticles and thus the formed complex obstructed the catalysis of Pd-Au nanoparticles to H2O2. Hence, the reduction current of H2O2 decreased with the increase of thrombin concentration. The aptamer sensor had a good linear relationship with the concentration of thrombin in the range of 2. 98-297 nmol/L with a detection limit of 0. 98 nmol/L.