Development of an electrochemical aptasensor for thrombin based on aptamer/Pd-AuNPs/HRP conjugates

Using Pd-Au nanoparticles functionalized with an aptamer and horseradish peroxidase (Ap/Pd-AuNPs/HRP), we developed a new electrochemical aptasensor for the detection of thrombin. The thiolated single-stranded DNA used as the capture probe was first self-assembled on a gold electrode. Then the Ap/Pd-AuNPs/HRP conjugates were attached to the electrode surface via the hybridization of the capture probe with thrombin aptamer. In the presence of thrombin, Ap/Pd-AuNPs/HRP conjugates dissociated from the electrode surface due to the formation of a tertiary target-aptamer complex, which reduced the amount of HRP and therefore resulted in the decrease of the electrochemical signal. According to this strategy, thrombin was detected within the range from 0.05 to 50 nM with a detection limit of 3 pMbased on S/N = 3. The proposed aptasensor had a good specificity, stability and reproducibility.