Electrochemical Aptasensors Based on a Sandwich Assay

Ikebukuro et al. [12] first reported an electrochemical aptasensor for the detection of thrombin based on a sandwich-based assay. Two different aptamers specific for thrombin were used the 29-mer thiolated aptamer and the 15-mer aptamer labeled with glucose dehydrogenase [GDH]. The thiolated aptamer was immobilized onto gold electrodes thrombin at different concentrations and then the enzyme-labeled aptamer was added to the aptamer-modified electrodes. The electric current generated by the addition of glucose was measured at 0.1 V vs. Ag/AgCl in a buffer containing 

Q Streptavidin-coated magnetic bead I 5 biotinylated aptamer 

1-methoxyphenazine methosulfate (m-PMS). Using this approach, 10 nM of thrombin was detected. 

The detection limit calculated using this approach was 0.02 nM of thrombin. A similar approach was reported by Degefa and coworkers [15] as well. 

---