Thrombin aptamer electrochemical aptasensor development

As an example of application of electrochemical aptasensor to medical diagnosis. Sun et al. developed a label-free electrochemical aptasensor for thrombin detection in whole blood. For the fabrication of this aptamers, self-assembled multilayers of carboxymethyl-polyethylene glycol-carboxymethyl (CM-PEG-CM) and thrombinbinding aptamer (TBA) were used. The thrombin molecules in the medium bound onto the TBA which leads to current decrease. This current decrease was monitored by differential pulse voltammetry. A linear range of 1 pM to 160nM was obtained for thrombin with LOD value of 1.56 x (Sun et al., 2013). 

Aptamer-based biosensors, also called aptasensor have gain a wide interest in the last years due to the advantages of aptamers compared to antibodies. Similar to antibodies, a variety of immobilization methods is available to bind aptamers to the sensor element. Aptasensors can be coupled to an electrochemical, optical or mass-sensitive transducer [13]. One of the successful examples for aptasensor was the detection of thrombin which was widely investigated [14]. Xiao et al. [15] have made an interesting development a redox compound (methylene blue) was inserted into the thrombin aptamer. When the target bound to the aptamer, the induced conformation change inhibited the electron transfer from the methylene blue to the electrode. This change could be detected amperometrically. 

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