Electrochemical Aptasensors Based on Noncovalent Redox Species Label

A detection limit of 0.55 fM of thrombin was calculated. Authors attribute the significant improvement of the sensitivity of such aptasensors with respect to others present in literature to the use of a nanoelectrode, formed by immobilization of Au-NPs on the surface of a gold electrode, to the use of NPs as labels, and to the use of DPV technique for the detection of the dissolved Cd + in the solution. Moreover, the electrochemical aptasensor was successfully tested in some serum samples. 

7 Electrochemical Aptasensors Based on Noncovalent Redox Species Label 

These aptasensors are based on the use of a redox probe such as methylene blue (MB) that undergoes an oxidation and reduction due to the electron transfer from an electrode surface to a probe. These redox probes are noncovalently bound to aptamers and intercalate or interact with aptamers mainly by electrostatic interactions. For example, MB, positively charged, interacts with negatively charged proteins or other negatively charged analytes. When 

Another commonly used redox probe is Fe(CN) which has been coupled to different electrochemical techniques as summarized in Table 2.1. 

A very recent example of the use of this redox probe in an aptamer-based biosensor was published by Kim et al. [33]. An electrochemical biosensor for ox3d etracycline detection was developed using ssDNA aptamer immobilized on gold interdigitated array (IDA) electrode chip (Fig. 2.7). Cyclic voltammetry and square wave voltammetry were used to measure the current at the electrode chip 

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