Electrochemical Aptasensor

Aptasensors appear as promising tools, based on aptamers that are very small in size compared to other biorecognition molecules like antibodies or enzymes. Several aptasensors for the detection of various targets ranging from small ion molecules to large proteins have been reported, using optical transduction, mass-sensitive or electrochemical detection. Among them, electrochemical aptasensors have been the most recently reported. Two main detection approaches have been used for electrochemical aptasensors:

1. The use of labels such as metal nanoparticles (NPs), enzymes, or redox compounds.
2. Noncovalently or covalently bound to aptamers, or aptamer label-free detection systems.

Electrochemical Aptasensor

The direct aptamer assay formats are concerned with the molecular recognition of the target using the cognate aptamer immobilized onto the sensing interface. The biosensing assays could be improved by using other different configurations such as sandwich-type, displacement-type and folding-based electrochemical aptasensors.

Sandwich-Type Electrochemical Aptasensor

The sandwich-type construct involves antibody-aptamer sandwich sensing layers. The antibody is used as a capture element and aptamer as a reporter probe or vice versa. The signaling portion is usually conjugated with a label which can be detected using electrochemical techniques. This format offers higher selectivity as compared to single-receptor approaches, due to the involvement of a pair of receptors-the capture and reporter.

Fig.1 Formation of sandwich-types structures of aptasensing assay. (Radi, 2021)

Displacement-Type Electrochemical Aptasensor

In this assay format, the authentic target molecules compete with labeled target molecules for specific binding sites on the sensor surface.

Fig.2 Displacement-type electrochemical aptasensor. (Radi, 2021)

Folding-Based Electrochemical Aptasensor

This assay format is based on the binding of electrode-bound DNA probes to induce folding. Electrochemical nucleic acid sensors using target-sensitive DNA structures with appropriate redox markers can monitor aptamer conformational changes by measuring electrochemical signals.

Fig.3 Folding-based electrochemical aptasensor. (Radi, 2021)

As a fascinating biosensing field and due to progressive advancements, different electrochemical aptasensors detection strategies have been proposed and applied. Nowadays, electrochemical aptasensors have been widely used for the detection of cardiac biomarkers, nerve disease biomarkers, infectious disease biomarkers, cancers, and so forth.

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Reference

1. Radi, A. E.; Abd-Ellatief, M. R. Electrochemical Aptasensors: Current Status and Future Perspectives. Diagnostics. 2021, 11(1): 104.

For Research Use Only.