Electrochemical aptamer-based biosensors as potential tools for clinical diagnostics

Aptamers are single-stranded DNA and RNA sequences that belong to the group of functional nucleic acids, which exhibit both catalytic and receptor properties. Aptamers change their spatial conformation upon binding to a target analyte, and so far more than 200 sequences selective for large variety of molecules such as metal ions, organic dyes, proteins and bacteria cells have been identified. Aptamers can be applied in several fields including diagnostics, therapy and as the recognition layers for biosensors, which is one of the most promising areas. The utilization of aptamers as receptor elements in electrochemical assays requires not only the choice of an appropriate immobilization method with respect to the detected target, but also experimental conditions including the manner of analytical signal generation. The latter issue might affect the efficiency of binding between the aptamer-modified surface and analyte, and consequently the sensitivity of target molecule quantification. Herein, a review of electrochemical aptasensors dedicated to the determination of target analytes crucial in clinical diagnostics developed during the past 10 years is presented. It contains a short characterization of aptamers and their application as sensing layers in electrochemical assays, which is followed by a description of the examples of the use of aptasensors.