Application of DNA aptamers as sensing layers for electrochemical detection of potassium ions

Determination of potassium level in organism is of special importance due to its vital role in the maintenance of physiological activities in organism. Herein, an electrochemical sensor for K+ ions was developed with recognition layer based on DNA aptamers. The elaborated assay was formed by tethering of thiolated aptamer probes to gold disk electrode via Au-S bond. Potassium concentration was determined with the use of voltammetric techniques by comparison of current change of redox indicators-methylene blue (MB), AQMS and Na4Fe(CN)6. The studies revealed that among aptamer sequences, which were previously shown to bind with potassium ions, 15-mer thrombin binding aptamer (TBA) exhibited highest affinity towards potassium with Kd = 1.13 μmol L−1 when used as a sensing layer. The aptasensor demonstrated linear response within the range from 10−8 to 10−5 mol L−1 with a LOD of 2.31 × 10−9 mol L−1 and good selectivity towards K+ ions with the use of MB electroactive marker.