An aptasensor for detection of potassium ions based on RecJ f exonuclease mediated signal amplification

An electrochemical biosensor for potassium has been developed combining specific potassium-aptamer binding and RecJf exonuclease mediated signal amplification. Generally, the DNA probe with a stem-loop structure containing an anti-K(+) aptamer sequence is designed and modified on a gold electrode. K(+) can specifically bind to the aptamer and a G-quadruplex structure forms, which breaks the original stem-loop structure. The induced single-stranded 5' end can be further digested by RecJf exonuclease, releasing K(+) which can bind to another DNA probe on the electrode. After cycles of RecJf exonuclease cleavage initiated by K(+), the electrochemical signal intensity is significantly decreased, and can be used to determine the concentration of K(+). This aptasensor shows high sensitivity, selectivity as well as excellent stability and accuracy, which provides possibilities for further applications of K(+) assay in clinical diagnosis.