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

An electrochemical biosensor for potassium has been developed combining specific potassium-aptamer binding and RecJ(f) 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 RecJ(f) exonuclease, releasing K+ which can bind to another DNA probe on the electrode. After cycles of RecJ(f) 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.