A fluorescent aptasensor for potassium ion detection-based triple-helix molecular switch.

Here, a biosensor based on a quadruplex-forming aptamer for the determination of potassium ion (K(+)) is presented. The aptamer was used as a molecular recognition element; it was adjacent to two arm fragments and a dual-labeled oligonucleotide serving as a signal transduction probe (STP) that is complementary of the arm fragment sequence. In the presence of K(+), the aptamer was displaced from the STP, which was accompanied by decreased signal. The quenching percentage of fluorescence intensity was proportional to the concentration of K(+) in the range of 0.05 to 1.4mM. A detection limit of 0.014 mM was achieved. Furthermore, other metal ions, such as Na(+), Li(+), NH4(+), Mg(2+), and Ca(2+), caused no notable interference on the detection of K(+).