Highly Selective Detection of K+ Based on a Dimerized G-Quadruplex DNAzyme.

Potassium ion (K+) plays a crucial role in biological systems, such as maintaining cellular processes and causing diseases. However, specifically, the detection of K+ is extremely challenging because of the coexistence of the chemically similar ion of Na+ under physiological conditions. In this work, a K+ specific biosensor is constructed on the basis of a dimerized G-quadruplex (GQ) DNA, which is promoted by K+, and the enzymatic activity of the resulting DNAzyme depends on the concentration of the K+. The K+ in a 1-200 mM concentration range can be selectively detected by visual color, UV-Vis absorbance or fluorescence even if the concentration of the accompanying Na+ is up to 140 mM at an ambient condition up to 45 °C. In addition, this system can also be used to selectively detect NH4+ in a 5-200 mM concentration range. This dimerized DNAzyme offers a new type of biosensor with a potential application in the biological system.