Colorimetric detection of potassium ions using aptamer-functionalized gold nanoparticles.

Abstract Herein, a simple and novel colorimetric method for detection of potassium ions (K + ) was developed. The colorimetric experiments revealed that upon the addition of K + , the conformation of anti-K + aptamer in solution changed from random coil structure to compact rigid G-quadruplex one. This compact rigid G-quadruplex structure could not protect AuNPs against K + -induced aggregation, and thus the visible color change from wine-red to blue-purple could be observed by the naked eye. The linear range of the colorimetric aptasensor covered a large variation of K + concentration from 5 nM to 1 μM and the detection limit of 5 nM was obtained. Moreover, this assay was able to detect K + with high selectivity and had great potential applications.