Colorimetric detection of potassium ions using aptamer-functionalized gold nanoparticles

•A simple and novel colorimetric method for detection of K+ was developed.•The aptasensor exhibited low detection limit and wide linear range to K+.•This method was able to detect K+ with high selectivity.•This colorimetric method exhibited excellent applicability.

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.

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