Aptamer biosensor for label-free impedance spectroscopy detection of potassium ion based on DNA G-quadruplex conformation.

Abstract Herein, a label-free and highly sensitive electrochemical impedance spectroscopy (EIS) aptasensor for the detection of potassium ion (K + ) was developed based on a conformational change in which a K + -stabilized single stranded DNA (ssDNA) with G-rich sequence was used as the recognition element. In the measurement of K + ions, the change in interfacial electron transfer resistance ( R ct ) of the sensor using a redox couple of [Fe(CN) 6 ] 3−/4− as the probe was monitored. In the presence of K + , the G-rich DNA folded into the G-quadruplex structure, and then K + can bind to the G-quadruplex structure, leading to an increase in the R ct . The R ct increased with K + concentration, and the plot of R ct against the logarithm of K + concentration is linear over the range from 0.1 nM to 1 mM with a detection limit of 0.1 nM. Other metal ions, such as Ca 2+ , Mg 2+ , Na + , Li + , Al 3+ , Zn 2+ , Cu 2+ , and Ni 2+ caused no notable interference on the detection of K + . The scheme reported herein is applicable to the detection of other kinds of G-rich aptamer-binding chemicals and biomolecules.