A novel label-free fluorescent sensor for the detection of potassium ion based on DNAzyme

Abstract A novel label-free and sensitive fluorescent aptasensor for the detection of potassium ion (K + ) was developed based on the horseradish peroxidase–mimicking DNAzyme (HRP–DNAzyme). In this work, we selected a K + -stabilized single stranded DNA (ssDNA) with G-rich sequence as the recognition element. In the presence of K + , the G-rich DNA folded into the G-quadruplex structure, and then hemin can bind to the G-quadruplex structure as a co-factor and form HRP–DNAzyme. 3-( p -Hydroxyphenyl)-propanoic acid (HPPA) can be oxidized by H 2 O 2 into a fluorescent product in the presence of DNAzyme. The fluorescence intensity of the HPPA oxidative product increased with the K + concentration. Under the optimal conditions, the fluorescence intensity was linearly related to the logarithm of K + concentration in the range of 2.5 μM to 5 mM. Other metal ions, such as Na + , Li + , NH 4 + , Mg 2+ and Ca 2+ caused no notable interference on the detection of K + .