Simple and sensitive fluorescence sensor for detection of potassium ion in the presence of high concentration of sodium ion using berberine-G-quadruplex complex as sensing element

In this work, a novel potassium ion (K+) sensor is presented using berberine-G-quadruplex complex as a fluorescent probe. This sensor is based on the K+that can induce the G-rich DNA to form G-quadruplex conformation. The G-quadruplex can bind berberine to form berberine-G-quadruplex complex, resulting in remarkable enhancement of fluorescence emission of the berberine-G-quadruplex system. In the presence of 800 mM sodium ion (Na+), the fluorescence of the berberine-G-quadruplex complex increased linearly with increasing K+ concentration in the range of 0.005-1.0 mM. The turn-on fluorescent assay is simple, inexpensive, and highly sensitive. We observed that Na+ in 10,000-fold molar excess does not interfere. The molecular mechanisms which produce enhanced fluorescence of berberine were discussed.