LABEL FREE DETERMINATION OF POTASSIUM IONS USING CRYSTAL VIOLET AND THROMBIN-BINDING APTAMER

A label-free method for sensitive determination of potassium ions was developed. The most commonly studied thrombin-binding aptamer was used as the molecular probe and crystal violet was chosen as a fluorescence signal reporter. The fluorescence of crystal violet was significantly enhanced when the crystal violet solution was mixed with the single-stranded thrombin-binding aptamer. However, in the presence of potassium ions, due to the formation of potassium induced G-quadruplex structures, the fluorescence decreased. Potassium ions were determined using the change in fluorescence. The conformational transformation was investigated by circular dichroism, and interferences caused by sodium ions were studied. This label-free method offers a simple procedure that induces minimum effects on the G-quadruplex formation. Under the optimized conditions, the method exhibited a linear range from 30-420 mu M for potassium ions with a detection limit of 6 mu M.