DEVELOPMENT OF A FLUORESCENT OPTICAL POTASSIUM-SELECTIVE ION SENSOR WITH RATIOMETRIC RESPONSE FOR INTRACELLULAR APPLICATIONS

A small, fluorescent fiber-optic potassium sensor is described with a working range which covers both intracellular cytosolic and blood leve ls of potassium at the respective physiological pH values. The highly potassium-selective ionophore, BME-44, is retained in a plasticized po ly(vinyl chloride) (PVC) Nm which is placed on the end of an optical f iber. Three optode configurations are given, employing different lipop hilic, fluorescent pH chromoionophores (Nile Blue derivatives), demons trating the ability to improve the detection limit and tune the dynami c range to the desired region of interest. These optodes also have exc ellent selectivity over sodium, calcium and magnesium Use of fluoresce nce (in contrast to absorbance) provides a means to reduce the sensor size dramatically while retaining the same signal-to-noise ratio. Thes e optodes measure the sample's potassium activity (rather than concent ration) provided that the sample's pH is measured simultaneously by an other sensor, such as a glass pH electrode.