SBFI is a membrane-permeant fluorescent Na+ indicator dye, excited at 340 nm with emission collected at 450 nm [1]. It selectively indicates Na+ over K+ with Kd values of 20 mM and 120 mM for these ions, respectively [2].

The preparation method for SBFI dye of each sample is as follows: [1] 1. Dissolve an appropriate amount of dye powder in 3 mL of dimethyl sulfoxide. 2. Stir the five solutions for 5 minutes. 3. Expose each sample to ultraviolet light using a Leitz Orthoplan microscope and record the fluorescence levels. 4. Obtain a total of ten readings for each solution, stirring between readings. 5. Plot the maximum, minimum, and median values based on dye concentration for each set of sample results. 6. The optimal fluorescence value with minimal variation in upper and lower limits was determined using 50 μg SBFI dye.