What are the alternatives to SBFI for measuring sodium levels in cells?

There are various alternatives to SBFI for measuring sodium levels in cells. Indicator dyes such as Sodium Green indicator, Asante Sodium Green, and CoroNa Green are effective alternatives to the conventional SBFI. 

1. Sodium Green indicators are excited at 488 nm, and can be used with flow cytometers as well as confocal laser-scanning microscopes. The crown ether has a unique size which permits it to selectively bind with Na+ ions. In comparison to SBFI, this indicator exhibits higher selectivity for Na+ than K+ (41 times greater), and has a greater fluorescence quantum yield (0.2 compared to 0.08 in SBFI) for Na+ solutions. 
2. Corona Green is a green fluorescent Na+ indicator which displays an increase in fluorescence intensity as it binds to Na+. It has an fluorescence excitation/emission ratio of 492/516 nm. It is smaller in size than Sodium Green, which makes it more effective in loading cells compared to the larger tetraacetate. 
3. Asante Sodium Green indicator is another Na+ indicator, with a fluorescence excitation/emission ratio of 517/540 nm. It is also able to be excited at a wavelength of 488 nm. This dye offers cytosolic fluorescence and signal stability as there is no dye loss or bleaching for longer than 1 hour at 37°C.

In addition to these alternatives, a sodium blood test can be carried out to measure the concentration of sodium levels in the blood. This is done intravenously with a needle. A urine test may also be used to measure sodium levels, however, this is a measure of the amount of sodium in urine. These tests are done to check if an individual is hydrated and to see if the body is functioning properly.