What is the dye concentration for calcium indicators?

The optimal concentration of calcium indicators can vary depending on factors such as the specific dye, experimental conditions, and cell types. For each member of the Fluo series, as the concentration of intracellular calcium increases, the dye undergoes a significant boost in fluorescence, often exceeding a 100-fold increase. Each specific Fluo dye within the series has a unique affinity for intracellular calcium, allowing researchers to choose the one that best matches the range of calcium concentrations they wish to study. As a general guideline, calcium indicator concentrations often fall within the range of 1 to 20 micromolar (µM). In one study, fluorescent sensors with reduced affinity were designed to visualize calcium levels within cellular organelles, particularly in cases where free calcium concentrations can be in the range of several hundred micromolar.