The bioluminescent mechanic of the luciferin-luciferase reaction makes it a powerful tool for both in-vitro and in-vivo imaging. This substrate is water soluble, and when exposed to Mg2+ along with ATP and luciferase oxidizes in a reaction that creates light. This ability to produce light in the presence of ATP also makes Luciferin great for testing for the presence of life energy.
While luciferin and luciferase are used to target stem cells, cancer cells, and infectious diseases, anything can be imaged so long as it is modified to express luciferase. For more information on the Firefly Luciferin-luciferase reaction, see here.
The primary difference between potassium salt and sodium salt D-Luciferin forms is solubility. See technical data for more information.