Trypan UltraBlue™ is similar to Trypan Blue in cell permeability. It is not permeable to live cells. Compared to Trypan Blue, Trypan UltraBlue is less toxic to cells, in particular, having minimal effect on cell surface receptors. Our Trypan UltraBlue™ sodium salt is highly purified. Our Trypan UltraBlue™ can also be used to prevent florescent dyes (such as FDA, rhodamine 123, JC-1, TMRE, TMRM, Indo-1 AM, Fura-2 AM, calcein AM, Fluo-3 AM, Fluo-4 AM, Quest Fluo-8™ AM and Rhod-4™ AM) from leaking out of cells. It might inhibit the activities of drug-efflux pumps since it contains a probenecid-like moiety as shown below. Compared to probenecid, it is neutral, highly soluble in water, and convenient to use. Its cellular mechanism is still under investigation. Our Trypan UltraBlue™ is highly purified, and can be used up to 0.5 mM with minimal cell cytotoxicity. Our recommended concentration is 0.25 mM.