NBT (Nitro blue tetrazolium, chloride) is an oxidant and is widely used in conjunction with BCIP or BCIP derivatives to detect phosphatase activity. NBT is also a substrate for dehydrogenate and other oxidizes. Thus, it is often used to assess cell viability, proliferation and cytotoxicity, and is also frequently used in histochemistry studies. The colorless NBT is soluble in water, but forms a dark blue-colored, highly insoluble precipitate after being enzymatically reduced.
