ATP-Red 1 is a multisite-binding switchable fluorescent probe, and can selectively and rapidly responds to intracellular concentrations of ATP in living cells. The maximum absorption and emission wavelength of are 570/566 nm and 590/585 nm. ATP-Red 1 has good membrane permeability, and in the presence of 5?mM ATP, the fluorescence intensity of ATP-Red?1 increases 5.6-fold. ATP-Red?1 (2.5?μM, 20?min) shows much weaker fluorescence after KCN-induced inhibition of OXPHOS, which results in reduced mitochondrial ATP levels in OSCC cells.