Background:

IQ-R is a novel hypoxia-sensitive fluorescent probe, consisting of an indolequinone unit and a rhodol fluorophore.Target:IQ-R has good solubility in water and longer wavelength for absorption and emission, which are favorable for cellular bioimaging. While the fluorescence of rhodol in the IQ-R conjugate is quenched by the function of intramolecular indolequinone unit, it is restored under hypoxic conditions through the enzymatic one-electron reduction of IQ-R by NADPH: cytochrome P450 reductase to release the nonconjugated free rhodol. When administered to A549 cells, IQ-R is activated and reduced by endogenous reductase preferentially under hypoxic conditions, thereby visualizing hypoxic cancer cells by robust fluorescence.

[1]. Hirokazu Komatsu,et al. Indolequinone-rhodol conjugate as a fluorescent probe for hypoxic cells: enzymatic activation and fluorescence properties. Med. Chem. Commun., 2010,1, 50-53