Reversible Off–On Fluorescence Probe for Hypoxia
and Imaging of Hypoxia–Normoxia Cycles in Live Cells
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Abstract
We
report a fully reversible off–on fluorescence probe for
hypoxia. The design employs QSY-21 as a Förster resonance energy
transfer (FRET) acceptor and cyanine dye Cy5 as a FRET donor, based
on our finding that QSY-21 undergoes one-electron bioreduction to
the radical under hypoxia, with an absorbance decrease at 660 nm.
At that point, FRET can no longer occur, and the dye becomes strongly
fluorescent. Upon recovery of normoxia, the radical is immediately
reoxidized to QSY-21, with loss of fluorescence due to restoration
of FRET. We show that this probe, RHyCy5, can monitor repeated hypoxia–normoxia
cycles in live cells