Lysosome-targeting turn-on red/NIR BODIPY probes for imaging hypoxic cells

A small series of fluorescent lysosome-targeting probes based on the BODIPY fluorophore and containing morpholine and nitro groups were rationally designed. These probes emitted light from green to NIR wavelengths, and provided specificity for imaging the lysosomes of hypoxic cells. The electron-withdrawing nitrophenyl group at the meso position was found to lead to highly efficient nonradiative decay of the S1 state, and hence a recovery of fluorescence when reduction of the nitro group occurred under hypoxic conditions.