Teng, K.W. et al. eLife 5, e20378 (2016).

Fluorescent dyes often have properties desirable for microscopy, including high brightness and photostability. However, many are not cell permeable and are thus challenging to use in live-cell imaging. Teng et al. sought to bypass cell permeability and develop a general strategy for labeling proteins in mammalian cells with exogenous fluorophores. To do so, they used a pore-forming enzyme called Streptolysin O to poke holes into mammalian cells, allowing various reagents to enter. The holes were then repaired by the cells, which remained largely viable. Using this strategy, the team delivered a range of probes, including fluorescently labeled antibodies, into cells. They were also able to deliver oxygen scavengers into cells for prolonged imaging, as well as glutathione, a reagent that enables fluorophore blinking for single-molecule localization-based super-resolution imaging.