Intracellular labeling of live cells via transient membrane permeabilization for fluorescence and super resolution microscopy

Fluorescence imaging of intracellular proteins is often achieved by using transfection-induced expression of fluorescent protein. This can potentially impose artifacts such as loss of function or over-expression of target proteins. Direct labeling of the intracellular protein is an alternative to transfection, but is largely limited by permeability of the fluorescent probes. Here, we have developed a high-throughput technique for labeling intracellular proteins of living cells. The technique makes use of Streptolysin O (SLO), a bacterial enzyme that permeabilizes cells to DNA, RNA, proteins. We show that SLO can be used to deliver a variety of fluorescent probes; ranging from organic dyes (