Fig. 4.

The delivery of phalloidin into cells by pHLIP. (a) Fluorescence images of HeLa cells incubated (for 1 h) with a pHLIP–S–S–Ph–TRITC cleavable construct (2 μM) at pH 7.4 (Left) and 6.5 (Right) are shown. The fluorescence was extremely weak after pH 7.4 incubation and localized to the plasma membrane. Strong fluorescence of actin filaments was observed after pH 6.5 incubation. (b) Images of HeLa (Left), breast JC (Center), and prostate TRAMP-C1 (Right) cancer cells with fluorescent actin filaments are shown. Cells were incubated for 1 h with the cleavable pHLIP–S–S–Ph–TRITC (0.5–1 μM) at pH 6.5 followed by washing with PBS at pH 7.4.