Fluorescein labeled phalloidin

Cell morphology and viability were routinely monitored with an Olympus CKX31 phase contrast microscope during the time course of treatment. To analyze the cytoskeleton structure, the cells were fixed with 3% paraformaldehyde, permeabilized with 0.1% Triton X-100 in PBS for 15 min at room temperature, and stained with 5 μg/ml fluorescein-labeled phalloidin (Sigma-Aldrich, St Louis, MO). Microfilaments were visualized under a Nikon fluorescence microscope (ECLIPSE 80i). The images were acquired with a digital camera mounted on the microscope. Cell viability was quantitatively determined by the number of viable cells after toluidine blue staining as we previously described (5 (link)). The absorbance at 630 nm of stained cells was measured with a microtiter plate reader. The values, which correlate with the number of viable cells, were used as an indirect measurement of cell proliferation or viability.