Cells were rinsed twice with phosphate buffered saline (PBS) and permeabilized with 0.1 % Triton in PBS for ten minutes. Actin filaments were stained with phalloidin fluorescein isothiocyanate (FITC) (Sigma) for thirty minutes at room temperature. After washing twice with PBS, nuclei were counterstained with 4′,6-diamidino-2-phenylindole (DAPI). Coverslips were mounted with a glycerol/water solution (1/1, v/v). Observations were conducted under a confocal microscopy (Leica TCS SP5 imaging system) equipped with an argon ion and a 561 nm DPSS laser. Cells were imaged using a HCX PL APO 63×/1.4 NA oil immersion objective. NDs were excited by 561 nm laser, while the emission was collected in the 570-760 nm spectral range. Phalloidin was imaged using 458 nm laser and the emission collected in the 498-560 nm range. DAPI was imaged using 405 nm laser and the emission was collected in the 415-498 nm range. Image analysis was performed using ImageJ software.