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. 2013 Jun 11;8(6):e66084. doi: 10.1371/journal.pone.0066084

Figure 2. BR2 specifically penetrates cancer cell membranes in a concentration-dependent manner.

Figure 2

(A) Analysis of the cell-penetrating efficiency of each peptide in different cell types by flow cytometry. FITC-labeled Tat, BR1 and BR2 peptides (10 µM) were added to different cell types: HeLa, HCT116 and B16/F10 cancer cells and HaCat, BJ and NIH 3T3 normal cells. After 30 min of incubation at 37°C, the FITC-positive cells were counted by flow cytometry. Values represent the percentage of fluorescence-positive cells in the total cell population. (B) Quantitative assessment of cell penetration of each peptide by flow cytometry. HeLa cells were incubated with FITC-labeled peptides at concentrations of 1, 2, 5, or 10 µM for 30 min at 37°C. Afterwards the cells were washed with cold PBS and harvested and cellular fluorescence was analyzed by flow cytometry. Control cells did not receive peptide treatment. Prior to analysis, extracellular fluorescence of surface bound peptides was removed by a trypsin treatment (1 mg/ml for 10 min).