Statistical differences were obtained using the analysis of variance, and the Dunnett’s and Turkey’s tests (SPSS v. 12 program). Results Cytotoxic activity of colloidal silver on MCF-7 human breast cancer cells As observed in Figure 1, colloidal silver induced dose-dependent cytotoxic effect on MCF-7 breast cancer cells; the median

lethal dose was (LD50) 3.5 ng/mL and the lethal dose (LD100) was 14 ng/mL (*P < 0.05). In contrast, colloidal silver treatment did not affect PBMC viability (Figure 1). These LD50 and LD100 were used in further experiments. Figure 1 Cell viability selleck kinase inhibitor of MCF-7 cell line and PBMC treated with colloidal silver. Cells (5 × 103 cells/well) were plated on 96 flat-bottom well plates, and incubated 24 h at 37°C in 5% CO2 atmosphere. After incubation, culture medium was removed, and colloidal silver diluted in the same medium was added at concentrations ranging from 1.75 to 17.5 ng/mL. The plates were then incubated for 5 h at 37°C, and 5% CO2 atmosphere. Thereafter, the supernatant was removed and

cells were washed twice with DMEM/F-12 medium. Cell viability was determined by the trypan blue exclusion method, and cytotoxicity was expressed as the concentration of 50% (LD50) and 100% (LD100) cell growth inhibition. The experiments were performed in triplicates; data shown represent mean + SD of three independent experiments. *P < 0.05 as compared with APR-246 concentration untreated cells. Colloidal silver induced apoptosis in MCF-7 breast cancer cells The colloidal silver induced the mechanism of cell death through apoptosis in MCF-7 human breast cancer cell line, determined by the detection

of mono-oligonucleosomes. The effects of LD50 and LD100 in control cells only caused non-significant cytotoxicity of 3.05% (P < 0.05), respectively (Figure 2). The TUNEL technique was also used to detect apoptosis. Labeling of DNA strand breaks in situ by TUNEL demonstrated positive cells that were localized in MCF-7 cells treated with LD50 and LD100 and control, with increased cell apoptosis in the LD50 and LD100 (Figure 3). Figure 2 Apoptosis mediated by colloidal silver on MCF-7 cell line. MCF-7 cells were treated with increasing concentrations of colloidal silver (1.75 to 17.5 ID-8 ng/mL) for 5 h. Thereafter, the levels of mono-oligo nucleosome fragments were quantified using the Cell Death Detection Kit. The experiments were performed in triplicates; data shown represent mean + SD of three independent experiments. *P < 0.05 as compared with untreated cells. Figure 3 MCF-7 cells stained by the TUNEL technique, counterstained with methyl green. (a) MCF-7 control, showing few brown staining of cells (arrows). (b) MCF-7 treated with colloidal silver LD50 (c) and LD100 showing abundant brown staining of cells (arrows). Original magnifications, a, b, and c : 40 ×.