Cytotoxic effect of green synthesized silver nanoparticles in MCF7 and MDA-MB-231 human breast cancer cells in vitro

With the incessant rise in the cancer burden worldwide it is a dire need to develop anticancer agents that will offer negligible or no side effects and at the same time will be economically feasible. In this study, we utilized the principle of green chemistry where tyrosine and chitosan were used as reducer and stabilizer respectively to synthesize biocompatible silver nanoparticles. They were characterized by ultraviolet-visible spectroscopy, transmission electron microscopy and dynamic light scattering technique and found to be spherical with average diameter of 13-22 nm. Their toxicity was evaluated in MCF7 and MDA-MB-231 human breast cancer cell lines. MTT assay revealed excellent cytotoxic effect with IC50 values as low as 6.4 and 6.56 ppb respectively after 48 h of treatment. Intriguingly, they showed minimum toxicity in normal human peripheral blood lymphocytes at these effective concentrations. Cytomorphological alteration, ROS generation (DCFDA analysis) and nuclear fragmentation (Hoechst staining) were pronounced in both cancer cell lines following treatment. These nanoparticles also promoted expression and nuclear translocation of Nrf2 as an antioxidant response which was revealed by Western blot and immunofluorescence studies respectively. 'Apoptosis assay' confirmed the presence of apoptosis and 'Caspase-8 activity assay' revealed absence of the extrinsic apoptosis pathway. Western blot data (upregulation of p21, Bax/Bcl2 ratio, Caspase-9, Caspase-3 and cleaved PARP1) established the occurrence of intrinsic apoptosis pathway following cell cycle arrest. To conclude, the green synthesized silver nanoparticles are cytotoxic to cancer cells and can be considered as effective and safe cytotoxic agents in breast cancer therapeutics.