In vitro cytotoxicity and cellular uptake were conducted in the human breast cancer (MCF-7), TNBC (MDA-MB-231), and embryonic kidney (HEK293) cells, while the effect of anti-TNF-α siRNA nanocomplexes on biological processes, such as oxidative stress, apoptosis, and cell cycle distribution, was investigated using flow cytometry. The gene discussed is TNF; the disease is breast cancer.