Mechanistic Insight into Size-Dependent Enhanced Cytotoxicity of Industrial Antibacterial Titanium Oxide Nanoparticles on Colon Cells Because of Reactive Oxygen Species Quenching and Neutral Lipid Alteration

This study evaluates the impact of industrially prepared TiO2 nanoparticles on the biological system by using an in vitro model of colon cancer cell lines (HCT116). Industrial synthesis of titanium oxide nanoparticles was mimicked on the lab scale by the high-energy ball milling method by milling bulk titanium oxide particles for 5, 10, and 15 h in an ambient environment. The physiochemical characterization by field emission scanning electron microscopy, dynamic light scattering, and UV-visible spectroscopy revealed alteration in the size and surface charge with respect to increase in the milling time. The size was found to be reduced to 82 +/- 14, 66 +/- 12, and 42 +/- 10 nm in 5, 10, and 15 h milled nano TiO2 from 105 +/- 12 nm of bulk TiO2, whereas the zeta potential increased along with the milling time in all biological media. Cytotoxicity and genotoxicity assays performed with HCT116 cell lines by MTT assay, oxidative stress, intracellular lipid analysis, apoptosis, and cell cycle estimation depicted cytotoxicity as a consequence of reactive oxygen species quenching and lipid accumulation, inducing significant apoptosis and genotoxic cytotoxicity. In silico analysis depicted the role of Sod1, Sod2, p53, and VLDR proteins-TiO2 hydrogen bond interaction having a key role in determining the cytotoxicity. The particles exhibited significant antibacterial activities against Escherichia coli and Salmonella typhimurium.