Cellular Effects of Ultraviolet-Radiated Reduced-Titanium Dioxide Nanoparticles on Human Hypopharyngeal...

The cellular effects of ultraviolet (UV)-radiated reduced-titanium dioxide (TiO₂) nanoparticles were investigated on human hypopharyngeal adenocarcinoma cells (FaDu). In 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, the viability of FaDu cells exposed to UV (254 nm) for 10 minutes, in the presence of reduced-TiO₂ nanoparticles in rutile, was dose- and time-dependently decreased. The UV-radiated reduced-TiO₂ suppressed the cell proliferation by inhibiting the expression of cell cycle kinase, cyclin dependent kinase 2 (Cdk2), and its functional regulators Cyclin E and Cyclin B1 as well as proliferation-regulating proteins of p85 regulatory sub-unit of phosphoinositide3-kinases (PI3K p85), phosphorylated protein kinase B (p-AKT/p-PKB) and phosphorylated mammalian target of rapamycin (p-mTOR). In addition, the mitochondria disintegration and deoxyribonucleic acid (DNA) damage were confirmed by detecting the accumulated Bax in cytoplasm, phosphorylated-H2A histone family member X (γ-H2AX) in chromosomes and phosphorylated checkpoint 2 (p-Chk2). Our results support that UV-activated reduced-TiO₂ in rutile sensitized UV-induced proliferation suppression of FaDu cancer cells by the enhanced photocat-alytic activity.