Cellular responses in titanium dioxide nanoparticle cytotoxicity studies: parts of the map waiting to be composed

With the infiltration of nanotechnology into our daily life, exposure to Titanium Dioxide Nanoparticles (TNPs) has become inevitable. Many forms of exposures are capable of affecting the human health. Current research in the Titanium dioxide nanoparticle pathology field reveals that TNP is capable of inducing severe oxidative stress to in vivo and in vitro cells, which predominantly result in cellular apoptosis. This article summarizes the main pathways of TNP induced apoptosis and compares it with cigarette-smoke-induced senescence, in an attempt to identify the similarities and acknowledge knowledge gaps to question the integrity of the TNP cytotoxicity studies conducted. The viable cells in the studies reviewed are not defined, and may provide a direction for future TNP toxicology studies.