Titanium dioxide nanoparticles: Protein adsorption and cellular interactions
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Titanium dioxide nanoparticles are used in many applications from photocatalysis to pigmentation. Their presence in commercial products such as paints, sunscreens, cosmetics, and food motivates interest in understanding how these nanoparticles interact with a cellular environment. We note that oxidative stress occurs after a 24 hour incubation with low, nontoxic concentrations of titanium dioxide nanoparticles. This intracellular change, characterized by the alteration in gene expression of the peroxiredoxin family of anti-oxidant enzymes, is further examined in relation to the reactivity of the nanoparticle surface and to the adsorbed serum proteins, or the protein corona. Both industrial and food grade titanium dioxide nanoparticles generated hydroxyl radicals and superoxides at the particle surface in the absence of light. These reactive oxygen species further oxidized serum proteins and the plasma membrane. It is shown that an oxidized protein corona leads to oxidative stress. These findings confirm titanium dioxide nanoparticles induce various molecular changes on multiple levels extra- and intracellularly.