Morphology-dependent titanium dioxide nanoparticle-induced keratinocyte toxicity and exacerbation of allergic contact dermatitis.

Titanium dioxide (TiO₂) nanoparticles are commonly found in consumer products, such as sunscreens, and human dermal exposures are relatively high. Research suggests potential differences in the toxicity of anatase and rutile crystalline forms of TiO₂. Additionally, transition metal dopants are frequently used to enhance physicochemical properties of TiO₂, and the toxicity of these nanoparticles are not extensively studied. Therefore, this work examined the keratinocyte toxicity and in vivo skin allergy responses after treatment with 30 nm anatase, 30 nm rutile, or <100 nm Mn-doped TiO₂ nanoparticles. After a 24-hour exposure, there were no differences in keratinocyte cytotoxicity; however, Mn-doped TiO₂ nanoparticles induced significant in vitro ROS generation and in vivo skin swelling responses in a model of allergic contact dermatitis.