titanium nanoparticles (TiO2 NPs) are small spherical or faceted high surface area metal particles. These spherical particles are typically 10 – 80 nanometers in diameter with specific surface areas in the range of 15 – 20 m2/g, while faceted particles can be much larger.

Nanoparticles are highly reactive and can cause problems in the environment, as well as in human health. Hence, it is essential that they are properly assessed for human or environmental health effects and adequately regulated.

TiO2 NPs are used in a variety of applications. Some of these include:

Antibacterial activity against bacteria S. aureus and E. coli by leaf extracts of Cynodon dactylon and Diospyros ebenum, respectively [85].

Green synthesis of titanium oxide NPs using phenols and anthraquinones from Morinda citrifolia leaves hydrothermally; exhibited antibacterial activity against S. aureus, Bacillus subtilis and fungi Candida albicans and A. niger, respectively.

Photo catalytic removal of chlorhexidine digluconate, a common antiseptic in the pharmaceutical industry, by an intimate contacted two-dimensional/zero-dimensional composite of bismuth oxychloride and titanium dioxide nanoparticles utilizing ultraviolet light and pH 10.5. The photocatalytic activity was remarkably enhanced by the well-dispersed copper ions.

Moreover, a chiro-plasmonic metamaterial with refractory titanium nitride core-shell nanohelices was used to enhance the performance of a wearable sensor for the determination of halides.

Although 3D models have been commonly used for the safety assessment of chemicals, to date no information is available regarding the toxicological evaluation of TiO2 NPs in osteoblasts-like spheroids. Therefore, our study aims to answer the following question: Can the toxicity of TiO2 NPs be assessed in a 3D skin model?