Table 2.

Inclusion and exclusion criteria.

PECO	Inclusion	Exclusion
Population	In vitro study in 3D skin model	Clinical trials In vivo studies In vitro studies of monolayer culture
Exposure	Exposure of TiO2 NPs TiO2 must have nanometric size TiO2 suspensions in any crystalline phase or mixture	Average size in micrometric scale
Comparison	3D model without NPs exposure
Outcome	Effects generated by NPs in the 3D skin model: cytotoxicity, phototoxicity, irritation, and corrosion	Studies focusing on the characterization and synthesis of NPs
Publication type	Reports must contain original data	Articles with no original data (e.g., editorials, reviews, letters) Languages other than Portuguese, Spanish and English Studies published in abstract form only Book chapters